Defence Works Functional Standards 09 - UK · PDF fileDefence Works Functional Standards 09 ... 10 Ground Investigation and Field Testing ... 6.3 Flexible pavement design shall be

Defence WorksFunctional Standards

09Geotechnical Investigationsfor Design and Construction

of Airfield Pavements

Defence Works ServicesMinistry of DefenceLondon: HMSO

© Crown copyright 1994Applications for reproduction should be made to HMSOFirst published 1994

ISBN 011 772813 6

This standard reflects the current practices in Ground Investigation and supercedesAirfield Liaison Memorandum No. 64 (1987) published by Directorate of CivilEngineering Services, Property Services Agency (DOE). The Standard is intendedfor use throughout MOD and shall be used as a guide only.

NOTE:

DEFENCE WORKS FUNCTIONAL STANDARD

GEOTECHNICAL INVESTIGATIONSFOR DESIGN AND CONSTRUCTION OFAIRFIELD PAVEMENTS

CONTENTS

SECTION ONE - GENERAL

1 Introduction2 Definitions3 Scope4 Responsibilities of the Designer5 Design Principles6 Design Practice

SECTION TWO - GENERAL CONSIDERATIONS OFGEOTECHNICAL INVESTIGATIONS

7 Primary Objectives of Site Investigations for Newand Existing Airfield Pavements

8 Design Standards9 Extent and Sequence of Geotechnical Investigations

9.1 General9.2 Desk Study9.3 Ground Investigations and field testing

for Maintenance and Reconstruction ofExisting Pavements

10 Ground Investigation and Field Testing Techniques10.1 General10.2 Drilling, In situ Testing and Sampling10.3 Recommendations for Exploratory Hole Depths

and Spacing10.4 Design Considerations10.5 Remote Methods of Investigation (including Geophysical)

11 Design of Instrumentation and Monitoring12 Geotechnical Investigation Reporting Requirements

12.1 General12.2 Factual Reporting12.3 Interpretative Reporting

13 Soils Classification and Evaluation13.1 General13.2 Soils Classification and Evaluation of Subgrade Strength13.3 General Classification Tests in the Laboratory13.4 Notes on Special Requirements for Testing Contaminated

PAGE No

112234

5

56777

8111111

151618192020202021212223

Soils 26



CONTENTS (Continued) PAGE No

SECTION THREE - DESIGN CONSIDERATIONS

14 Design Parameters

27

2727272831313233333434353535

12131315161717181924253036

12345678910111213

General Methods of Drilling and Sampling TechniquesRecommended Sampling TechniquesClass of Sample QualityRecommended Chemical Sample Preservation and Storage DetailsSpacing of Exploratory HolesSampling FrequenciesMinimum Sample Mass Required for TestingGeophysical Methods of InvestigationCommonly Used InstrumentationRecommended TestingList of General Soils TestingRelative Compaction Requirements for SubgradeList of Recommended Aggregate Testing

Tables

The Modulus of Subgrade Reaction (k)The California Bearing Ratio (CBR)Compaction of Subgrade

15 Design Guidance

14.114.214.3

15.115.215.315.415.515.615.715.8

Subsoil and Subgrade DrainageVery Weak Subgrade (Except Peat)Subgrade ImprovementExpansive SoilsFrost SusceptibilityPeatSpring thaw and permafrostConstruction Practice

16 Aggregates for the Construction of Pavements17 References



FIGURES

1 Effect of Granular Sub-Base on the Modulus of Subgrade Reaction (k) for RigidPavements

APPENDICES

Extended Casagrande Soil Classification and CBR/k Relationship

Table A1 - The Extended Casagrande Soil ClassificationTable A2 - Extended Soil Classification with Material CharacteristicsFigure 2 - California Bearing Ratio versus Modulus of Subgrade Reaction

Standard Cone Penetrometer Interpretation Charts

Interpretation of Pavement Visual Survey Data

CBR versus Soil Suction Curve and Soil Desiccation Potential

A

B

C

D


SECTION ONE - GENERAL

1. INTRODUCTION

1.1 The Defence Works functional standard deals with the investigation of sites forassessing the suitability for the construction of Airfield Pavements and theirassociated structures (such as culverts, bridges, concrete trunking boxes,maintenance areas, hangers and embankments) and of acquiring the geotechnicaland ground contamination characteristics of the site. The objectives of suchinvestigations are to provide information to ensure an economical design andconstruction of the works by reducing to an acceptable level the uncertainties andrisk that the ground poses and ensuring the security of neighbouring land andproperty.

1.2 The detailed design of ground investigation is very important for the accurateidentification and evaluation of the site conditions and pavement formations andcannot be overemphasized.

1.3 This standard does not attempt to cover the wider economic considerationsaffecting the selection of the site, neither does it cover the structural design of theairfield pavement.

2. DEFINITIONS

2.1 Any investigation in advance of construction works, including earthworks shallinvolve considering what is a soil and/or rock and their mechanics. Definitions interms of soils and their testing are given in BS 5930, BS 1377 and BS 6031.Engineering geological descriptions of rocks including the recommended testing arealso given in BS 5930. Unless otherwise stated reference shall always be made tothe latest editions.

2.2 The following terms are specific to this document:

2.2.1 Site Investigation: Determination of physical characteristics of sites as they affectdesign and construction of building and civil engineering works and stability ofneighbouring structures.

2.2.2 Ground Investigation: Exploration and recording of the location and characteristicsof soil and rock, and groundwater conditions.

2.2.3 Designer - The Designer of the site investigation, may be an engineer with a

consultant or a contractor. The Designer shall fulfil the requirements of thedefinition of a Geotechnical Specialist in terms of qualifications and experience(ICE Site Investigation in Construction).

2.2.4 Geotechnical Specialist - A Chartered Engineer or a Chartered Geologist with apostgraduate qualification in geotechnical engineering or engineering geology,equivalent to at least a MSc and with three years post chartered experience ingeotechnics or a Chartered Engineer or Chartered Geologist with at least 5 yearspost-chartered experience in geotechnics. Additional specialist advice on groundcontamination should be provided by an environmental scientist, chemist orenvironmental engineer with a minimum of five years relevant professionalexperience.

3.0 SCOPE

3.1 This standard sets out detailed guidance, formal procedures, technical standardsand gives standard practices (where not covered by other existing standards) forthe assessment, design and construction of Airfield Pavements.

3.2 For the purpose of this standard, ground investigation shall include the following:

desk studysite reconnaissancegeomorphological mappingprocurement of ground investigation contractexploratory fieldworkin situ testing and samplinglaboratory test schedulinginstrumentation and monitoringfactual reportinginterpretative reporting

3.3 The use of soil and rock as construction materials is treated only briefly; andreference should be made to BS 6031: Code of Practice for Earthworks.

4. RESPONSIBILITIES OF THE DESIGNER

4.1 Designers shall be responsible for implementing the requirements of this standardin conjunction with current British Codes, Standards and Practices. The Designershould ensure that:-

an adequate desk study with geotechnical / ground contamination siteinspection is carried out;following the desk study the ground investigation is then planned, designedand directed;appropriate standards of work are then specified;the work shall be properly supervised to ensure that the technical standardsare met;the work is reported in accordance with technical standards.

2

a)b)c)d)e)f)g)h)i)j)

a)

b)

c)d)

e)

4.2 The Designer shall always consult with the Airfield Property Manager beforestarting any works on an existing airfield and before writing any Safetyrequirements specific to a particular site. The Designer shall also consider safetyaspects in accordance with the Construction (Design and Management) Regulations1994, throughout the design process and develop these in the design of the siteinvestigation. These shall include but not be limited to:

3

(a) Effect of work on neighbouring land and structures.(b) Protection of site staff and the public around the site.(c) Access for materials.(d) Access and manoeuvring space for plant.(e) Protection of aircraft and permanent accesses during all stages of the works.(f) Locations of existing services, including drainage, tunnels, electrical,

communication and signalling equipment.(g) Temporary works including shoring of trial pits, scaffolding platforms for

boring rigs.(h) Backfilling of exploratory holes and pits.(i) Protection of monitoring installations

4.3 The Designer shall consult with all Statutory Authorities with regard to thedetermination of the presence or absence of services and any special requirementsof Statutory Authorities (ie: The National Rivers Authority (NRA)).

4.4 Where Made Ground (possibly contaminated) ground is likely to be encountered,the Designer shall carry out a Risk Assessment and COSHH Assessment inaccordance with the Management of health and safety at work regulations (1992).Both statements shall be forwarded to the contractor at the tender stage who shallprepare a separate and detailed COSHH statement for the site work. The Designershall provide the contractor with all available information concerning thecontamination of the site and development history of the site.

4.5 The British Drilling Association (BDA) Guidance Notes for the Safe Drilling ofLandfills and Contaminated Land65, DD 175 Code of Practice for the identificationof potentially contaminated land and its investigation 57, CIRIA report "A Guideto Safe Working Practices for Contaminated Sites", and the ICE Site Investigationin Construction Volume 455 can be used to assist in the preparation of the aboveinformation.

5.0 DESIGN PRINCIPLES

5.1 All pavements are relatively thin constructions, in terms of civil engineeringconstruction, in intimate contact with the ground. The importance of the properapplication of soil mechanics principles depends upon the pavement type and theirlife expectancy. For thin flexible pavements with a thin granular base theinfluence of the soils is very large, whereas for a substantial reinforced concretepavement with a thick sub-base it will be much less so.

5.2 Pavement design requires the knowledge of the application of soil mechanicsprinciples in the design of soil subgrade and granular base layers, together withconcrete and asphalt technology for the bound layers when used. It also requiresthe understanding of the response to repeated wheel loadings (cyclic loadings) andthe influences of environmental effects, notably of ground water changes andclimatic variations (temperature and humidity).

6 DESIGN PRACTICE

6.1 In the late 1970's concrete pavements constructed in the 1950's were reaching theend of their design life. Observation of airfield pavements refined a morecomprehensive fatigue model for calculating the allowable stress in rigidpavements. The designer shall use the model defined in 'A Guide to AirfieldPavement Design and Evaluation58 ', which predicts the appropriate failuremechanism and also allows pavement thicknesses to be related more accurately toload repetitions (cyclic loading).

6.2 The analysis of stresses in rigid pavements shall be based on Westergaard'stheories, and shall have regard to factors such as fatigue by repeated wheelloadings, growth in concrete strength with age and thermal effects such astemperature warping stress. The deterioration with age of lean concrete bases shallalso be considered in line with recent experience.

6.3 Flexible pavement design shall be based on the current UK accepted CBRmethod 13,80 and may use Equivalency Factors in order to take into accountimproved pavement performance given by cement-, lime- and bitumen-bound basecourses77.

6.4 The conventional definitions of rigid and flexible pavements become quite blurredwhen pavements consist of layers of different materials. Mixed constructions areequated to model either rigid or flexible pavement construction on the basis ofmore recent experience of pavement performance. The assessment of multiple slabconstruction is based on an empirical design method developed by the US ArmyCorps of Engineers.

4

SECTION TWO - GENERAL CONSIDERATIONS OF GEOTECHNICALINVESTIGATIONS

7 PRIMARY OBJECTIVES OF SITE INVESTIGATIONS FOR NEW ANDEXISTING AIRFIELD PAVEMENTS

7.1 Adequate ground investigation of a site is essential prior to construction orreconstruction or maintenance of any engineering works especially for airfieldpavements.

7.2 Investigations for existing pavements may be required when any of the followingcircumstances apply:

i) A mid/end of life reassessment of the pavement to plan future maintenancework

and/or rehabilitation;ii) The pavement has been disused for some time and is to be rehabilitated;iii)The pavement is to be strengthened for regular use by heavier aircraft;iv) After several years service it has become apparent that the pavement's strength

has been reduced and it is showing signs of premature failure;v) There has been a change in the classification of the airfield pavement.

7.3 Investigations for airfield pavements can therefore be classified in three differentcategories:

for maintenance of existing pavementsfor reconstruction of existing pavementsfor new construction of pavements

7.4 The investigation of existing pavements for either reconstruction or for the purposeof designing a maintenance program shall be considered in one section of thisStandard.

7.5 The primary objectives of the investigation are to obtain the necessary soilsinformation, distribution and physical properties/characteristics and may besummarised as follows:

for existing pavement evaluation the details of the pavement design arerequired;the underlying subsoil condition and characteristics;for the construction or reconstruction of new pavements the suitability of thesite;to provide geotechnical data including chemical and environmental data foran economic, safe and reliable design of the works including any temporaryworks and interaction/effects of any previous land use;

i)ii)iii)

i)

ii)iii)

iv)

5

v) assessment of problems and constraints associated with the works, which mayinclude:

Pavement (foundation) designSubgrade (soil) conditions and characteristicsGroundwater conditions and seasonal variationsEarthworks, trafficability and temporary worksEffects of previous land useBuried structures or cavitiesGround and groundwater contamination

8.0 DESIGN STANDARDS

8.1 All site investigation shall be in accordance with BS 5930 and all laboratory testingin accordance with BS 1377. Chemical testing of soils and groundwaters forcontamination shall be in accordance with methods published by the StandingCommittee of Analysts (DOE), or the US Environmental Protection Agency(USEPA). All analytical and soils laboratories shall be NAMAS accredited, or beable to demonstrate compliance with an equivalent quality standard. Referenceshould also be made to the CIRIA Site Investigation Manual56 for detaileddescriptions of site investigation techniques.

8.2 The ground investigation specification shall be in general accordance with the ICESpecification for Ground Investigation.

8.3 The Designer shall use a formal documented quality management systemcomplying with the principles of the British Standard for Quality Systems BS 5750.

9.0 EXTENT AND SEQUENCE OF GEOTECHNICAL INVESTIGATIONS

9.1 GENERAL

9.1.1 Geotechnical investigation is an essential part of all civil engineering projects,which will provide information to evaluate and characterise the interaction of theproposed and or existing airfield pavements and the sub-surface soils. In someinstances an evaluation of sub-surface contamination will also be appropriate.

9.1.2 It is essential that an adequate investigation of the on site soil conditions and theircharacteristics is carried out prior to the design and construction or reconstructionof new airfield pavements and associated structures together with establishing thedesign details of any existing pavements or structures. For new or reconstructedpavements any investigation shall include:

A desk study of all existing information, including a literature and statutoryarchives searches and any existing pavement details (if available)Site Reconnaissance survey (walk-over), including visual condition surveysof existing pavements and any contaminationTopographical and structural surveys (where necessary)A ground investigation to determine the sub-surface soil profile of differentlayers with relation to the proposed earthworks and subgrade evaluation.Obtain sufficient representative disturbed and undisturbed samples of eachlayer of the soil profile.Carry out sufficient in-situ and laboratory tests on representative samplesto determine the physical, geotechnical and chemical characteristics of thevarious soil types, with respect to the in-situ density, compressibility, shearstrength, drainage properties contaminative potential and whether the soilsare susceptible to expansion or frost heave.A survey to determine the availability and suitability of materials for re-usein construction.

9.2 DESK STUDY

9.2.1 The desk study is an essential part of the investigation for new work,reconstruction or repairs/maintenance to existing airfields and their associatedstructures, when developing an understanding of ground conditions and possiblegeotechnical, constructional or environmental problems.

9.2.2 Desk studies shall search for all existing relevant information on the site and 'as-built' drawings of any existing pavements. A detailed list of sources for obtaininginformation may be found in BS 5930, section 4.2 and appendices A and B andDD 17557. In addition the following authoritative bodies shall be consulted;Airfield Properties Manager, National Rivers Authority (NRA), Waste RegulationAuthority (WRA), Environmental Health Department records for any previousknown pollution incidents, Department of Environment Cavities Database, CountyRecords Offices and Land Agent Landfill Registers.

7

9.2.3 Aerial photographs shall be consulted as an important method in evaluating newconstruction sites and may assist in studying existing sites often identifyingproblems not visible at ground level, for a detailed description of their use referto TRRL report81 and Working Party Report QJEG82.

9.2.4 Careful appraisal of a desk study in conjunction with the proposed development orreconstruction shall be undertaken. This will often indicate the types and amountsof subsurface investigation required, and is a very cost effective way of designinga ground investigation.

9.2.5 The Designer shall carry out a site reconnaissance at an early stage in the designwhich should aim to cover as large an area as possible in the time allowed. Theadjacent structures may yield valuable information with regard to the behaviour ofsoil-structure interaction. Should any nearby structures show signs of distress, itis highly recommended that information with regard to their design is obtained andanalyzed. Guidance on site reconnaissance in respect of contaminated land is givenin BS: DD 175 section 4.3.

9.2.6 The Designer shall prepare a desk study report which shall supply a proposedcontents list similar to but not restricted to:

introductionthe site and proposed construction worksgeology (including available existing borehole information)topography and geomorphologydrainage and hydrogeologypresent land-use and site historypotential for ground contaminationwalk over survey and/or visual condition surveylaboratory testing when available (from previous ground investigations)engineering considerationsconclusions with recommendations for the detailed site investigation wherenecessaryall as-built data and drawings of existing airfield pavements if available

9.3 GROUND INVESTIGATIONS AND FIELD TESTING FOR MAINTENANCEAND RECONSTRUCTION OF EXISTING PAVEMENTS

9.3.1 Evaluation of existing pavements shall include the following:

i) Ascertaining the existing construction detailsii) Ascertaining the condition of the existing pavementiii) Ascertaining the material properties of subsoils and the pavement

construction materials

9.3.2 Evaluation of the existing construction details shall be by review of 'as-built'drawings together with the 'specification' and 'feed-back' reports. If records arenot available then field work will be required in the form of exploratory holes, toinvestigate:

8

a)b)c)d)e)f)g)h)i)j)k)

l)

Techniques Parameters to be assessed

Pavement Construction :

- Rotary Cores- Falling Weight

Deflectometer- Plate Bearing Test- Deflection Beam

(Benkelman Principle)

Subgrade Construction :

Trial pits/Boreholes

Dimensions/thickness of pavements layers

Elastic Modulus

Thickness of subgrade and material quality

Soils profile

9.3.3 Evaluation of the condition of the existing pavement shall follow the guidelinesdetailed in the 'Design Manual for Roads and Bridges', Volume 7, Section 3, Part2, "Visual Condition Surveys". All defects such as ruts and cracking shall benoted and sketched. Surveys of concrete pavements shall whenever possible becarried out in cooler months, when cracks are more noticeable and when theefficiency of joint seals can be better assessed (see Appendix C). The use of non-destructive deflection tests can be used in the assessment of pavement bearingcapacity and support condition; with tests carried out at slab centres and along thejoints, a fair appraisal/evaluation may be made, which may allow the design ofremedial measures or any necessary maintenance measures.

9.3.4 Evaluation of material properties within the pavement construction and subsoils,shall be by review of 'as-built' drawings together with the 'specification' and 'feed-back' reports. If records are not available then field work will be required in theform of exploratory holes, to investigate:

9

9.3.5

9.3.6

Techniques Type ofpavement

Parameters to be assessed

Pavement Construction

Rotary Cores* see section 16

Flexible Marshall TestBitumen ContentParticle Size Distribution

Rigid Visual DescriptionPetrographical Analysis

Subsoils / Subgrade

Trial Pits / BoreholesPlate Bearing TestFalling Weight DeflectometerDeflection Beam

Flexible andRigid

Soil Material CharacteristicsDegree of CompactionSubgrade Reaction (Modulus)Compressibility

* see section 10.2

* see section 11

Instrumentation and Monitoring

Flexible and GroundwaterRigid

See section 10 for a more detailed descnption of the evaluation of subsoils.

Evaluation of the subsoils by exploratory holes (fieldwork) is described in detailin the following sections:

Methods of InvestigationDesign of Instrumentation and MonitoringSoils Classification and Evaluation

Evaluation of aggregate properties for pavement construction is described insection 16.

10 GROUND INVESTIGATION AND FIELD TESTING TECHNIQUES

10.1 GENERAL

10.1.1 If a ground investigation is required it shall be designed to verify and expand onthe previously collected information reported in the Desk Study. The report shallbe a means of providing the information necessary for a safe and economicaldesign, to identify potential construction problems and hazards. In additionconsideration shall be given to acquisition and assessment of geotechnical andground contamination data throughout the construction period, in order to checkthat actual ground conditions are as assumed during the design.

10.2 DRILLING, IN SITU TESTING AND SAMPLING

10.2.1 The Designer shall consider all appropriate methods of investigation, whendesigning a site investigation. The following Table 1 gives the most commonlyused methods of forming exploratory holes, sampling methods and in situ testing.Table 2 gives recommendations for appropriate methods of sampling for differenttypes of soils and rocks based upon the classification of sample quality given inTable 3.

10.2.2 Some of the methods of ground investigation are classed as engineering operationsand therefore come within the definition of "development" as defined in the Townand Country Planning Act 1990". However, in the vast majority of cases theseactivities are likely to be small scale/low key engineering operations which wouldnormally be regarded as "de minimimis" in town planning terms and not requireplanning clearance under DOE Circular 18/84 (or it's equivalent in Wales,Scotland and Northern Ireland). In cases of doubt, it is always open to theDesigner, after first consulting the local Defence Land Agent, to approach the localplanning authority for confirmation that the proposed investigation works do notrequire planning clearance.

TABLE 1 - General Methods of Drilling and Sampling Techniques

Boreholes

Trial Pits

HandAugering

Pressuremeter

DynamicProbing

ContaminatesTests

Light CablePercussion

Rotary FlightAuger

Rotary Coring

Rotary Percussion(Openhole/WashBoring)

Static ConePenetrometer

Continuous SoilSampler

Slotted Standpipe(50mm int. diam.)

Machine or handdug

Selfboring,attached to CPT

IN SITU SAMPLING

U 100mmPistonDisturbed(Rotary Pendant Cores)Bishop Sand Sampler

(U 100mm)(Piston)Disturbed(Bishop Sand Sampler)

(U 100mm)Cores

(U 100mm)(Disturbed)Chippings

Gas/Water sampler,Continuous Soil

U(35-50mm)

Water sampler

Disturbed

(Piston)

U(38mm) hand driven

Block Samples

(Disturbed)

Glass/tin Jars (Disturbedsoil)Glass Jars (water)

IN SITU TESTING

Standard Penetration TestBorehole shear vaneBorehole Plate Bearingtest strength,Permeability

Standard Penetration TestPermeability

Standard Penetration TestPermeability

Standard Penetration Test

PressuremeterPiezocone

Description Only

Gas, water and soilanalyzers

Hand Shear Vane

Hand Penetrometer

Mexe-probeCalifornia Bearing Ratio

California Bearing RatioPlate Bearing TestSoakaway /Permeability

Description only

Shear ModuliPorewater Pressure

Relative Densities

Gas AnalyzersPortable soil/gas/waterchronograph

REFERENCE

BS 1377: Part 9BS 1377: Part 9BS 1377: Part 9

BS 5930

BS 1377: Part 9BS 5930

BS 1377: Part 9BS 5930

BS 1377: Part 9

BS 5930CIRIA83

CIRIA56

BS DD175

BS 1377: Part 7

CIRIA56

ref85

BS 1377: Part 4

BS 1377: Part 4BS 1377: Part 9BS 5930

BS 5930

CIRIA90

BS 1377: Part 9

BS (DD 175)

BS (DD 175)

12

TABLE 2 - Recommended Sampling Techniques

Type ofSamples

(size)

U(l00mm)Undisturbed

Thin wall piston(100mm)(250mm)

Bishop SandSamples

Disturbed(<1kg)

Disturbed Bulk(<25kg)

Rotary Cores

U(38mm)

Block samples(> 400mm)

StandardPenetration Test

Cohesive(strength values Cu)

Strength <50kN/m2

< 100kN/m2

> 100kN/m2

< 100kN/m2

<75kN/m2

not applicable

Dependent upon bitand technique

<50kN/m2

>50kN/m2

>75kN/m2

Its use is difficult infills and made ground

Class ofSample

11-23-4

11

-

3-5

2-5

2-5

12-3

1-2

4-5

Non-Cohesive

Silts and finesands

Silts and finesands

Silts and sands

Clayey silts andclayey sands

Clayey silts

Beware of pipingand water table

Class ofSample

3

1

2-3

3-5

2-5

-

-

2-5

4-5

See BS 593053 and CIRIA56 for further explanation of the above techniques.

TABLE 3 - CLASS of Sample Quality

Class 1

Class 2

Class 3

Class 4

Class 5

Index tests, natural moisture content(NMC), density, strengthcharacteristics

Index tests, NMC, particle size distribution(PSD), density andstrength

and deformation

remoulded

Index tests, NMC, PSD

Index tests

Strata identification only

See BS 593053 and CIRIA56 for further explanation.

13

10.2.3 The general investigation techniques used for airfield pavements are light cablepercussion and trial pits. It should be noted that backfilling of trial pits must becarefully backfilled in thin layers with suitable compaction by the excavator orcompaction equipment in order to avoid long term settlement of the reinstatement.For a detailed description of the most commonly used techniques and in situ testingmethods see CIRIA SP25 'Site Investigation Manual'56, and BS 593053 'Code ofPractice for Site Investigation'

10.2.4 Where samples are being collected specifically to identify and measure thepresence and concentrations of contaminants the issues of cross contamination andsample disturbance should also be considered. For example, although trial pitsprovide a good visual examination of ground conditions, the excavation processwill tend to mix materials, particularly if groundwater is present, and so lead tocross contamination. Similarly if volatile organic compounds are of interest thedisturbance to the ground caused by trial pitting may cause significant losses ofthese compounds prior to sampling. The appropriate use of pressure washers orsteam cleaners should also be considered on contaminated sites to minimise thepotential for cross contamination both between exploratory holes and withinindividual holes.

10.2.5 On contaminated sites the characterisation of the hydrogeology and groundwaterchemistry is often a fundamental requirement. This is generally undertaken by theuse of borehole into which piezometers or standpipes are subsequently installed.Depending on the geological context, a number of groundwater bodies may bepresent at different depths and the investigation technique selected should ensurethat cross contamination between separate water bodies does not occur. This isimportant both to ensure that representative samples are collected and to preventthe creation of migration routes by which contamination of groundwater mayoccur.

10.2.6 Samples of soils for chemical analysis should be of a minimum volume of 1 litreand in most circumstances glass or plastic (polypropylene or polyethylene)containers will be suitable for storing samples prior to analysis. All containersshould be clean and dry prior to use and filled with air/water tight lid. Wheresubsequent analysis is to include volatile organics' a sealed steel or aluminiumcontainer should be used. Containers should be completely filled with the soilsample to minimise the opportunity for oxidation of contaminants during transit tothe laboratory. The chemical composition of ground and surface water samplescan alter relatively following collection. To minimise this effect water samplesshould always be analyzed as soon as is practicable after collection.

10.2.7 Deterioration of water samples can be reduced by chemical preservation of thesample immediately after sampling. Details of appropriate preservatives, samplecontainers and sample volumes are given in table 4. In addition, wherever possiblean unfixed one litre sample should be collected in an amber glass bottle.

10.2.8 Water samples, both fixed and unfixed, should be maintained at a cool temperature(approximately 4°C) prior to arrival at the analytical laboratory. The use of coolboxes and ice packs is a practicable means of ensuring that samples are kept at an

14

appropriate temperature during transit.

10.2.9 In situ testing for contaminants is generally restricted to the use of portableinstruments to identify and measure soil gases. These range from relatively simplehand held instruments for measuring the principal components of landfill gas to theuse of mobile gas chromatographs for determining the concentrations of individualvolatile organic compounds (VOC's).

10.2.10 In addition a range of portable test kits are available which can be used in the fieldto provide indication of certain contaminants in soil and water samples (ex situ on-site testing). Generally such kits are used to provide a preliminary indication ofthe presence of contaminants and are combined with the use of conventionallaboratory analysis.

TABLE 4 - Recommended Chemical Sample Preservation and Storage Details

Bottle type and size Analytical Parameter Fixative

Polyethylene 1000ml ammonical nitrogen, nitrate

chemical oxygen demand,total organic carbon,phenols

Addition ofless than 2

Polyethylene 150ml sulphide Addition of 2.5ml of 5ml/lNaOH solution with zinc acetatecrystals added at a concentrationequivalent to 1g per litre ofsample

Polyethylene 150ml cyanide Addition of NaOH until pH isgreater than 12

Borosilicate glass withPTFE sealed cap500ml

metals Addition ofsample until

10.3 RECOMMENDATIONS FOR EXPLORATORY HOLE DEPTHS AND SPACING

10.3.1 Exploratory hole depths and spacings should be considered only after evaluatingthe past site history and desk study report. Exploratory holes should target areasof special interest, however a suggested minimum spacing is given in Table 5.Monitoring of groundwater and its movement is an essential part of anyinvestigation. Observations over several months may be necessary to establish anyseasonal variations and preferably over a period of at least one year.

15

to filteredPh is less than 2

H2SO4 until pH is

TABLE 5 - Spacing of Exploratory Holes

LocationRunways and Taxiways

Aprons and other areas

Borrow areas

FrequencyBoreholes 1 every50 Linear metres *

(Staggered acrossthe proposedcentre line)

Trial pits 1 every50 Linear metres *

(Staggered as a chequered patternalternatively at sides of proposedpavements)

Boreholes and Trial Pits positioned on a 60m square gridtrial pits positioned on a 30m square gridPositioned on a grid defined as 2% of the total squarearea, for a preliminary investigation. Otherwisepositioned to sample at 1000m2 square grid spacings

* Boreholes or Trial Pits may both be used depending on the ground conditions.** Table revised from PSA, " A Guide to Airfield Pavement Design and

Evaluation" 58.

10.3.2 The spacing of exploratory holes for the purposes of assessing groundcontamination should relate to both the objectives of the study and knowninformation on site history and geology. Some limited guidance on spacings fora detailed investigation of contaminated land and appropriate sampling patterns isgiven in British Standards Institution, Draft for Development DD:175.

10.4 DESIGN CONSIDERATIONS

10.4.1 The Designer shall consider the in situ testing, sampling frequency and type andquality of samples required in each anticipated stratum to achieve the adequatecharacterisation of the material and determination of the required geotechnicalproperties for use in the temporary and permanent works design.

10.4.2 Ground investigations involving exploratory holes will require in-situ representativesampling of the subsoils. The type of sampling and frequency will depend uponthe characteristics of the sub-soils and type of construction proposed. Generally,all soils whether within the United Kingdom can be subdivided into seven groups(see Appendix A, Table Al). Table 6 - shows typical sampling frequencies forvarious subsoil conditions and should be used in conjunction with Table 7 -'Minimum sample mass required' when designing an investigation.

10.4.3 For contaminated sites, British Standards Institution Draft for the DevelopmentDD: 175 recommends a minimum of three samples to be taken from each samplinglocation (ie: trail pit, borehole etc). In practice it is better to over sample at thetime of the investigation even if not all the samples collected are subsequentlyanalyzed. At least one sample shall be collected of each type of materialencountered and generally samples shall be collected at 0.5m intervals.Groundwater shall always be sampled when encountered.

16

TABLE 6 - Sampling Frequencies

SOILS GROUP SAMPLE TYPE BOREHOLES TRIAL PITS

Cohesionless Soils Disturbed (<1kg)

Disturbed (<25kg)Water SampleStandard Penetration testPermeability

Every 1m and change instratumEvery 1.5 linear metreEvery water strikeEvery 1m depthOne in 2 boreholes

3 to 5 no per pit

3 to 5 no per pitEvery water strike

(3 for 500m3 earthworks)

Cohesive Soils Disturbed (<1kg)

Disturbed (<25kg)Undisturbed (100mm/piston orblock)Standard Penetration test

PermeabilityWater Sample

Every 1m and change instratumEvery failed undisturbedEvery 1 linear metre

Every other undisturbedsample when recoveringless than 65 %1 per boreholeEvery water strike

3 to 5 No per pit

3 to 5 no per pit(3 for 500m3) in weakrocks or cohesive material

(3 for 500m3 earthworks)Every water strike

Made-Ground (Fill) (As per cohesiveor non-cohesive soils)

Specialist Chemical testing (water)(soil)

3 per water table3 for 1000m3 earthworks

3 per watertable3 for 1000m3 earthworks

Moisture content(*when tree/shrubclearance or whensoils may besaturated or subjectto drying out

Disturbed (<1kg) Every 0.5 linear metre Every 0.25 linear metre

TABLE 7 - Minimum Sample Mass Required For Testing

PURPOSE OF SAMPLE

Soil identification (including Atterberg limits, sieveanalysis, moisture content, sulphate, chloride, Phvalue, organic content).

Compaction tests (Maximum DryDensity/MCV/CBR)

Frost heave

Comprehensive examination of construction,materials, including soil stabilisation

Specialist Chemical Tests

SOIL TYPE

Fine grainedMedium grainedCoarse grained

ALL

ALL

Fine grainedMedium grainedCoarse grained

All SoilsWater

MASS OF SAMPLEREQUIRED

2.5kg7.0kg40.0 kg

80.0 kg

80.0 kg

100kg130kg160kg

200 gm2 Litres

17

10.5 GEOPHYSICAL METHODS OF INVESTIGATION

10.5.1 Investigations for new airfield and maintenance of existing pavements may be mademore cost effective when the traditional boreholes and trial pits are used inconjunction with recent advances in investigation methods such as remote sensing(Geophysics) and static cone penetrometer techniques to investigate anomalies inthe subsoil or existing pavement structural conditions. A modified version of theSCPT rig can also be used for collecting discrete samples of soils, groundwaterand soil gases for chemical analysis.

10.5.2 The following Table 8 - Geophysical methods of Investigation summarises therecommended use of maximum probable depths of penetration and the probabilityof success for the technique, in defining the extent and type of any anomalyinvestigated.

TABLE 8 - Geophysical Methods of Investigation

RECOMMENDEDUSE/PROBLEM

Buried obstructions and cavities

Identifying boundaries to landfill ormade ground

Identifying Bedrock interface withsuperficial deposits(ie:- Clays/bedrock)

Subsurface interface between soillayers(ie:- Peat/Sand)

Groundwater boundary

Existing pavement

ADVANCED METHOD OFINVESTIGATION

Geophysical - Magnetometer- InducedConductivityGround radar

Geophysical - Refraction- Resistivity- Magnetometer- InducedConductivityGround Radar

Geophysical - Refraction- Resistivity- InducedConductivity

Static cone penetrometer

Geophysical - Refraction- Resistivity- InducedConductivityGround Radar

Geophysical - Resistivity

Ground Radar

Notes: *1 Depth of penetration depends upon reaction weight and stiffness of the materials penetrated.*2 Dependent upon the contrast in resistance of the materials and type of fluid medium*3 Subject to interpretation between exploratory hole locations

10.5.3 The use of these methods involves investigating the area of interest by traversingthe area usually on grid basis. The spacings are very dependant upon the natureof the problem being investigated. It is highly recommended that on siteinterpretation of geophysical techniques is always carried out, in order for them tobe most economically cost effective and to determine whether any additional

18

<5m

5m to 10m

<20m<15m

<30m< 6m

<20m<15m

5m to 10m20m to 35m

5m to 10m5m to 6m

5m to 20m

5m to 10m5m to 6m

5m to 10m5m to 6m

5m to 20m 40%

35%70%

40%40%30%

45%55%

70%55%

40%95%

70%55%

35%70%

50%

90%

MAXIMUMDEPTH OF

PENETRATION

PROBABILITYOF SUCCESS

traverses are required to investigate anomalies before the Contractor leaves site.

10.5.4 The use of geophysical techniques will require exploratory holes for the calibrationof the equipment and to assist in the interpretation of the results.

10.5.5 It is recommended that when considering the use of recent advanced techniquesthese should be planned to be used in conjunction with and at a very early stagein the field/site works. This will allow for input and fine tuning of the positioningof exploratory holes investigating anomalies within the subsoil and existingstructures.

11 DESIGN OF INSTRUMENTATION AND MONITORING

11.1 The designer shall consider the necessity for and purpose of the instrumentationand then select the most appropriate type based upon the reliability andapplicability of the various instrumentation methods. The following Table 9. givesa short summary of commonly used instruments for airfield pavements andearthworks together with their most suitable applications.

TABLE 9 - Commonly used Instrumentation

Instrument Application

GroundwaterMonitoring

(see note below)

Settlement Monitoring

Type of Instrument

Pneumatic Piezometer

Hydraulic Piezometer

Electrical Piezometer

Open Standpipe

(minimum 50mm Int.Diam.)

Hydraulic plates andtubes

Magnetic Extensometer

Pneumatic SettlementGauges

Comments

Gas powered may bemonitored remote from the

Borehole

Water filled and subject tofreezing. Can carry out

Permeability tests at a laterdate

Can be monitored remote ofthe site by radio transmission

Allows water samples to betaken at a later date, and most

cost effective

Measures settlement underembankments

Measures settlements withinand below large embankments

Measures settlement underembankments

19

11.2 For groundwater monitoring the Designer shall determine the anticipatedpermeability of the various strata likely to be encountered based on the findings ofthe desk study, then consider the likely response times of any groundwatermonitoring instruments and the appropriate types of instrument that should beinstalled to enable detection of groundwater fluctuations.

11.3 The Designer shall consider the commissioning of the instruments (base readings)and determine the frequency of monitoring of the instruments. The frequency shalltake into account the stability of the readings including any seasonal or diurnalfluctuation in the measurements. The requirements for long term monitoring shallbe determined by the Designer after consultation with all relevant Authorities(NRA, Local Waste Department, Airfield Property Manager, etc).

11.4 For ground deformation monitoring, the strength of the surrounding ground shallbe closely reflected by the strength of any grouting around the installation ofinstruments. The desk study should also provide the required length of fixity toensure a good stable datum or base to the instrument is provided.

11.5 For gas monitoring, the Designer shall refer to CIRIA Report N° 13167 Themeasurement of methane and other gases from the ground'

12 GEOTECHNICAL INVESTIGATION REPORTING REQUIREMENTS

12.1 GENERAL

The results of the ground investigation shall be presented in two reports

factual reportinterpretative report

12.2 FACTUAL REPORTING

12.2.1 The Contractor shall be instructed to supply the ground investigation data in digitalform in accordance with the ACS publication "Electronic transfer of geotechnicaldata from ground investigations"64.

12.2.2 The contents list of the factual report shall include but not be restricted to:

introduction with project details and referencethe site details, referenced to OS grid referencefieldwork, including details of methods of investigation, in situ testingand sampling, groundwater level monitoring and observations,exploratory hole ground levels and national grid coordinateslaboratory testingdrawings, including key plan, exploratory hole location plans andgeological sections, where appropriate

20

a)b)

a)b)c)

d)e)

12.3 INTERPRETATIVE REPORTING

12.3.1 The Designer shall whenever possible prepare the interpretative report. Thecontents list of the interpretative report shall have a contents list which shallinclude but not be restricted to:

introduction - purpose of report, participants, scope of workthe site referenced to OS grid reference and proposed constructionworksgeneral geology, site conditions and history (brief summary of deskstudy report)fieldworklaboratory testingground and groundwater conditions including environmental/chemicalaspectsgeotechnical parameters for designmonitoring resultsmethods of analysisengineering considerations, including results of slope stability analysis,interpretation of failure mechanisms, possible remedial measures,ground improvement, tunnelling, foundation design, site preparation,sources, re-use of materials and identification of environmental effectsprovide a range of design solutions and recommendations withguidance on which might be most appropriate in terms of cost, timing,ease of construction, future maintenance etc.recommendation and conclusionsreferencesdrawings, including exploratory hole location plans and interpretatedgeotechnical sections.

12.3.2 A separate section shall also report any ground contamination test results andconclusions; indicating the following:

any significant contaminantsenvironmental liabilities with the siteany necessary constraints on constructionremedial optionshealth and safety issues

12.3.3 Copies of all calculations shall be included as an appendix to the report.

13.0 SOILS CLASSIFICATION AND EVALUATION

13.1 GENERAL

13.1.1 Thorough evaluation of the subgrade is very important, especially for flexiblepavements where the required thickness depends greatly on the shear strength ofthe soil. This evaluation of the subgrade includes the determination of subgradestrength and the assessment of factors which can affect the stability of the subgrade

a)b)

c)

d)e)f)

g)h)i)j)

k)

1)m)n)

a)b)c)d)e)

21

with time: e.g. shrinkage and swelling, frost action and mud pumping. It is alsoimportant to ascertain the vertical profile of the soil types, densities and moisturecontents.

13.2 SOILS CLASSIFICATION AND EVALUATION OF SUBGRADE STRENGTH.

13.2.1 The soils classification by visual method is described in detail in BS 5930: Section8, clause 42 and is based upon the Casagrande System (1942). A summary tableis included in Appendix A. For classification the group symbols used for coarsegrained soils are derived by particle size distribution and those for fine-grainedsoils are mainly derived from the plasticity index and liquid limit. The tests usedto determine these groups are described fully in BS 1377. The BS 5930, SoilsClassification System enables the soils to be assessed for its likely behaviour as asubgrade, including its shear strength, shrinkage, drainage properties andsusceptibility to frost heave. Although an experienced engineer can often estimatethe shear strength and load-deflection values for a subgrade from the classificationtests, it is often necessary to carry out further tests specifically to measure thesecharacteristics.

13.2.2. The subgrade strength characteristics required for pavement design are theModulus of Subgrade Reaction (k) and the California Bearing Ratio (CBR) forrigid and flexible pavements respectively. The design values chosen must berepresentative of the soil under the pavement after construction. Therefore, theyshould be based upon a relevant moisture content and density.

13.2.3 In selecting a design moisture content, consideration must be given to seasonalvariations and likelihood of the post-construction moisture content being higherthan the pre-construction in situ value.

There are some useful guidelines for certain conditions:

A method of ascertaining the post-construction moisture content is toexamine the subgrade under an existing adjacent pavement. The accuracyof the assessment will depend upon the similarity of pavement widths,subsoil drainage and permeability of the surface layers.

In very dry climatic conditions, if no water is present, the in situ value ofthe natural subgrade is likely to be representative.

In cohesive soils which are homogeneous with depth, TRRL suggest Ref 18

that the moisture content at 1m below ground level may be representative,but that a moisture content profile to prove any desiccation of the upperlayers is carried out to confirm.

In the absence of any other information the moisture content of cohesiveUK soils, except those containing a high proportion of montmorillonite,seldom exceeds the plastic limit plus 3 %.

(i)

(ii)

(iii)

(iv)

22

13.2.4 Selection of a representative density will depend on the in situ density, and thedegree of compaction likely during construction (see Section 14.3).

13.2.5 The test for the Modulus of Subgrade Reaction (k) is a large scale in situ test,which measures the behaviour of the subgrade as a whole and therefore tends tocompensate for variations of the density and moisture content with depth. TheCBR test only measures the properties of a very small volume of the subgrade andit is more difficult to find a representative design value. However, in practice theModulus of Subgrade Reaction test is difficult to carry out and in some situationsit may be sufficient to assess k from the CBR value. Appendix A includes anapproximate relationship between CBR and k. Use this with caution, particularlywhen considering soils uncommon in the UK (e.g. Laterites, corals and volcanicclinker/ash).

13.2.6 The Shear Modulus of subgrade/subsoils may also be determined by pressuremetersand self-boring pressuremeters; which are recommended by this standard inpreference to pressure tests in boreholes, due to the general ground disturbancearound boreholes. Pressuremeters may also be used in combination with staticcone penetrometers (CPT).

13.2.7 The Elastic Shear Modulus90 (G) of soils may be derived from the unload-reloadcycle of the test, which may be converted to Young's Modulus (E), for eitherdrained or undrained conditions. The drainage conditions shall be for design/fieldconditions not those of the test and the value calculated is independent of testconditions. The test cycle should be conducted at a late stage in the test, at a testpressure in excess of the in situ pressures, in order to obtain a good representativevalue for Elastic Modulus.

13.2.8 In most cases soils and weak rocks are assumed to behave in an isotropic mannerfor the determination of vertical behaviour and deformation, however, modulidetermined from pressuremeter tests obtained in the horizontal plane (attitude);shall be carefully reviewed90 when considering either highly over-consolidated soilsor weak rocks, both of which display high degrees of anisotropic behaviour.

13.3 GENERAL CLASSIFICATION TESTS IN THE LABORATORY

13.3.1 All samples should be visually described prior to testing, and upon each subsequentspecimen taken from the sample.

13.3.2 When designing a laboratory testing sequence a list of required design parametersand representative tests for each soil type should be drawn up. It is essential tocheck the amount of material available before testing in case there is insufficient,see Table 7.

23

13.3.3 A summary of the basic tests for Airfield Pavement Design is given in Table 10below:

TABLE 10 - Recommended Testing

SOILTYPE

Soft to firmclays

Firm to stiffclays

Gravellyclays

Sands

Gravels

Weak Rocks

CLASSIFICATION TESTS

Moisture content liquid, plastic,shrinkage limits. Bulk density

Moisture content liquid, plastic,shrinkage limits. Bulk density

Moisture content, liquid andplastic limits on material passinga 425 micron sieve. Bulkdensity. Particle size distributionand sedimentation

Maximum and minimum densitiesand particle size distribution. Insitu density

As Above

Bulk density, specific gravity,moisture content, point load tests,disc test, petrological examination

OTHER LABORATORY TESTS

Quick undrained triaxialcompression test and vanes in softclays. Consolidation oedometer(Swell test)

Quick undrained or consolidatedundrained triaxial compression testwith pore pressure measurement foreffective stress parameters.Consolidation oedometer.

Unconsolidated undrained triaxialtest on 100mm specimen

Direct shear box for range ofdensities

As Above

Uniaxial compression tests andquick undrained triaxial

REMARKS

Refer to in situ CPTand Pressuremeter

Refer to in situ CPTand Pressuremeter

Refer to in situ testsof SPT, static cone,plate test, CBR.

As Above

Shear box tests oncut or natural planes/ discontinuities maybe useful

13.3.4 Together with the standard recommended tests for soils summarised in the Table11 the following tests listed below are essential for the design of airfieldpavements:

Atterberg Limits and Soil ClassificationCompaction test (with hand vane values at each Proctor point in cohesivesoils)California Bearing Ratio (CBR) / Resilient ModulusPermeability testsMoisture Condition test (MCV)Frost Susceptibility

For detailed descriptions of the tests the reader should refer to BS 1377, "British

24

TABLE 11 - List of General Soils Testing

TestDescription

Laboratory Tests

Natural Moisture Content

Atterberg Limits

Organic Matter

Total Sulphates and SolubleSulphates

Ph value

Chloride Content

Compaction dry density /moisturecontent relationship

Bulk Density

California Bearing Ratio

1-D Consolidation Properties

Unconfined Compressive Strength

Consolidated Drained TnaxialCompression

Permeability (Constant Head)

DispersibilityPinhole testCrumb test

Dispersion Value test

Frost Susceptibility

Chalk Crushing Value

Moisture Condition Value

Particle Size Distribution (PSD)

Hand Vane

In Situ

California Bearing Ratio

In situ Density

Standard Penetration Test (SPT)

Plate Bearing Test

Pressuremeter

Recommended Standard forTest

DesignParametersfrom Test

Statistical Number required forconfidence Limits

Low Medium High

BS 1377:Part 2,Clause 3.2

BS 1377:Part 2,Clauses 4 and 5

BS 1377:Part 3,Clause 3




BS 1377: Part 4,Clause 3





BS 1377:Part 8,Clause 7 (with ru)Clause 8 (without ru)


BS 1377:Part 5,Clause 6.2Clause 6.3Clause 6.4

BS 1377:Part 4, Clause 7 andBS 812:Part 124





nmc

LL,PL,PI,LI

Potential aggregate andconcrete attack



Maximum Dry Density,Optimum Moisture

Content

Bulk Density, DryDensity

CBR%, OptimumMoisture Content,

Maximum Dry Density

Degree of Dispersibility


CCV

MCV Value,Relative Density

Grading Curve,sizes of aggregate

panicles

cu

1

3

1

1

1

1

3

1

3

1-3

1-3

1-3

1-3

1-3

9

1-3

1-3

1-3

5

BS 1377:Part 9,Clause 4.3



BS 1377:Part 9,Clauses 4.1

CIRIA90

CBR Value %

Relative Density,(nmc)

N Value,(Relative Density)

Modulus of SubgradeReaction (k)

Shear Modulus

1-3

1-3

3

1

1

2

6

3

3

2

3

6

3

6

6

6

6

6

6

18

6

6

6

10

3

9

6

6

4

6

9

6

9

9

9

9

9

9

27

9

9

9

15

6

6

6

"-

9

9

9

3

3

25

Standard Methods of Test for Soils for Civil Engineering Purposes"16.

13.4 NOTES ON SPECIAL REQUIREMENTS FOR TESTING CONTAMINATEDSOILS

13.4.1 General guidance on the selection of appropriate testing requirements forcontaminated land is given in ICRCL 59/8370. In practice the testing requirementsshall be related to both the historical use of the site and the observations madeduring the course of the investigation. Depending on these factors a very widerange of contaminants could be of interest including inorganic and organicchemicals, asbestos, radioactive materials and pathogenic organisms.

26

SECTION THREE - DESIGN CONSIDERATIONS

14 DESIGN PARAMETERS

14.1 THE MODULUS OF SUBGRADE REACTION (k)

14.1.1 The Modulus of Subgrade Reaction (k) covers the determination of the verticaldeformation and strength characteristics of soil in situ by assessing the force andamount of penetration with time when a rigid plate is made to penetrate the soil.See British Standard BS 1377: Part 9: 1990, test 4.1 for a full description of thetest method.

14.1.2 Interpretation of the results is carried out by plotting the pressure on the plateagainst settlement and the k value is taken as the slope of the line passing throughto the origin and the point on the curve corresponding to 1.27mm (0.05in)deflection.

14.1.3 The plate loading test is carried out in situ and it is difficult to ensure that thedensity and moisture content of the soils are appropriate to the post-constructionconditions17. It is best to do this test on a section prepared to the appropriatedensity (e.g. during compaction trials).

14.2 THE CALIFORNIA BEARING RATIO (CBR)

14.2.1 The strength of the subgrade for the design of flexible pavements is measured interms of the California Bearing Ratio (CBR) of the soil. The CBR test comparesthe force required to drive a plunger into the test material to a set penetration ata given rate, with the force required to cause the same penetration in a standardcrushed limestone. A full description of the test is given in BS 1377: Part 4,section 7. CBR tests may also be carried out in the field during the investigationstage (In situ), which is more desirable for soils of coarse granular nature andglacial tills.

14.2.2 The laboratory CBR test shall be carried out at a range of densities, which shallcover the range to be achieved during the construction and for each density, at arange of moisture contents ±15% of the design optimum moisture content. Thisgives a series of curves of CBR against moisture content from which a valueapplicable to the required construction/design condition can be obtained. It shouldbe noted that the soils resistance to penetration measured by the CBR test isdependent on the soil type and soil suction level. The soil suction potential cangreatly effect the CBR value, when tests are carried out on materials with moisturecontents of less than the Plastic Limit91. For high moisture contents or low soilsuction levels the CBR test will show low values, rapidly increasing in value withthe further reduction in the moisture content, until the soil approaches theshrinkage limit or wilting point of vegetation (see appendix D).

14.2.3 In conditions where it is difficult to choose a design moisture content due tovariable ground water conditions, the test can be done on 4-day soaked samples in

27

order to give a reasonably conservative value 19,20. These conditions could include:

Subgrade where there is a considerable variation of moisture content withdepth, in an otherwise homogenous soil. This is likely when the water tablelies near to or within the depth of soil being considered.Areas where there is a large annual variation in moisture content due to afluctuating water table, or possibly a spring thaw.

14.2.4 Laboratory tests on granular materials can give unrealistically high results becauseof the confining effect of the test mould. In situ tests may give lower figures butare often inappropriate because of the difficulty in testing at the relevant densityand moisture content. The British Soil Classification System can be used as aguide to selecting a design CBR value. This Standard also recommends amaximum design value of CBR should be restricted to 30% for unboundconstructions.

14.2.5 Selecting a representative design CBR value can be difficult if the CBR variesconsiderably with depth. There is no problem if the CBR increases with depth asthe critical value is the lowest one, i.e. at the formation. If the CBR decreaseswith depth (eg. a layer of sand or gravel overlying a clay), designing on a highCBR value representative of the top layer could overstress the weaker underlyinglayer, but designing for the CBR of the lower layer will lead to an uneconomicpavement. In this situation Figs 3 and 4 can be used to obtain an equivalent CBRfor the two layer system.

14.3 COMPACTION OF SUBGRADE

14.3.1 The compaction of subgrade to a uniform profile and at a consistent density andshear strength should be achieved to provide a formation for the subsequentconstruction of the pavement layers. Compaction of the subgrade will increase itsdensity and shear strength characteristics and prevent excessive settlements undertraffic which may otherwise lead to the premature failure of the pavement.Preparation of the subgrade may only require trimming and rolling (compaction),however, it is frequently necessary to dig-out (remove) localised soft spots andreduce the water content.

14.3.2 Control of settlement due to repetitive loading by traffic is achieved by obtainingspecific relative compaction levels in the subgrade. (See Table 12). As thesubgrade under a rigid pavement is less highly stressed than under a flexible one,the relative compaction requirements are less stringent under rigid pavements21,22,23.

14.3.3 If the relative compaction required cannot be achieved for the natural subgradematerials, the subgrade may be either treated by chemical mixing, see subsection15.3 or should be removed and replaced with suitable (preferably granular) fill oroverlaid with an additional layer of suitable fill referred to as either sub-base orbase material. The aim is that the un-compacted subgrade should be at a depthbeneath the formation where the in situ relative compaction is equal to or greaterthan that required. This additional material can be taken as enhancing thesubgrade, as long as the relative compactions still comply with those required at

i)

ii)

28

the new subgrade strength.

14.3.4 The amount of compaction possible in a soil will largely depend on the naturaldensity and moisture content, but certain soils raise particular problems.

These are:High and Medium plasticity clays;Silts and very fine sands with a moisture content at or approachingsaturation level;Uniformly graded non-cohesive materials.

14.3.5 High plasticity and some medium plasticity clays (see the revised British StandardSoil Classification) are liable to show a serious decrease in strength whencompacted at high moisture contents, especially when over-consolidated. In theUK the natural moisture content of these soils is normally well above the optimumfor heavy compaction so their undisturbed densities and strengths can rarely beimproved by further compaction. In their undisturbed state, these soils giverelative compactions ranging from 85-92% and CBR's ranging from 2-5% attypical moisture contents. From Table 12, these relative compactions are similarto or slightly lower than those required immediately under the pavement.However, experience in the UK has shown that rigid pavements with lean concretebases constructed on medium and high plasticity clays provide good long-termperformance without excessive settlement. It is recommended that constructionshall cause the least possible disturbance when constructing on these soils. Onceexposed, the subgrade shall be covered with the next construction layer as soon aspossible to protect it from the weather and to provide a working platform area forfurther construction operations.

29

i)ii)

iii)

TABLE 12 - Relative Compaction Requirements for Subgrade

Pavement Type

Rigid incorporatinga strong cement-bound base

Rigid withoutstrong cement-bound base

Flexible

Fill/Embankment Areas

Cohesive

90%

90%

The top 225 mm - 95%The remainder - 90%

Non-Cohesive

95%



Cut Areas

Cohesive

The top 150mmIf k >40-90%If k <40-85%

The top 150mmI f k >40-85%Ifk <40-80%

Ref58

Non-Cohesive

The top 600 mmIf k >50-95%If k <50-90%

The top 150 mmIf k >50-98%If k <50-95%Between 150 mmand 600 mmIf k >50-95%If k <50-90%

Ref58

Notes to Table 12 (table revised from reference 58)

For the purpose of determining relative compaction requirements non-cohesive soils arethose for which the fraction passing 425 micron sieve size has a plasticity index (PI) of lessthan 6.The density requirements are expressed as a percentage of the maximum dry density givenby BS 1377: Part JestSee Section on Weak Subgrade if CBR value less than CBR 2%.Subgrade which cannot realistically be compacted to the requirements in Table 12, shouldbe removed and replaced with fill or overlaid with additional depth of fill, sub-base or basematerial. This additional depth of construction should be sufficient to ensure that therequirements for relative compaction with depth beneath the pavement are achieved.

14.3.6 In dry climatical conditions the compaction of high plasticity and some mediumplasticity soils can present different problems (see also subsection 15.4). In thedry season these soils will generally have a natural moisture content well below theoptimum for heavy compaction, and thus if too highly compacted they are likelyto swell in a later wet season. But if compacted at too high a moisture content,a low dry density will be achieved and the soil is likely to shrink during a dryperiod. Special care is therefore needed to achieve a moisture content and degreeof compaction which reduces subsequent swelling or shrinkage to acceptable levels.In general the appropriate moisture content for compaction will be just above theoptimum moisture content. Chemical treatment of the soils by mixing the top layerwith either cement, bitumen or lime can frequently help reduce long termmovements within the subgrade (see subsection 15.3).

14.3.7 Silts and very fine sands with moisture contents at or approaching saturation levelcannot be compacted. If it is not practical to drain these areas or remove andbackfill them, the pavement design should be based on a very poor subgradestrength which reflects a saturated condition. With the pavement designs beingbased on a low CBR the density requirement is unlikely to be critical. To reduce

30

(i)

(ii)

(iii)(iv)

the effect of poor and variable subgrade support a flexible or a rigid pavementdesign may incorporate a lean concrete base, or the formations (subgrade) may betreated by chemical stabilisation.

14.3.8 It is difficult to achieve compaction of uniformly graded non-cohesive materials.One method of overcoming this is to compact through a thin layer (75-100mm) ofa well-graded material or capping layer. This layer will have no significant effecton the subgrade strength (CBR or k), which should be taken as that of thecompacted underlying material.

15.0 DESIGN GUIDANCE

15.1 SUBSOIL AND SUBGRADE DRAINAGE

15.1.1 This standard that has already indicated the strength of the subsoil may be greatlyaffected by the influence of excessive moisture content, high groundwater table,artesian pressures, springs and issues. Protection of the subgrade by drainage istherefore highly recommended and desirable for several reasons:

To increase subgrade strength by reducing the moisture content of the soilsTo reduce the chances of the moisture content increasing above thatassumed in the selection of a design subgrade strength.To drain the formation and pavement layers during construction.To drain any unpaved shoulders after construction.To drain granular layers in an unbound pavement structure afterconstruction. In this case the drainage is more likely to be essential ratherthan desirable as explained in paragraph 15.1.5.

15.1.2 There are a number of reasons for changes in the moisture content of subgrade,including:

Seepage flow from higher ground adjacent to the pavement.Changes in the water table level.Transfer of moisture to and from soil adjacent to the pavement.Percolation of moisture through the pavement.

15.1.3 Maximum benefit can be obtained from subsoil drainage if it is designed to reducethe moisture content of the soils prior to and during construction (e.g. by stoppingseepage flow or lowering the water table). After construction the drainage shouldwork to maintain the moisture content at or below that achieved duringconstruction (e.g. by continuing to stop seepage flow, by preventing a rise in thewater table or by removing water entering through the pavement or from theadjacent soil).

15.1.4 It is possible to drain the formation and pavement layers during construction byshaping and by protecting the formation and installing subsoil drains beforeconstruction starts.

ii)iii)iv)

i)ii)

iii)iv)v)

31

15.1.5 The large width of runways and other airfield pavements often make it uneconomicto lower or control the water table because the shape of the drawdown curve wouldrequire drains to be installed at impracticable depths. In this case the pavementshould be designed for a high water table. However, it is important that the watertable is kept at least 300mm below granular pavement layers to prevent thembecoming saturated and to minimise the pumping of fines into the layers byrepetitive aircraft loading. A geotextile fabric can also be used as a separator tocontrol the latter problem72. Ideally the same control of the water table levelshould be applied to other pavements to prevent undue deterioration of theirmaterials. If necessary, the formation should be elevated to raise the pavement farenough above the highest likely water table.

15.1.6 In assessing whether to install subsoil drainage, careful consideration should begiven to the economic gains from potential benefits as compared to the cost of thesystem. Factors to be considered include the actual effectiveness of the systemwhich will partly depend on the permeability of the soil, the availability of aconvenient outfall and the problems of installing drainage before the mainconstruction starts.

15.2 VERY WEAK SUBGRADE (EXCEPT PEAT)

15.2.1 Very weak subgrade may be considered to have CBR values of less than 3% or amodulus of subgrade reaction of less than 20 MN/m2/m and generally include highplasticity clays and silts either saturated or nearly saturated. The support to thepavement provided by these soils is non-uniform. In the long-term theperformance of the pavements will therefore be unpredictable and likely to besubject to premature localised failure.

15.2.2 Wherever practical these soils should be removed and backfilled with suitable fillmaterial. As a lesser alternative sub section 15.3, sets out a procedure forimproving subgrade support by overlaying with suitable fill material.

15.3 SUBGRADE IMPROVEMENT

15.3.1 On poor subgrade an economic option may be to use suitable fill material whichis available locally to improve the effective subgrade support to the pavement andthereby reduce the thickness of pavement required. The use of geotextiles72

incorporated within fill layers may increase stability of the fill, increasing the shearstrength and providing a more uniform support to the pavement. A thick layer offill will provide a more uniform support to the pavement, although high plasticityclays may suffer long term consolidation and loss of pavement shape.

15.4 EXPANSIVE SOILS

15.4.1 Some soils can show large volume changes when the moisture content changes.This can lead to loss of uniform support to the pavement, a reduction of bearingcapacity of the soil, and bumps, hollows and cracks in the pavement. Generallythe problem is only severe in climates where a long hot dry period is followed bya rainy season; the subgrade dries and shrinks during the hot season, but then

32

expands rapidly as the rainy season increases the moisture content. As anapproximate guide, the Plasticity Index gives a good indication of the expansivenature of a soil; values less than 20 are non-expansive nature of a soil; between20 and 40 are moderately expansive; and above 40 can be highly expansive. Fora more accurate assessment a technique related to the shrinkage limit and expectedrange of moisture content is described in Reference 18 and 59. Problems can alsooccur if an expansive soil is compacted in too dry a condition or allowed to dry outduring construction.

15.4.2 The effect of expansive soils can be much reduced by careful control of moisturecontent during construction and the degree of compaction achieved, (see paragraph14.3). If future expansion is still likely to be excessive, soil swell can be limitedby, for example, providing sufficient fill/overburden.

15.4.3 The support to pavements may be improved by the use of chemical stabilisationincreasing the soils strength by mechanical mixing (generally only 5 % by volume)with cement or lime this technique can generate tenfold increases in the strengthof the materials. Careful consideration must be given to the fluctuations and levelsof the groundwater table. Highly plastic soils may have their plastic behaviourreduced by the addition of lime, whereas volcanic soils frequently benefit fromcement or lime additions. For less plastic soils bitumen stabilisation may givebetter results. Special consideration should be given to soils of the andosol group,which generally have a loosely cemented soil fabric that quickly collapses whenused as fill and dried out.

15.5 FROST SUSCEPTIBILITY

15.5.1 For the United Kingdom and similar temperate climates, material placed within450mm of the surface of the pavement may be subject to freezing. Hence in areaswhere frost susceptible soils will lie immediately below the formation a minimumof 450mm of pavement construction shall be provided irrespective of all otherconsiderations.

15.5.2 Tests for frost susceptibility have been carried out by TRRL on a variety ofmaterials used as subgrade, sub-bases and bases both in research and duringroutine testing for motorway and trunk road project.s Test results and otheraspects of frost susceptibility are contained in TRRL Report No LR9025 . TheFrost Test method described in LR90 has been superseded by that in aSupplementary Report 82926 and BS 812, Part 124.

15.5.3 Soils which commonly exhibit a tendency to be frost susceptible include:

Cohesive soils with plasticity index less than 15% (well drained soils) or20% (poorly drained soils - within 600mm of the water table)crushed chalkBurnt colliery shaleLimestone gravels with aggregate saturation moisture content greater than2 percent.Hard limestones with more than 2% aggregate saturation moisture content.

33

Oolite and Magnesium Limestones with more than 3 % aggregate saturationmoisture content.Pulverised fuel ash with more than 40% passing a 200 micron sieve.

15.6 PEAT

15.6.1 Subgrades of peat are highly compressible and have very little bearing capacity.Pavements constructed on them can suffer from serious differential settlement, sopeat should usually be removed and replaced with a suitable fill. A possible optionis to surcharge the peat with fill to reduce the short term consolidationsubstantially. But this may make a long and phased construction necessary and inthe long term the performance of the pavement will be less certain; there may belocalised failures and general loss of shape. This alternative should not be usedfor pavements whose longitudinal and transverse profiles are critical; eg. runwaysand major taxiways. Consider it, however, for stopways73.

15.7 SPRING THAW AND PERMAFROST

15.7.1 In certain parts of the world where frost conditions are severe, pavements must bedesigned for the effects of spring thaw and permafrost. Both the spring thaw andintermittent or partial melting of a permafrost layer can considerably reduce thesubgrade's bearing capacity which reduces the load-carrying capacity of thepavement74.

15.8 CONSTRUCTION PRACTICE

15.8.1 Experience has shown that if the moisture content of the subgrade is allowed toincrease during construction the final equilibrium strength will be lower than if ithad not. It is therefore important that the specification requirements for protectingthe formation are complied with, or the design CBR value should be reducedaccordingly.

15.8.2 Construction traffic can damage or reduce the natural strength of the subgrade.The use of the formation in areas of cut should be restricted to the minimum plantand equipment essential for the overlying construction. For subgrade particularlyprone to damage (e.g. high plasticity clays and silts) a working course of dry leanconcrete or granular sub-base/capping layer should be placed on the subgradebefore construction continues. In fill areas construction traffic should be restrictedto prevent damage to compacted layers and the subgrade. To allow reshaping andrecompaction, rut depths in granular layers should not exceed about 40 mm.24

16.0 AGGREGATE FOR THE CONSTRUCTION OF PAVEMENTS

16.1 Aggregates are the basic material for pavement construction, and are preparedfrom natural rock or from granular sedimentary deposits (Gravels).

16.2 The properties of gravels depend upon the parent rock constituent materials andcrystalline structure.

34

16.3 The use of aggregates in either flexible or rigid pavements design calls for a rangeof different characteristics. The tests will allow prediction of the "inservice"performance and will enable materials from different sources to be compared.

16.3 Table 13 Aggregate testing summarises the recommended tests for pavementconstruction.

TABLE 13 - List of Recommended Aggregate Testing

TestDescription

Physical Tests

Grading Curves (PSD)

Shape Index

Density

Water Absorption

Petrographic Examination

Mechanical Tests

Impact Value (AIV)

Crashing Value (ACV)

Ten Percent Fines Value

Franklin Point Load Test

Schmidt Rebound Number

Durabililty Tests

Abrasion Value (Aabv)

Attrition

Los Angeles Abrasion Value

Polished Stone Value

Slake Durability Value

Sulphate Content

Sulphate Soundness


Chemical Tests

Chloride Test

Sulphate Test

Organic Content

RecommendedStandard for Test

Statistical Number required forconfidence Limits

Low Medium High

BS 812:Part 103and BS 882

BS 812:Part 105

BS 812

BS 812

BRE Digest 35(ASTM C295)

1-3

3

2

3

5

6

6

5

6

10

9

9

8

9

15

BS 812:Part 112

BS 812:Part 110

BS 812:Part 111

Franklin (1970)

Duncan (1969)

3-6

3-6

3-6

3-6

3-6

8

8

8

8

8

12

12

12

12

12

BS 812:Part 113

BS 812

ASTM-C131

BS 812:Part 114

Franklin (1970)Rock Characterisation

Testing and Monitoring,ISRM

BS 812:Part 121(Magnesium)ASTM - C88

(Sodium)

BS 812:Part 124

BS 812:Part 117

BS 812:Part 118


3

3

3

3

3

2

3

3

3

3

6

6

6

6

6

6

9

9

9

9

12

12

12

12

12

12

18

18

18

18

35

Adhesion TRRL 1962 3 9 18

REFERENCES

Air Ministry Works Department. Design and Construction of Concrete Pavements. Air Publication No AP 3129A. 1945.

Air Ministry Works Department. Load Classification of Runways and Aircraft. Technical Publication 102. 1948.

Air Ministry Works Department. Airfield Evaluation. Technical Publication 104. 1952.

Air Ministry Works Department. The Fundamentals of Airfield Pavement Design. Technical Publication 107. 1953.

Air Ministry Works Department. Airfield Design and Evaluation. Technical Publication 109. 1959.

JL Dawson and RL Mills. Undercarriage Effects on (a) Rigid Pavements (b) Flexible Pavements. ICE Proceedings ofSymposium on Aircraft Pavement Design. 1970.

FR Martin, AR Macrae. Current British pavement Design. ICE Proceedings of Symposium on Aircraft Pavement Design.1970.

H Jennings, FLH Straw. Strengthening of pavements. ICE Proceedings of Symposium on Aircraft Pavement Design. 1970.

Department of the Environment. Design and Evaluation of Aircraft Pavements 1971.

International Civil Aviation Organisation. Aerodrome Design Manual Parts 1-3, First Edition 1977, Second Edition 1983.

Bums et al. Multiple Heavy Wheel Gear Load Pavement Tests; Design, Construction and Behaviour under Traffic.Technical Report S-71-17, Vol II, Nov 1971, US Army Engineer Waterways Experiment Station.

Barns et al. Comparative Performance of Structural Layers in Pavement Systems. FAA Report No FAA-RD-73-198,volume I,II,III.

US Army Engineer Waterways Experiment Station. Procedures for Development of CBR Design Curves-Instruction ReportS-77-1. 1977.

International Civil Aviation Organisation. Annex 14. Aerodromes-International Standards and Recommended Practices.Eigth Edition. 1983.

Civil Aviation Authority. United Kingdom Aeronautical Information Publication. London. 1982.

British Standards Institution. Methods of Tests for Soils for Civil Engineering Purposes. BS1377: 1990, Parts 1 to 9.

Road Research laboratory. Soil Mechanics for Road Engineers. HMSO. 1952.

D Croney. The Design and Performance of Road Pavements. HMSO. London. 1977.

US Army Engineer Waterways Experiment Station. Field Moisture Content Investigation, October 1945-November 1952Phase. Report No 2. 1955.

US Army Engineer Waterways Experiment Station. Field Moisture Content Investigation, November 1952-May 1956 Phase.Report No.3. 1961.

WA Lewis. Full Scale Compaction Studies at the British Road Research Laboratory. Highways Research Board Bulletin254. Washington. 1960.

US Army Engineer Waterways Experiment Station. Compaction Requirements for Soil Components of Flexible AirfieldPavements. Technical Report No 3-529. 1959.

WJ Tumbull and Charles R Foster. Proof Rolling of Subgrade. Highway Research Borad Bulletin 254. Washington.1960.

WD Powell, JF Potter, HC Mayhew and ME Nunn. The Structural Design of Bituminous Roads. Report LR 1132.Transport and Road Research Laboratory, Crowthome, Berks. 1984.

D Croney and JC Jacobs. The Frost Susceptibility of Soils and Road Materials. RRL Report LR 90. Transport and RoadResearch Laboratory, Crowthorne, Berks. 1967.

PG Roe and DC Webster. Specification for the TRRL Frost Heave Test, Supplementary Report 829. Transport and RoadResearch Laboratory, Crowthorne, Berks. 1984.

RG Packard. Fatigue Concepts for Concrete Aircraft Pavement Design. Transportation Engineering Journal. 1974.

A Guide to the Testing of Airfield Pavements using the PSA Plate Bearing Test. Property Services Agency DCES AirfieldsBranch. 1984.

17.0

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

RL Hutchingson. Basis for Rigid Pavement Designs for Military Airfields. Miscellaneous Paper No 5-7. US Army Corpsof Engineers, Ohio River Institute. Washington DC. 19S8.

US Army Corps of Engineers Waterways Experiment Station. Validation of Soil Strength Criteria for Aircraft Operationson Unprepared Landing Strips. Technical Report No 3-554. July 1960.

Military Engineering Experimental Establishment. Sinkage of a Dual Aircraft Wheel Assembly. Report No 925.Christchurch October 1965.

DN Brown and OO Thompson. Lateral Distribution of Aircraft Traffic. Miscellaneous Paper S-73056 July 1973. US ArmyEngineer Waterways Experimental Station, Vicksburg. 1973.

HM Westergaard. Stresses in Concrete Pavements Computed by Theoretical Analysis. Public Roads. Vol 7 No2. 1926.

G Pickett, ME Raville, WC Jones, FJ McCormick. Deflections, Movements and Reactive Pressures for Concretepavements. Kansas State College Bulletin 65. October 1951.

RG Packard. Computer Programme for Airport Pavement Design. Portland Cement Association. Chicago, Illinois. 1967.

G Pickett. Concrete Pavement Design, Appendix HI: A Study of Stresses in the Comer Region of Concrete PavementSlabs under Large Comer Loads. Portland Cement Association, Skorkie. 1946.

US Army Corps of Engineers. Final Report on the Dynamic Loading of Concrete Test Slabs - Wright Field Slab Tests.Ohio River Division Laboratories, Mariemont, Ohio. August 1943.

R H Ledbetter. Pavement response to Aircraft Dynamic Loads. FAA Report No FAA-RD-74-39-m. June 1973.

Highway Research Board. Joint Spacing in Concrete Pavements: 10 year Reports on Six Experimental Projects. ResearchReport 17-B. 1956.

BE Colley and HA Humphrey. Aggregate Interlock in Joints in Concrete Pavements. Highway Research Record Number189. 1967.

LD Childs. Effect of Granular and Soil-Cement Sub-bases on Load Capacity of Concrete Slabs. Journal of the PCAResearch and Development Laboratories, Vol 2, No 2. 1960.

LD Childs and JW Kaperick. Tests of Concrete Pavement Slabs on Gravel Sub-bases. Proceedings ASCE, Vol 84 (HW3).October 1958.

LD Childs. Tests of Concrete Pavement Slabs on Cement Treated Sub-bases. Highway Research Record 60, HighwayResearch Board. 1964.

LD Childs. Cement Treated Sub-bases for Concrete Pavements. Highway Research Record 1989, Highway ResearchBoard. 1967.

Air Ministry Works Department. Investigation into the Value of Lean Concrete as a Base in Rigid Pavements. Air MinistryTech Memo No 4. 1955.

RD Bradbury. Reinforced Concrete Pavements. Wire Reinforcement Institute. Washington DC. 1938.

LW Teller and EC Sutherland. The Structural Design of Concrete Pavements. Public Roads Vol 16, No 8,9 and 10, 1935;Vol 17 No 7 and 8, 1936; and Vol 23, No 8, 1943.

J Thomlinson. Temperature Variations and Consequent Stresses Produced by Daily and Seasonal Temperature Cycles inConcrete Slabs. Road Research Laboratory. June 1940.

US Army Corps of Engineers. Lockbourne No. 1 Test Track. Final Report. Ohio River Division Laboratories, Mariemont,Ohio. March 1946.

Charles R Foster and R G Ahlvin. Notes on the Corps of Engineers CBR Design Procedures. Highways Research BoardBulletin 210, Washington, 1959.

FR Martin. A Heavy-Duty Airfield pavement Embodying Soil Stabilisation. ICE. Airport Paper 34.

MA Napier. A Report on the Testing of Stabilised Soil Airfield Pavements 1955-60. MEXE Report No 592.

British Standards Institution, "Code of Practice for Site Investigation", BS 5930: 1981.

British Standards Institution "Code of Practice for Earthworks", BS 6031: 1981.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.

RL Hutchingson. Basis for Rigid Pavement Designs for Military Airfields. Miscellaneous Paper No 5-7. US Army Corpsof Engineers, Ohio River Institute. Washington DC. 1958.

US Army Corps of Engineers Waterways Experiment Station. Validation of Soil Strength Criteria for Aircraft Operationson Unprepared Landing Strips. Technical Report No 3-554. July 1960.

Military Engineering Experimental Establishment. Sinkage of a Dual Aircraft Wheel Assembly. Report No 925.Christchurch October 1965.

DN Brown and OO Thompson. Lateral Distribution of Aircraft Traffic. Miscellaneous Paper S-73056 July 1973. US ArmyEngineer Waterways Experimental Station, Vicksburg. 1973.

HM Westergaard. Stresses in Concrete Pavements Computed by Theoretical Analysis. Public Roads. Vol 7 No 2. 1926.

G Pickett, ME Raville, WC Jones, FJ McCormick. Deflections, Movements and Reactive Pressures for Concretepavements. Kansas State College Bulletin 65. October 1951.

RG Packard. Computer Programme for Airport Pavement Design. Portland Cement Association. Chicago, Illinois. 1967.

G Pickett. Concrete Pavement Design, Appendix HI: A Study of Stresses in the Corner Region of Concrete PavementSlabs under Large Comer Loads. Portland Cement Association, Skorkie. 1946.

US Army Corps of Engineers. Final Report on the Dynamic Loading of Concrete Test Slabs - Wright Field Slab Tests.Ohio River Division Laboratories, Mariemont, Ohio. August 1943.

R H Ledbetter. Pavement response to Aircraft Dynamic Loads. FAA Report No FAA-RD-74-39-III. June 1973.

Highway Research Board. Joint Spacing in Concrete Pavements: 10 year Reports on Six Experimental Projects. ResearchReport 17-B. 1956.

BE Colley and HA Humphrey. Aggregate Interlock in Joints in Concrete Pavements. Highway Research Record Number189. 1967.

LD Childs. Effect of Granular and Soil-Cement Sub-bases on Load Capacity of Concrete Slabs. Journal of the PCAResearch and Development Laboratories, Vol 2, No 2. 1960.

LD Childs and JW Kaperick. Tests of Concrete Pavement Slabs on Gravel Sub-bases. Proceedings ASCE, Vol 84 (HW3).October 1958.

LD Childs. Tests of Concrete Pavement Slabs on Cement Treated Sub-bases. Highway Research Record 60, HighwayResearch Board. 1964.

LD Childs. Cement Treated Sub-bases for Concrete Pavements. Highway Research Record 1989, Highway ResearchBoard. 1967.

Air Ministry Works Department. Investigation into the Value of Lean Concrete as a Base in Rigid Pavements. Air MinistryTech Memo No 4. 1955.

RD Bradbury. Reinforced Concrete Pavements. Wire Reinforcement Institute. Washington DC. 1938.

LW Teller and EC Sutherland. The Structural Design of Concrete Pavements. Public Roads Vol 16, No 8,9 and 10, 1935;Vol 17 No 7 and 8, 1936; and Vol 23, No 8, 1943.

J Thomlinson. Temperature Variations and Consequent Stresses Produced by Daily and Seasonal Temperature Cycles inConcrete Slabs. Road Research Laboratory. June 1940.

US Army Corps of Engineers. Lockbourne No. 1 Test Track. Final Report. Ohio River Division Laboratories, Mariemont,Ohio. March 1946.

Charles R Foster and R G Ahlvin. Notes on the Corps of Engineers CBR Design Procedures. Highways Research BoardBulletin 210, Washington, 1959.

FR Martin. A Heavy-Duty Airfield pavement Embodying Soil Stabilisation. ICE. Airport Paper 34.

MA Napier. A Report on the Testing of Stabilised Soil Airfield Pavements 1955-60. MEXE Report No 592.

British Standards Institution, "Code of Practice for Site Investigation", BS 5930: 1981.

British Standards Institution "Code of Practice for Earthworks", BS 6031: 1981.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.

Institution of Civil Engineers. Site Investigation Steering Group. Site Investigation in Construction (1993)Volume 1 - Without Site Investigation Ground is a HazardVolume 2 - Planning Procurement and Quality ManagementVolume 3 - Specification for Ground InvestigationVolume 4 - Guidelines for the Safe Investigation of Drilling of Landfills and Contaminated Land

CIRIA (Weltman AJ and Mead JM). Site Investigation Manual. Special Publication 25 PSA Civil Engineering TechnicalGuide 35, 1983.

British Standards Institution, Draft of Code of Practice for the Identification of Potentially Contaminated Land and itsInvestigation, DD175: 1988.

Property Services Agency, A Guide to Airfield Pavement Design and Evolution, 1989.

Geological Society Engineering Group Working Party Report, Tropical Residual Soils, Quarterly Journal of EngineeringGeology, 1990, Volume 23, No.l.

Federal Aviation Administration, Washington, USA, Advisory Circular 150/5320-6C, Airfield Pavement Design andEvaluation, 1978.

AC Meigh, Cone Penetration Testing, Methods and Interpretation, CIRIA, Ground Engineering Report: In-situ Testing,1987.

N Ashford and PH Wright, Airport Engineering, J Wiley and Sons, 1979.

MP O'Reilly and RS Millard, Roadmaking Materials and Pavement Design in Tropical and Sub-tropical Countries, LLReport LR 279, Transport and Road Research Laboratory, 1969.

Association of Geotechnical Specialists. The Electronic Transfer of Geotechnical Data from Ground Investigations (1992).

British Drilling Association. Guidance Notes for the Safe Drilling of Landfills and Contaminated Land (1992).

Proceedings of the Geotechnology Conference organised by the Institution of Civil Engineers, Penetration testing in the UK,Thomas Telford, 1988.

CIRIA Report No. 131 (1993). The Measurement of Methane and other Gases from the Ground, D Crowhurst and SJManchester.

Geological Society Engineering Geology Special Publication No.9, Aggregates, 1993.

British Standards Institute, Quality Systems, 1987

British Standards Institute, Code of Practice for Safety Precautions in the Construction of Large Diameter Boreholes forPiling and other Purposes, 1978

IK Nixon, The Standard Penetration Test - A State-of-the-Art Report, Proc. European Symp. on Penetration Testing n,Amsterdam, 1982, Vol 1, 3 to 24.

R Veldhuijzen Van Zanten, Geotextiles and Geomembranes in Civil Engineering, AA Balkema, Rotterdam, 1986

GP Raymond, Design of Embankments on Peat, Analysis and Design in Geotechnical Engineering Vol I, 1974, Universityof Texas, American Society of Civil Eng. - Geotech. End. Div.

FG Bell, Ground Engineer's Reference Book, 1987, Butterworth.

Department of Transport, Specification and Method of Measurement for Ground Investigation, 1987.

ICRCL 59/83 Guidance on the Assessment and Redevelopment of contaminated land, 2nd Edition 1987.

PT Sherwood, Soil Stabilisation with Cement and Lime, State of the Art Report, HMSO, 1993

The Influence of Trees on House Foundations, BRE Digest 298, 1987

A Method of Determining the State of Dessiccation in Soils, BRE IP4/93, 1993

WD Powell, JF Potter,HC Mathew and ME Nunn, The Structual Design of Bituminous Roads, TRRL LR1132, 1984

M J Dumbleton, G West, Air photograph interpretation for road engineers in Britain., TRRL LR369, 1970

Working Party Report: Land Surface Evaluation for Engineering Purposes, Quat. Journal of Eng. Geol., vol 15, No 4

CIRIA Ground Engineering Report: In-situ Testing, Cone Penetration Testing Methods and Interpretation, A.C Meigh, 1987

55.

56.

57.

58.

59.

60.

61.

62.

63.

64.

65.

66.

67.

68.

69.

70.

71.

72.

73.

74.

75.

76.

77.

78.

79.

80

81

82

83

Working Party Report: The Description of rock masses for engineering purposes, Quat. Journal of Eng. Geol., vol 10, No 4

N Wright, Assessment of Road Surface Hardness, TRRL SR573, 1980

Working Party Report: The Logging of rock cores for Engineering Purposes, Quat. Journal of Eng. Geol., vol 3, No 1

A Sorensen, M Hayven, The Dynatest 8000 Falling Weight Deflectometer Test System, Int. Sym. on Bearing Capacity ofRoads and Airfields, Proceedings, Trondheim, 1982

PJ Norman, RA Snowdon, JC Jacobs, Pavement Deflection Measurements and their Application to Structural Maintenanceand Overlay Design, TRRL LR571, 1973

Department of Transport, Advise Note HA 25/83, Deflection Measurement of Flexible Pavements. Analysis, Interpretationand Application of Deflection Measurements, DOT, 1983

CIRIA Ground Engineering Report: In-situ Testing, Pressuremeter Testing methods and interpretation, Butterworths, 1987

SF Brown, MP O'Reilly, The relationship between California Bearing Ratio and Elastic Stiffness for Compacted Clays,Ground Engineering, October, 1990

AAB Williams, JT Pidgeon, Evapotranspiration and heaving clays in South Africa, Geotechnique, vol 33, pp 93-105

MJ Dumbleton, G West, Soil Suction by Rapid Method: An apparatus with extended range, Journ. of Soil Science, Vol 19,No 1, pp 40-46

84

85

86

87

88

89

90

91

92

93

FIGURES

Appendix A Extended Casagrande Soil Classificationand CBR/k Relationship

TABLE A1 - The Extended Casagrande Soil Classification

TABLE A2 - Extended Soil Classification with Material Characteristics

Note: The use of this classification system is described in section 9.

Figure 2 - California Bearing Ratio verses Modulus of Subgrade Reaction

Note: The size of plate used in the correlation was 762 mm (30 inches) diameter.

Thickness of granular sub-base (mm)

Effect of granular sub-base onthe modulus of subgrade reaction

(k) for rigid pavements

Tab

le A

1 E

xten

ded

Cas

agra

nde

clas

sific

atio

n

Table A2 - Extended Soils Classification with Material Characteristics

160

140

120

100 80 60 40 20

320

25

30

CB

R/k

Rel

atio

nshi

p

350

12

Log

Li

near

CB

R (

%)

604

510

1540

4550

55

Appendix B Standard Cone Penetrometer Charts

Identification of soils using the Dutch mechanical friction sleeve penefromefer(from

Identification of soils using the reference test penetrometer tip (R) .(a) Full scheme (after Douglas and(b) Working version (after Roberfson and Campanella, 1983).

Appendix C Interpretation of Pavement VisualSurvey Data

OBSERVATION INTERPRETATION

Single longitudinalwheelpath cracks inbituminous surface

Multiple wheelpathcracking and crazing inbituminous surface

Indicates the onset of structural failure in a thick (> 200mm approx)pavement or one with a cement bound base. If cracks are narrow, thenthis probably represents the 'critical condition of the pavement. Such cracks do notnormally 'heal in any way and deterioration is likely to progress.

If cracks are narrow as defined in Table 3.2 then the structure is likely to be thinand the condition may not be near failure. Wider cracks mean advanced failure ofa thicker structure, particularly if rutting is also present.

Longitudinal crackingoutside the wheelpath inbituminous surface

Probably the location of a construction joint in one of the pavement layers.

Short transverse cracks Unlikely to be structurally significant. Cracking has probably initiated at the surface,in bituminous surface possibly due to faults built in during construction, e.g. roller cracks. Such cracks

will develop slowly under thermal and traffic loading, and may allow longitudinalcracks to develop.

Long transverse cracksin bituminous surface

Indicative of a discontinuity in a lower layer. This can be a thermal crack in acement bound roadbase, a joint in an overlaid concrete carriageway or a constructionjoint in bituminous material.

In the case of cement bound roadbase, the frequency and severity of transversecracking gives an indication of the state of the material. Widely spaced cracks aretypical of a strong or newly laid material. The following is a guide to interpretingcrack frequency:-

Interpretation of Visual Survey Data

Similarly, the amount of cracking is indicative of the traffic carried, as follows: -

Non Structural (narrow) ruts

Structural (wide) ruts

The upper layers, probably the wearing course, are deforming(rather than simply densifying) under traffic. No effect on lowerlayers will usually result.

Deformation is taking place at depth within the pavement.Significant ruts indicate structural damage, possibly due to excessmoisture in unbound materials and/or overstressing of thesubgrade.

Represents either the onset of structural failure, differentialsettlement, or compression at joints. Deterioration is likely to berapid but sealing and stitching of cracks can reduce the crackpropagation rate. Such cracking tends to occur in underdesigned(thin) pavements.

Mid bay/third by cracks in concretepavements

Joint damage in concrete pavements

Thermally induced cracks in URCpavements, a consequence of joint malfunction. They can, if leftunsealed, result in more serious distress. If sealed, then littledetriment to the pavement may result. In JRC pavements, wherecracks are expected and act as warping joints, sealing is onlynecessary if the cracks are wide.

Spalling, sealant damage, stepping etc. are all indications that thereis excess movement at the joint. Load transfer is probably poor;damage to the foundations and possibly voiding may have occurred.

Interpretation of Visual Survey Data

Longitudinal cracks in concrete pavements

WEA

THER

TEM

PER

ATU

RE

VIS

UA

L C

ON

DIT

ION

SU

RV

EY O

F

STA

RT

NO

DE

010

2030

4050

Run

ning

Cha

inag

e(m

)

TOTA

L L

ENG

TH S

UR

VEY

EDK

m

OF BY

SHEE

T N

OD

ATE

VIS

UA

L C

ON

DIT

ION

SU

RV

EYS

SEC

TIO

N I

DEN

TIFI

ERFI

NIS

H N

OD

E

0 5

Off

set

(m)

10 15

Appendix D CBR versus Soil Suction Curve and SoilDesiccation Potential

Determination of potential expansiveness of soils

(after Van der Merwe, D.H., The prediction of

heave from the plasticity index and percentage

clay fraction of soils'. The Civil Engr in S. Afr.,

S. Afr. Inst. Civil Engrs., 6, 103-16 (1964).

Moisture content-suction relationships for

Onderstepoort. Vereeniging and Welkom clays

(from Williams and Pidgeon).

USAEWES classification of swell potential (from O'Neill and Poormoayed)

Liquid limit

(%)

Less than 50

50-60

Over 60

Plastic limit

(%)

Less than 25

25-35

Over 35

Initial (in situ)

suction (kPa)

Less than 145

145-385

Over 385

Potential swell

(%)

Less than 0.5

0.5-1.5

Over 1.5

Classification

Low

Marginal

High

Printed in the United Kingdom for HMSODd298008 8/94 C6 G3397 10170

Defence Works Functional Standards 09 - UK · PDF fileDefence Works Functional Standards 09 ... 10 Ground Investigation and Field Testing ... 6.3 Flexible pavement design shall be

Documents