FOR INTERNAL CIRCULATION ONLY user’s manual of Construction Soil Investigation & Foundations Construction Management Power Grid Corporation of India Limited (A Government of India Enterprise) DOCUMENT CODE NO. : CM/TL/SOIL INVESTIGATION & FOUNDATIONS/FINAL/98 OCT, 1998
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FOR INTERNAL CIRCULATION ONLY
user’s manual of Construction
Soil Investigation&
Foundations
Construction ManagementPower Grid Corporation of India Limited
It gives me immense pleasure to learn that Construction Management has come out with
further four volumes of User’s Manual of Construction : ‘Soil Investigation & Foundations’,
‘Pile & Well Foundations’, ‘Contracts Management’ and ‘Transformers & Reactors’.
The various changes in the wake of rapid advances in technologies and growing competition
on global basis has made it imperative to conceptualise the methods for optimizing our
resources; the 5M’s namely men, money, machines, materials and methods. They are the
basics to realize a construction project and time, cost & quality are its critical parameters.
The construction of transmission line is a wide canvas and complex in nature that needs a
multi disciplinary approach. However, no standard guidelines or manuals in consolidated
form are available for its various construction activities.
I compliment the Construction Management team for bringing out these manuals wherein
the main focus of the authors has been to combine the theoretical & practical aspects drawn
from their respective experience in transmission lines construction, academic institutions
and industry. An attempt has been made to explain the fundamentals in a simple & lucid
language. I am convinced that these manuals will act as guidelines and serve the needs of
our practicing Managers & site Engineers.
I should be our endeavour to follow these systems and procedures to enhance the quality of
construction management in transmission and quality power. More such User’s Manuals
covering the other related fields should be prepared for the benefit of the ultimate users at
our remote sites as well as for the younger generation inducted in POWERGRID.
(R.P. SINGH)
CONTENTS
SECTION-I
SOIL INVESTIGATION
SL. NO. DESCRIPTION PAGE NO.1.0 INTRODUCTION 11.1 PURPOSE OF SOIL INVESTIGATION 11.2 TYPE OF TESTING 31.2.1 BORING 31.2.2 SHELL AND AUGER BORING 31.3 SAMPLING 41.3.1 GENERAL 41.3.2 DISTURBED SAMPLE 41.3.3 UNDISTURBED SAMPLE 51.3.4 UNDISTURBED SAMPLING IN COHESIVE SOIL 61.3.5 UNDISTURBED SAMPLING USING PISTON SAMPLER 61.3.6 UNDISTURBED SAMPLING IN COHESIONLESS SOILS 71.3.7 TYPES OF SAMPLERS 71.4 INSITU PERMEABILITY TEST 71.4.1 PUMP-IN TEST 81.5 STANDARD PENETRATION TEST 91.6 STATIC CONE PENETRATION TEST 111.7 DYNAMIC CONE PENETRATION TEST 121.8 VANE SHEAR TEST 121.9 PLATE LOAD TEST 132.0 TRIAL PIT 152.1 GROUND WATER 182.2 ELECTRICAL RESISTIVITY TEST 192.3 FIELD INVESTIGATION ROCK 202.4 LABORATORY TESTING 242.5 REPORT 292.6 RATES & MEASUREMENTS 372.7 SPECIFIC REQUIREMENTS FOR GEOTECHNICAL
INVESTIGATION AT RIVER CROSSINGS
39
2.8 SUMMARY OF RESULTS OF LABORATORY TEST ON
SOIL AND WATER SAMPLES
40
2.9 TOOLS AND PLANTS FOR SOIL INVESTIGATIONS 423.0 GUIDELINES FOR CONDUCTING SOIL INVESTIGATION
IN TRANSMISSION LINE
44
SECTION-II
TOWER FOUNDATIONS
CHAPTER-1
GENERAL
SL. NO. DESCRIPTION PAGE NO.1.0 TOWER FOUNDATIONS1.1 LOADS, SAFETY FACTORS AND SETTLEMENT1.2 CLASSIFICATION OF SOILS1.3 PROPERTIES OF SOILS1.4 DATA FOR FOUNDATION DESIGN
CHAPTER-2
TYPES OF FOUNDATIONS
SL. NO. DESCRIPTION PAGE NO.2.0 INTRODUCTION2.1 TYPES OF FOUNDATION
CHAPTER-3
CLASSIFICATION AND STUB SETTING
SL. NO. DESCRIPTION PAGE NO.3.0 LINE CONSTRUCTION3.1 INVESTIGATION AND SURVEY3.2 TRANSPORTATION3.3 FOUNDATION3.4 PREPARATION OF FOUNDATION SITE3.5 TYPE OF FOUNDATION TO BE ADOPTED3.6 PIT MARKING3.7 SHORING AND SHUTTERING3.8 DEWATERING3.9 EXCAVATION IN ROCK3.10 PROCEDURE FOR SETTING STUBS OF SITE BY
COMBINED STUB SETTING
CHAPTER-4
TYPES OF FOUNDATIONS
SL. NO. DESCRIPTION PAGE NO.4.0 CONCRETE TYPE4.1 MIXES4.2 SIZES OF AGGREGATES4.3 GRAVEL SUB-BASE4.4 REINFORCEMENT4.5 FORM WORK4.6 MIXING, PLACING AND COMPACTING OF CONCRETE4.7 BACK FILLING4.8 CURING
CHAPTER-5
PROTECTION OF FOUNDATION
SL. NO. DESCRIPTION PAGE NO.5.0 CONCRETE TYPE5.1 UPLIFT RESISTANCE
5.2 REVETMENT5.3 BENCHING5.4 PROTECTION OF FOUNDATION AGAINST CHEMICAL
WATER5.5 MEASUREMENT OF VOLUME FOR REVETMENT AND
BENCHING
CHAPTER-6
CONCRETE TECHNOLOGY
SL. NO. DESCRIPTION PAGE NO.6.1 INTRODUCTION6.2 PROPORTIONING CONCRETE MIXTURES6.3 FRESH CONCRETE6.4 HANDING AND BATCHING CONCRETE MATERIALS6.5 BATCH PLANTS AND MIXERS6.6 READY MIXED CONCRETE6.7 MOVING AND PLACING CONCRETE6.8 CONSOLIDATING CONCRETE6.9 RECOMMENDED VIBRATION PRACTICES6.10 FINISHING AND CURING CONCRETE6.11 PLACING CONCRETE IN COLD WEATHER6.12 PLACING CONCRETE IN HOT WEATHER
CHAPTER-7
MECHANISED CONSTRUCTION
SL. NO. DESCRIPTION PAGE NO.7.0 INTRODUCTION7.1 MECHANICAL CONSTRUCTION EQUIPMENT & THEIR
APPLICATIONS7.2 WORK STUDY ON CONSTRUCTION EQUIPMENT7.3 PLANT PURCHASE VERSUS PLANT HIRE7.4 SAFETY PROGRAMME7.5 WHY MECHANICAL CONSTRUCTION EQUIPMENT?7.6 PRODUCTION OUT PUTS7.7 PRODUCTION TRIAL7.8 ECONOMIC LIFE
CHAPTER-8
STANDARD FIELD QUALITY PLAN
SL. NO. DESCRIPTION PAGE NO.
8.0 STANDARD FIELD QUALITY PLAN FOR TRANSMISSION
LINE PACKAGES
CHAPTER-9
GUIDELINES
SL. NO. DESCRIPTION PAGE NO.9.0 PIT MARKING9.1 STUB SETTING9.2 CONSTRUCTION MATERIALS9.3 INSTALLATION OF REINFORCEMENT STEEL & FORM
BOXES9.4 MIXING, PLACING AND COMPACTING OF CONCRETE
CHAPTER-10
CHECK FORMAT
SL. NO. DESCRIPTION PAGE NO.1.0 CHECK FORMAT FOR PIT MARKING2.0 CHECK FORMAT FOR FOUNDATION CLASSIFICATION3.0 CHECK FORMAT FOR STUB SETTING4.0 CHECK FORMAT FOR CONSTRUCTION MATERIALS5.0 CHECK FORMAT FOR INSTALLATION OF
REINFORCEMENT STEEL & FORM BOXES6.0 CHECK FORMAT FOR MIXING, PLACING AND
COMPACTING OF CONCRETEANNEXURE-IA : TOOLS & PLANTS FOR EXCAVATION,
STUB SETTING AND CONCRETINGANNEXURE-IB : MANPOWER FOR EXCAVATION, STUB
An investigation of sill is essential for judging its suitability for the proposed
engineering works and for preparing adequate and economic design. In
general, the purpose of soil investigation is to obtain necessary information
about the soil and to know the engineering properties of soil which will be
affected.
Earlier, the soil investigation of locations of transmission line towers was not
very popular and general practice had been to adopt 4to 5 types of standard
design foundations for different classes of soils encountered. Only special
foundations in river beds necessitating huge volumes of concrete were
investigated for properties of soils. Now the soil investigation of normal
foundations is also felt necessary in good number of locations in the 400 kv
transmission lines which helps in better choice of standard foundation &
development of new designs to achieve overall cost, economy and minimise
chances of failure.
1.1 Purpose of soil investigation:
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a) Technical Consideration
b) Economic Consideration
a) Technical Considerations : An inadequate design or a conservative
choice of standard foundation can lead to a failure causing long outage
of transmission line. In modern practice, a large variety of standardised
foundations are being pre-designed with different sets of properties
attached to forseeably encountered soils. Aarge varity of soils are
encountered as length of transmission lines are increasing with voltage
llevels going up. To obtain optimal choice of pre-designed standard
foundations,it is very much necessary to have a proper scientific
knowledgfe of properties of soil against the back-drop of increasing
sizes of towers, foundations, loads, thereby minimising the risk of fail-
ures of foundations.
b) Economic Considerations : Among site erection activities, the
foundations form the major chunk of the cost. The cost of foundations
constitures 50 to 70% of the toral cost of erection depending upon
terrain conditions. It forms 10 to 15% of the total cost of transmission
line. A considerable saving in the foundation cost can be achieved by
having detailed knowledge of soil properties and making wide usage of
them in designing the foundations in sufficient types and classification
of the foundations in field to match the most optimum size and type of
foundation.
1.2 Types of Testing :
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1.2.1 Boring : Bore holes are generally taken at specified locations to obtain
information about the sub soil profile, its nature and strength and to collect soil
samples for strata identification and conducting laboratory tests. The minimum
diameter of the bore hole shall be 150 mm and boring shall be carried out in
accordance with the provision of IS:1892. Casing pipe is used in the bore hole
to support its side when a side fall is suspected to occur inside the borehole.
When casing pipe is used, it shall be ensured that its bottom end is at all times
less than 15cms above the bottom of the borehole and not below the level at
which the test has to be conducted or sampling has to be done. In case of
cohesion less soils the advancement of the casing pipe shall be such that it
does not disturb the soil to be tested or sampled. The casing shall be advanced
by slowly turning the casing pipe and not by driving.
1.2.2 Shell and Auger Boring: Cylindrical augers and shells with cutting edge on
teeth at the lower end can be used for making deep boring. Hand operated
rings are used for depths up to about 25m and the mechanized rings up to 50m.
Shell and auger boring can be used in all types of soil free from boulders. For
cohesion less soil below ground water table, the water table in the borehole
shall always be maintained at or above the ground water level. The use of
chisel bit is permitted in hard strate with SPT-N value greater than 100.Chisel
bits are also used to extend the borehole through local obstructions such as old
construction boulders, rocky formation etc. The various activities to be
conducted during the boring include standard penetration test, collection of
undisturbed and disturbed samples of soil at various depths, logging of
different layers of soil, depth of subsoil water and preparation of data sheets.
Further a series of tests have to be conducted on the disturbed and undisturbed
samples of soil at laboratory.
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1.3 Sampling :
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1.3.1 General :
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(a) Sufficient number of soil samples shall be collected. Disturbed soil
samples shall be collected for field identification and conducting tests
such as sieve analysis, index properties, specific gravity, chemical
analysis etc. Undisturbed sample shall be collected to estimate the
physical strength and settlement properties of the soil. All the
accessories required for sampling and the method of sampling shall
confirm to IS:2132.
(b) All the samples shall be identified with date, bore hole and trial pit
number, depth f sampling etc. It is also essential to mark and arrow
pointing towards the top surface of the sample as the soil was in-situ.
Care shall be taken to keep the core samples and box samples vertically
with the arrow directing upwards . The tube samples shall be properly
trimmed at one end and suitably caped and sealed with molten paraffin
wax.
1.3.2 Disturbed Sample
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a) Disturbed soil samples shall be collected in bore holes at regular
itervals.Jar samples weighing approximately 10N shall be collected in
boreholes at 0.5m intervals starting from a depth of 0.5 m below ground
level and at every identifiable change of strata to supplement the boring
records. Samples shall be immediately stored in air tight jars and shall fill
the jar as far as possible.
b) In elevated areas, if superficial material is available in plenty, then bulk
samples from a depth of about 0.5m below ground level shall be
collected to establish all the required properties to use it as a fill
material. Disturbed samples weighing about 250 N shall be collected at
shallow depths and immediately stored in polythene bags as per
IS:1892. The bags shall be sealed properly to avoid any change in
moisture content and they shall be kept in wooden boxes.
1.3.3 Undisturbed Sample :
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In each borehole undisturbed sample shall be collected at every change of
strata and depths of 1.0 4.0 7.0,10.013.0,15.5m and water at regular intervals
of 3.0m and as directed by the Engineer. The depth interval between the top
levels of undisturbed sampling and standard penetration test shall not be less
than 10.m. Undisturbed samples shall be of 100m dia and 450 mm length.
Samples shall be collected in such a manner that the structure of the soil and
its moisture content do not get asserted. The specifications for the accessories
required for sampling and the sampling procedure shall conform to IS:1892
and IS:2132. Undisturbed sampling in sand shall be done using compressed air
technique mentioned in IS:8763. Thin walled sampler shall be used to collect
undisturbed samples by pushing the tube into the soil. The sampling tube shall
have a smooth finish on both surfaces and minimum effective length of
450mm. The area ratio of sampling tubes shall be less than 12.5%. However,
in case of very stiff soils, area ratio up to 20% shall be permitted. Area ratio
should be as low as possible. In no case it should be greater than 25%. The
inside clearance of the sampler should lie between 1 to 3 percent and the
outside clearance should not be much greater than the inside clearance.
1.3.4 Undisturbed Sampling in Cohesive Soil
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Undisturbed samples in soft to stiff cohesive soils shall be obtained using a
thin walled sampler. In order to reduce the wall friction, suitable precautions
such as oiling the surfaces shall be taken.
1.3.5 Undisturbed Sampling using Piston Sampler
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Undisturbed samples in very loose saturated sandy and silty soils and very soft
clays shall be obtained by using a piston system. In soft clays and silty clays,
with water standing in the casing pipe, piston sampler shall be used to collect
undisturbed samples. During this method of sampling expert supervision is
called for. Accurate measurement of the depth of sampling, height of sampler,
stroke and length of sample recovery shall be recorded. After the sampler is
pushed to the required depth, both the sampler cylinder and piston system shall
be drawn up together ensuring that there shall not be any disturbance to the
sample which shall then be protected from changes in moisture content.
1.3.6 Undisturbed Sampling in Cohesion less Soils
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Undisturbed samples in cohesionless soils shall be obtained as per the
procedure given in IS:8763. Compressed air sampler shall be used to take
samples of cohesionless soils below water table.
1.3.7 Type of Samplers:
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Samplers which shall be used commonly at sites are open drive sampler,
stationary piston sampler, and Rotary samplers depending upon the mode of
operation. Open drive types can be both the thick and thin wall samplers and
the stationary piston and the rotary types are thin wall sampler - depending
upon the area ratio (Fig.1 & Fig.2)
D22 - D12
Area ratio = ------------------- X 100 Percent D12
D3 - D1Inside Clearance = ---------------- X 100 percent
D1
D2 - D4
Outside Clearance = ---------------- X 100 percent
D4
1.4 In situ permeability test : In situ permeability test shall be conducted to
determine the water percolation capacity of overburden soil. The specification
for the equipments required for the test and the procedure of testing shall be in
accordance with IS: 5529, part -1. When it is required to carry out the
permeability test for a particular section of the soil strata above the ground
water table, bentonite slurry shall not be used while boring.
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1.4.1 Pump-in test:
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Pump-in test shall be conducted in the bore hole/trial pit by allowing water to
percolate into the soil. Choice of the method of testing shall depend on the soil
permeability and prevailing ground water level.
a) Constant Head Method ( in bore hole):
This test shall be conducted in boreholes where soils have a high
permeability i.e. it shall be allowed into the borehole through a
metering system ensuring gravity flow at constant head so as to
maintain a steady water level in the borehole. A reference mark shall
be made at a convenient level which can be easily seen in the casing
pipe to note down the fluctuations of water level. The fluctuation shall
be counteracted by varying the quantity of water flowing into the
borehole. The elevation of water shall be observed at every 5 minute
interval. When three consecutive readings show constant value, the
necessary observations such as flow rate, elevation of water surface
above test depth, diameter of casing pipe etc. Shall be made and
recorded as per the proforma recommended in IS:5529, PART-I,
Appendix-A.
b) Falling head method ( in bore hole)
This method shall ve adopted for relatively less permeable soils where
the discharge is small and where the soil can stand without casing. The
test section shall be seated by the bottom of the borehole and a packer
at the top of the test section. If the test has to be conducted at an
intermediate section of a prebored hole then, double packer shall be
used . Access to the test section through the packer shall be by means
of a pipe which shall extend to above the ground level. Water shall be
filled into the pipe upto the level marked just below the top of the pipe
and water allowed to drain into the test section. The water level in the
pipe shall be recorded at regular intervals as mentioned in
IS:5229,part-I, Appendix- B. The test shall be repeated till constant
records of water level are achieved.
1.5 Standard penetration Test :
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The test shall be performed in a clean hole, 55 to 150 mm in diameter. A
casing or drilling mud shall be used to support the sides of the hole. The test
shall be conducted at depth of 2.0, 3.0, 5.0, 6.0, 8.0, 9.0, 11.0, 12.0, 14.0, m
and at 3.0m intervals and every change of strata and as per the direction of the
Engineer-in-charge. A standard thick wall split-tube sampler, 50.8 mm shall be
driven into the undisturbed soil at the bottom of the hole under the blows of a
65 kg drive weight with 75 cm free fall. The minimum open length of the
sampler should be 60 cm. The sampler shall be first driven through 15 cm as a
seating drive. It shall be further driven through 30cm or until 100 blows are
applied. The number of blows required to give the sampler 30 cm beyond the
seating drive, is termed as penetration resistance N. This test shall be
discontinued when the blow count is equal to 100 or the penetration is less
than2.5 cm for 50 blows whichever is earlier. At the location were the test is
discontinued the penetration and the number of blows shall be reported.
Sufficient quantity of disturbed soil samples shall be collected from the split
spoon sampler for identification and laboratory testing.
Following Tables give some of the empirical correlation of the soil properties
with the penetration resistance corrected for depth and for fine saturated sand.
Table (1) Penetraqtion resistance and Empirical correlations for cohesionless soils.
PenetrationResistance N
(Blows)
Approx.
(Degrees)
DensityIndex(%)
Description Approx.Moist
Density(t/m2)
-
4
10
30
50
25-30
27-32
30-35
35-40
38-43
0
15
35
65
85
Very Loose
Loose
Medium
Dense
Very dense
1.12-1.6
1.44-1.84
1.76 –2.08
1.76 –2.24
2.08 –2.40
Table (2) : Penetration resistance and empirical correlations for cohesive soils
PenetrationResistanceN (blows)
UnconfinedCompressive
Strength (t/m2)
SaturatedDensity(t/m3)
Consistency
0
2
4
8
16
32
0
2.5
5
10
20
40
-
1.6 - 1.92
1.76 -2.08
-
1.92 - 2.24
-
Very soft
Soft
Medium
Stiff
Very stiff
Hard
1.6 Static cone penetration test : Static cone penetration test shall be conducted
to know the soil stratification and to estimate the various soil propertie such
as density, undrained shear strength etc. The cone penetrometer shall be
advanced by pushing and the static forcr required for unit penetration shall be
determined. The test shall be conducted upto the specified depth or refusal
whichever is earlier. For this test ‘refusal’ means meeting a very hard strata
which can’t be penetrated at the rate of at least 0.3cm/sec even when the
equipment is loaded to its full capacity. The specifications for the equipment
and accessories required for performing the test, test procedure, field
observations and reporting of results shall conform to 1S: 4968, Part 111. Only
100 kN capacity mechanically operated equipment shall be used. At the
ground level, preboring upto 0.5 m depth shall be permitted if the overlying
strata is hard. Continuous record of the penetration resistance shall be
maintained.
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1.7 Dynamic cone penetration test: Dynamic cone penetration test shall be conducted to
predict stratification, density, bearing capacity etc of soils. The test shall be conducted
upto the specified depth or refusal whichever is earlier. Refusal shall be considered when
the blow count exceeds 150 for 300mm penetration. The specification for the equipment
and accessories re- quired for performing this test, test procedure, field observations and
reporting of results shall conform to 18:4968 Part-ll. The driving system shall comprise
of a 650 weight having a free fall of 0.75m. The cone shall be of 65 mm diameter
provided with vents for'continuous flow of bentonite slurry through the cone and rods in
order to avoid friction between the rods & soil. On completion of the test, the result shall
be presented as a continuous record of the number of blows required for every 300mm
penetration of the cone into the soil in a suitable chart supplemented by a graphical plot
of blow count for 300 mm penetration vs. depth.
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1.8 Vane shear test: Field vane shear test shall be performed inside the borehole
to determine the undrained shear strength of cohesive soil -especially of soft
and sensitive clays, which are highly susceptible to sampling disturbance. The
vane shear test consist of four thin steel plates called vanes, welded
orthogonally to a steel rod (Fig.3) .The test shall be conducted by advancing
this four winged vane of s~itable size (as per the soil condition) into the soil
upto the desired depth and measuring the torque required to rotate the vane.
The torque shall be measured through a torque measuring arrangements such
as calibrated torsion spring, is attached to the steel rod which is rotated by a
worm gear and worm wheel arrangement. The specification for the equipments
and accessories required for conducting the test, the test procedure and field
observations shall correspond to IS: 4434. Tests mayalso be conducted by
direct penetration from ground surface. On completion of the test the results
shall be reported in an approved proforma as specified in IS: 4434, Appendix-
A.
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1.9 Plate Load Test: Plate load test shall be conducted to determine the ultimate
bearing capacity of soil, and the load/settlement characteristics of soil at
shallow depths by loading a plane and leveled steel plate kept at the desired
depth and measuring the settlement under different loads, until a desired
settlement takes place or failure occurs. The specification for the equipment
and accessories required for conducting the test, the test procedure, field
observations and reporting of results shall conform to IS:1888. The test pit
shall be made five times the width of the plate. At the centre of the pit, a small
square hole shall be dug whose size shall be equal to the size of the plate and
the bottom level of which correspond to the level of actual foundation (Fig.4) .
The loading to the test plate shall be applied with the help of a hydraulic jack.
The reaction of the hydraulic jack shall be borne by either of the following two
methods:
a) Gravity loading platform method
b) Reaction truss method.
In case of gravity loading method a platform shall be constructed over a
vertical column resting on the test plate and the loading shall be done with the
help of sand bags, stones or concrete blocks. The general arrangement of the
set up for this method is shown in Fig. 5 & 6.
If the water table is at a depth higher than the specified test depth, the
groundwater shall be lowered and maintained at the test depth for the entire
duration of the test.
1.9.1 A seating load of 70 gm/sq.cm shall be applied and after the dial gauge
readings are stabilized , the load shall be released and the initial readings of
the dial gauges recorded after they indicate constant reading. The load shall be
increased in stages. These stages shall be 20, 40, 70, 100, 150, 200, 250, 300,
400, 500, 600 and 800 KN per sq.m. or as directed by the Engineer. Under
each loading stage, record of Time vs Settlement shall be kept as specified in
IS: 1888.
The load shall be maintained for a minimum duration of one hour or till the
settlement rate reduces to 0.02 mm/ min whichever is later. No extrapolation
of settlement rate from periods less than one hour shall be permitted.
1.9.2 Loading shall be carried out in stages as specified above till one of the
following conditions occurs.
a) Failure of the soil under the plate i.e. the settlement of the plate at
constant load becomes progressive and reaches a value of 40 mm or
more.
b) Total settlement of the plate is more than 40 mm.
c) Load intensity of 800 KN/Sq.m is reached without failure of the soil.
1.9.3 Dial gauge readings for settlement shall generally be taken at
1,2.25,4,6.25,9,16,25,60,90 and 120 minutes from the commencement of each stage
of loading. Thereafter the readings shall be taken at hourly intervals upto a further 4
hours and at two hours intervals thereafter for another 6 hours .
2.0 Trial pit
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2.0.1 Trial pits shall be of minimum 2mx2m size at the bottom so as to permit easy access
for visual examination of walls of the pit and to facilitate sampling and insitu testing
operations. pits shall be upto 4 m deep or as per the directions of the Engineer.
Precautions shall be taken to ensure the stability of pit walls including provision of
shoring, if necessary, as per IS: 4453: Precautions shall be taken to prevent surface
water draining into the pit. Arrangements shall be made for dewatering if the pit is
extended below water table. Trial pits shall be kept dry and a ladder shall be provided
for easy access to the bottom of the pit. In-situ tests shall be conducted and
undisturbed samples shall be collected immediately on reaching the specified depth so
as to avoid substantial changes in moisture content of the subsoil. Arrangements shall
be made for barriers, protective measures and lighting necessary for the period the pits
remain open.
2.0.2 A note on the visual examination of soil strata shall be prepared. This should include
the nature, colour, consistency and visual classification of the soil, thickness of soil
strata, groundwater table, if any, etc.
2.0.3 Undisturbed samples shall be collected at 1.0, 2.0, 3.0 m depth and at the termination
depth in all the pits.
a) Chunk Samples
In cohesive soils, undisturbed samples of regular shapes shall be
collected. The samples shall be cut and trimmed to a suitable size
(0.3x0.3x0.3m). A square area (0.35x0.35m) shall be marked at the
centre of the leveled surface at the bottom of the pit. Without
disturbing the soil inside the marked area, the soil around this marking
shall be carefully removed upto a depth of 0.3Sm. The four vertical
faces of the soil block protruding at the centre to be trimmed slowly so
that its size reduces to 0.3mx0.3m. Wax paper cut to suitable size shall
be wrapped uniformly covered with two layers of thin cloth over all the
S exposed surfaces of the soil block and sealed properly using molten
wax. A firmly constructed wooden box of size 0.3Sx0.35x0.35m
(internal dimensions) with the top and bottom open shall be placed
around the soil block and held such that its top edge protrudes just
above the surface of the block. The space between the soil block and
the box shall be filled uniformly and tightly with moist sawdust. The
top surface shall also be covered with saw dust before nailing the
wooden lid to cover the box firmly taking care that the soil block is not
disturbed. The area of contact between the bottom portion of the block
and the ground shall be reduced slowly by removing soil in small
quantities using small rods, so that the block can be separated from the
ground slowly without disturbance. After inverting the wooden box
along with the soil block, the bottom portion shall be trimmed and
covered with wax paper, cloth and sealed with molten wax. A wooden
lid shall be nailed to the box after providing proper saw dust cushion
below it. An arrow mark shall be made on the vertical face of the
wooden box to indicate the top surface along wi th the coordinates and
depth of sampling .
b) Tube Samples
Undisturbed tube samples may also be obtained by means of a l00mm
diameter sampling tube with a cutting edge. The sampler shall be
slightly oiled or greased inside and outside to reduce friction. The
sampler shall be pushed into the soil and while doing so, soil around
the tube shall be carefully removed. In case it is not possible to push
the sample, it may be driven by light blows from a "monkey".
2.0.4 In each trial pit the soil in-situ density shall be determined by the sand
replacement method. The specifications, equipments, accessories required for
the test and test procedure shall be as per IS: 2720, Part- XXVIII. No separate
payment shall be made for this test.
2.1 Ground Water
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2.1.1 One of the following methods shall be adopted for determining the ground water table
in bore holes as per IS: 693 5 and as per the lnstructions of the Engineer.
a) In permeable soils, the water level in the hole shall be allowed to
stablise after depressing it adequately by bailing. When the water level
inside the bore hole is found to be stable, the depth of water level
below ground level shall be measured. Stability of sides and bottom of
the bore hole shall be ensured at all times.
b) For both permeable and impermeable soils, the [following method
shall be suitable. The bore hole shall be filled with water and then
bailed out to various depths. Observations on the rise or fall of water
level shall be made at each depth. The level at which neither a fall nor
a rise is observed shall be considered as the water table elevation. This
shall be established by three successive readings of water level taken at
an interval of two hours.
2.1.2 In case any variation in the groundwater level is observed in any specific boreholes,
then the water level in these I boreholes shall be recorded daily during the course of
the field investigation. Levels in nearby wells, streams, etc., if any, shall also be noted
whenever these readings are taken.
2.1.3 Sub-soil Water Samples
a) Sub-soil water samples shall be collected for carrying out chemical
analysis thereon. Representative samples of groundwater shall be
collected when it is first encountered in bore holes before the addition
of water to aid boring or drilling.
b) Chemical analysis of water samples shall include determination of pH
value; turbidity, sulphate, carbonate, nitrate and chloride contents;
presence of organic matter and suspended solids. Chemical
preservatives maybe added to the sample for cases as specified in'the
test method/IS codes. This shall only be done if analysis cannot be
conducted within an hour of collection and shall have the prior written
permission and approval of the Engineer.
2.2 Electrical Resistivity Test
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This test shall be conducted to determine the Electrical resistivity of soil
required for designing safety grounding system for the entire switch yard area.
The specifications for the equipments and other accessories required for
performing electrical resistivity test, the test procedure, and reporting of field
observations shall conform to 1S:3043. The test shall be conducted using
Wanner's four electrode method as specified in 1S:1892,Appendix-
B2.Unlessotherwisespecified, at each test location, the test shall be conducted
along two perpendicular lines parallel to the coordinate axes. On each line a
minimum of 8 to 10 readings shall be taken by changing the spacing of the
electrodes from an initial small value of 0.5m upto a distance of 10.0m.
2.3 Field Investigation Rock
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2.3.1 Rock Drilling
a) Boring shall be continued in large hard fragments or natural rock beds
like but not limited to igneous, sedimentary and metamorphic
formations. The equipments, method and the procedure for drilling
operation shall conform to IS:1892. The starting depth of drilling in
rock shall be certified by the Engineer. The portion drilled in rock shall
be backfilled with cement and sand (1:3) grout.
b) Drilling shall be carried out with NX size tungston carbide (TC) or
diamond tipped drill bits depending on the type of rock and as per
IS:6926. Suitable type of drill bit (TC/Diamond) and core catchers
shall be used to ensure continuous and good core recovery. Core
barrels and core catchers shall be used for breaking off the core and
retaining i t when the rods are withdrawn. Double tube core barrels
shall be used to ensure better core recovery and to pick up cores from
layers of bed rock. Water shall be circulated continuously down the
hollow rods and the sludge conveying the rock cuttings to the surface
shall be collected. A very high recovery ratio shall be aimed at in order
to get a satisfactory undisturbed sample. Core of minimum 1.5m length
shall be aimed at. Normally TC bit shall be used. Change over to a
diamond bit shall require the specific written approval of the Engineer
and his decision whether a TC or a diamond bit is to be used shall be
final and binding on the Contractor.
c) No drilling run shall exceed 1.5m in length. If the core recovery is less
than 80% in any run the length of the subsequent run shall be reduced
to 0.75m. During drilling operations observations on return water, rate
of penetration, etc., shall be made and recorded as per IS:5313.
i) The colour of return water at regular intervals, the depth at
which any change of colour of return water is observed, the
depth of occurrence and amount of flow of hot water, if
encountered, shall be recorded.
ii) The depth through which a uniform rate of penetration was
maintained, the depth at which marked change in rate of
penetration or sudden fall of drill rod occurs the depth at which
any blockage of drill bit causing core loss, if any, shall be
recorded.
iii) Any heavy vibration or torque noticed during drilling should be
recorded together with the depth of occurrence.
iv) Special conditions like the depth at which grouting was done
during drilling fluid, observation of gas discharge with return
water etc., shall also be observed and recorded.
v) All the observations and other details shall be recorded as a
daily drill and reported in a proforma as given in IS:5313.
d) Core samples shall be extracted by the application of a continuous
pressure at one end of the core with the barrel held horizontally without
vibration. Friable cores shall be extracted from the barrel directly into
a suitable sized half round plastic channel section. Care shall be taken
to maintain the direction of extrusion of sample same as while coring
to avoid stress reversal.
e) Immediately after withdrawl from the core barrel, the cores shall be
placed in a tray and transferred to boxes specially prepared for the
purpose. The boxes shall be made from seasoned timber or any other
durable material and shall be indexed on top of the lid as per IS : 4078.
The cores shall be numbered serially and arranged in the boxes in a
sequential order. The description of the core samples shall be recorded
as per IS : 4464. Where no core is recovered, it shall be recorded as
specified in the standard. Continuous record of core recovery and RQD
to be mentioned in the corelog as per IS : 11315 Part-II.
2.3.2 Permeability Test
Permeability Test shall be conducted in bedrock inside the drilled holes by
pumping in water under pressure to determine the percolation capacity of the
rock strata. This test shall be conducted in uncased and ungrouted sections of
the drill hole and the use of bentonite slurry during drilling is strictly
prohibited when this test has to be conducted.
Clear and clean water shall be used for the purpose of both drilling and testing.
The equipments required and the procedure to be followed for conducting the
test shall conform to IS : 5529, Part-II. The length of the test section shall be
either 1.5m or 3.0 m as per field conditions and the directions of the Engineer.
The level of water table, if any, in the drill hole shall be recorded and the drill
hole shall be cleaned before beginning the test. Depending upon the depth of
the test section, single packer or double packer method shall be adopted. Care
shall be taken to see that all joints and connections are watertight during the
test.
a) Single Packer Method
This method shall be adopted when the bottom elevation of the test
section is the same as the bottom of the drill hole and where it is
considered necessary to know the permeability values during drilling
itself. This test shall be useful where the full length of the hoe cannot
stand uncased or ungrouted. The packer shall be fixed at the top level
of test section such that only the test section lies below the packer.
Water shall then be pumped through a pipe into the test section under a
particular pressure and maintaining it till a constant quantity of water
intake is observed. The amount of water percolating through the hole
shall be recorded at every 5 mm intervals. The test shall be repeated by
increasing the pressure at regular intervals upto a pressure limit as
specified in IS : 5529, Part-II. The details and observations during the
test shall be suitably recorded in a proforma recommended in IS : 5529,
Part-II, Appendix-B.
b) Double Packer Method
This method shall be used when the permeability of an isolated section
inside a drill hole has to be determined. Packers shall be fixed both at
the top and bottom of the test section such that their spacing is exactly
equal to the length of the test section.
2.4 Laboratory Testing
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2.4.1 Essential Requirements
a) Depending on the type of sub strata encountered, appropriate laboratory
tests shall be conducted on soil and rock samples collected in the field.
Laboratory tests shall be scheduled and performed by qualified and
experienced personnel who are thoroughly conversant with the work. Tests
indicated in the schedule of items shall be performed on soil, water and
rock samples as per relevant IS: codes. One copy of all the laboratory test
data records shall be submitted to the Powergrid progressively every week.
Laboratory tests shall be carried out concurrently with field investigation
since initial laboratory test results could be useful in planning the later
stages of fieldwork. A schedule of laboratory tests shall be established by
the Contractor to the satisfaction of the Engineer within one week of
completion of the first borehole.
b) Laboratory tests shall be conducted using approved apparatus comply
in with the requirements and specifications of/'Indian Standards or
other approved standards for this class of work. It shall be checked that
the apparatus are in good working condition before starting the
laboratory tests./Calibration of all the instruments and their accessories
shall be done carefully and precisely. The tests shall be conducted at an
approved laboratory.
c) All samples, whether undisturbed or disturbed, shall be extracted,
prepared and examined by competent personnel properly trained and
experienced in soil sampling, examination, testing and in using the
apparatus as per the specified standards.
d) Undisturbed soil samples retained in lines or seamless tube /samplers
shall be taken out without causing any disturbance to the samples using
suitably designed extruders just prior to actual testing. If the extruder is
horizontal, proper support shall be provided to prevent the sample from
breaking. For screw type extruders, the pushing head shall be free from
the screw shaft so that no torque is app11ed to the soil sample in
contact with the pushing head. For soft clay samples, the sample tube
shall be cut by mean of a high speed hacksaw to proper test length and
placed over the mould before pushing the sample into it with a suitable
piston.
e) While extracting a sample from a liner or tube, care shall be taken to
see that its direction of movement is the same as that during sampling
to avoid stress reversal.
2.4.2 Tests
Tests as indicated in this specification and as called for by the Engineer shall
be conducted. These tests shall include but not be limited to the following.
a) Tests on Undisturbed and Disturbed Samples
- Visual and Engineering Classification
- Sieve Analysis and Hydrometer Analysis
- Liquid, Plastic and Shrinkage Limits
- Specific Gravity
- Chemical Analysis
- Swell Pressure and Free Swell index determination
- Proctor Compaction test
- California Bearing Ratio
b) Tests on Undisturbed Samples
- Bulk Density and Moisture Content
- Relative Density (for sand)
- Unconfined Compression Test
- Box Shear Test (in case of sand)
- Triaxial Shear Tests: (depending on the type of soil and field
conditions on undisturbed or remoulded samples )
i) Unconsolidated undrained,
ii) Consolidated Undrained Test with the Measurement of Pore
Water Pressure.
iii) Consolidated Drained.
- Consolidation
c) Tests on Rock Samples
- Visual Classification
- Moisture Content, Porosity and Density Specific Gravity Hardness
- Slake durability
- Unconfined Compression test (both saturated and at insitu water
content ) -Point load strength index
- Deformability test (both saturated and dry, samples)
d) Chemical Analysis of Sub soil water
2.4.3 Salient Test Requirements
a) Remoulded soil specimen, whenever desired, shall be fully reworked at
field density and moisture content . For conducting CBR test and
triaxial test for dyke and road material the sample shall be remoulded
to 95% of standard proctor density.
b) Triaxial shear test shall be conducted on undisturbed soil samples,
saturated by the application of back pressure. Only if the water table is
at sufficient depth so that chances of its rising to the base of the footing
are meagre or nil, the triaxial tests shall be performed on specimens at
natural moisture content. Each test shall be carried out on a set of three
test specimens from one sample at cell pressures equal to 100, 200 and
300 KN/sq.m. or as required depending on the soil conditions .
c) Effective stress triaxial shear test could be either consolidated drained
or consolidated undrained with pore water pressure measurement. The
test shall be conducted at cell pressure of 100,200 and 300 KN/ sqm.
increased in stages of 50 KN/sqm. ensuring complete consolidation at
each stage.
d) Direct shear test shall be conducted on undisturbed soil samples. The
three normal vertical stresses for each test shall be l00, 200 and 300
KN/sq.m. or as required as per the soil conditions .
e) Consolidation test shall have loading stages of 10, 25,50,75,100,200,
400and800KN/Sq.m. Rebound curve shall be recorded for all the
samples by unloading the specimen at the in-situ stress of the
specimen. Additional rebound curves shall also be recorded whenever
desired by the Engineer.
f) Chemical analysis of sub-soil shall include determination of pH value;
carbonate, sulphate (both SO3andSO4) , chloride and nitrate contents;
organic matter; salinity and any other chemical harmful. to the
foundation material. The contents in soils shall be indicated as
percentage ( % ) .
g) Chemical analysis of sub-soil water sample shall include the determination
of the properties such as colour, odour, turbidity, pH value and specific
conductivity both at 25 deg.C and chemical contents such as Carborates,
Surphates(both SO3 and SO4), Chlorides, Nitratesm Organic matter and any
other chemical harmful to the founmdation material. The contents such as
Sulphates, etc. shall be indicted as ppm by weight.
h) The lab CBR test shall be performed on undisturbed and remoulded
sample for soaked and unsoaked condition.
2.5 Report
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2.5.1 General
a) On completion of all the field and laboratory work, the Contractor shall
submit a formal report containing Geological information of the region,
procedure adopted for investigation, field observations, summarised
test data, conclusion and recommendations. The report shall include
detailed borelogs, subsoil sections, field test results, laboratory
observations and test results both in tabular as well as graphical form,
practical and theoritical considerations for the interpretation of test
results, the supporting calculations for the conclusions drawn, etc.
Initially, the Contractor shall submit three copies of the report in draft
from for the Owner's review.
b) The Contractor's qualified Geotechnical engineer shall visit the Owners
Corporate office for a detailed discussion on the Owners comments on
his draft report. During the discussions, it shall be decided as to the
modifications that need to be done in the draft report. Thereafter the
Contractor shall incorporate in his report the agreed modifications and
after get ting the amended draft report approved, ten copies of the
detailed final report shall be submitted alongwith one set of
reproducibles of the graphs, tables, etc .
c) The detailed final report based on field observations, in-situ and
laboratory tests shall encompass theoretical as well as practical
considerations for foundations for different types of structures
envisaged in the area under investigation. The Contractor shall
acquaint himself about the type of structures, foundation loads and
other information required from the Engineer.
2.5.2 Data to be Furnished
The report shall also include but not be limited to the following :
a) A plot plan showing the locations and reduced levels of all field tests
e.g. boreholes, trial pits, static cone penetration tests, dynamic cone
penetration tests, plate load tests 1 etc. properly drawn to scale and
dimensioned with reference to the established grid lines.
b) A true cross section of all individual boreholes and trial pits with
reduced levels and coordinates shown in the classification and
thickness of individual stratum, position of ground water table, various
in-situ tests conducted and samples collected at different depths and
the rock stratum, if met with.
c) A set of longitudinal and transverse soil/rock profiles connecting
various boreholes in order to give a clear picture of the variation of the
subsoil strata as per IS:6065.
d) Geological information of the area such as geomorphology, geological
structure, lithology, stratigraphy and tectonics, core recovery and rock
quality designation, etc.
e) Past observations and historical data, if available, for the area or for
other areas with similar soil profile or with similar structures in the
surrounding areas.
f) Plot of Standard Penetration Test (N values both uncorrected and
corrected) with depth for identified areas.
g) Results of all laboratory tests summarised (i) for each sample (as per
Table-I) as well as (ii) for each layer along with all the relevant charts,
tables, graphs, figures, supporting calculations, conclusitions and
photographs of representative rock cores.
h) For all triaxial shear tests stress vs strain diagrams as well as Mohr’ s
circle envelopes shall be furnished. If back pressure is applied for
saturation, the magnitude of the same shall b~ indicated. The value of
modulus of elasticity, E shall be furnished for all tests alongwith
relevant calculations.
i) For all consolidation tests, the following curves shall be furnished :
e vs log p
e vs p and
Compression vs log t or
Compression vs square root of t (depending upon the shape of the plot
for proper determination of co-efficient of consolidation).
The point showing the initial condition (eo, po) of the soil shall be
marked on the curves.
j) The procedure adopted for calculating the compression index from the
field curve and settlement of soil strata shall be clearly specified. The time
required for 50% and 90% primary consolidation alongwith secondary
settlements, if significant, shall also be calculated.
k) For pressuremeter tests, the following curves shall be furnished :
Field pressure meter, creep and air calibration curves indicating Po' Pf
and Pi.
Corrected pressure meter and creep curves indicating Po, Pf', Pi
alongwith calculation for the corrections.
l) From the pressure-meter test results the values of cohesion, angle of
internal friction, pressuremeter modulus, shear modulus and coefficient
of subgrade reaction shall be furnished alongwith sample calculation.
Calculation for allowable bearing pressures and corresponding total
settlements, for shallow foundations and capacity calculation of piles in
various modes shall also be included.
2.5.3 Recommendations
Recommendations shall be given area wise duly considering the type of soil,
structure and foundation in the area. The recommendations shall include but
not be limited to the following :
a ) Type of foundations to .adopt for various structures, duly considering
the sub soil characteristics, water table, total settlements permissible
for structures and equipments. Minimum depth and width of
foundation shall also be recommended. The provision in relevant IS:
Codes indicated in clause 4.0 shall be considered.
b) For shallow foundations the following shall be indicated with
comprehensive supporting calculations.
i) Net safe allowable bearing pressure for isolated square footings
and continuous strip footings of sizes 2.0,3.0 and 4.0m at three
different founding depths of 1.0, 2. 0 and 4.0m below ground
level considering both shear failure and settlement criteria,
giving reasons for type of shear failure adopted in the
calculation.
ii) Net safe allowable bearing pressure for raft foundations of
widths greater than 6m at 2.0m , 3.0m and 4.0m below ground
level considering both shear failure and settlement criteria.
iii) rate and magnitude of settlement expected of the structure.
iv) Net safe bearing capacity for foundation sizes mentioned above,
modulus of subgrade reaction, modulus of elasticity from plate
load test results alongwith time settlement curves and load
settlement curve in both natural and log graph, variation of
Modulus of subgrade reaction with size, shape and depth of
foundation.
c) If piling is envisaged, the following shall be indicated with
comprehensive supporting calculations:
i) Type of pile and reasons for recommending the same
duly considering the soil characteristics.
ii) Suitable founding strata for the pile.
iii) Estimated length of pile for 500 KN (400 mm dia), 750
KN (450 mm dia), 1000 KN (500 mm dia) and 4500
KN (1070 mm dia) capacities. End bearing and
frictional resistance shall be indicated separately.
iv) Magnitude of negative skin friction, if any, to be
considered in pile design.
2.5.4 Additional Recommendations
a) Coefficient of permeability of various sub soil and rock strata based on
in-situ permeability tests.
b) Cone resistance, frictional resistance, total resistance, relation between
cone resistance and Standard Penetration Test N Value, and settlement
analysis for different sizes of foundation as specified based on static
cone penetration test.
c) Electrical resistivity of sub-soil based electrical resistivity tests
including electrode spacing vs cumulative resistivity curve.
d) Suitability of the soil for construction of roads and pavements, their
stable slopes for shallow and deep excavations, active and passive
earth pressures at rest and modulus of elasticity as a function of depth
for the design of underground structures.
e) Suitability of locally available soils at site for filling and back filling
purposes.
f) If expansive soil is met with, recommendation on removal or
retainment of the same under the foundation etc. shall be given. In the
latter case, detailed specifications of any special treatment required
including specifications for materials to be used, construction method,
equipments to be deployed, etc. shall be furnished.
g) Protective measures based on chemical nature of soil and ground water
with due regard to potential deleterious effects on concrete, steel and
other building materials, etc. Remedial measures for sulphate attack
and acidity shall be dealt in detail. Susceptibility of soil to termite
action and remedial measures for the same.
h) Susceptibility of sub soil strata to liquifaction in the event of
earthquake. If so, recommendation for remedial measures.
i ) Any other information of special significance like dewatering schemes,
etc. which may have a bearing on the design and construction ,
j) Recommendations for additional soil investigation beyond the scope of
the present work if the Contractor considers such investigation is
necessary.
2.6 Rates and Measurements
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The clauses below shall apply for item rate contracts only. They shall not be
applicable to turn key and lumpsum contracts, except for work beyond the
scope of such contracts.
2.6.1 Rates
a) The item of work in the Schedule of Quantities describes the work very
briefly. The various items of the Schedule of Quantities shall be read in
conjunction with the corresponding sections in the technical
specifications including amendments and additions, if any. For each
item in the Schedule of Quantities, the bidder's rates shall include for
the activities covered in the description of the item as well as for all
necessary operations in details described in this technical specification.
b) The unit rates quoted shall include minor details which are obviously
and fairly intended, and which may not have been included in these
documents but are essential for the satisfactory completion of the work.
c) The bidders quoted rates shall be inclusive of providing all plant
equipments, men, materials, skilled and unskilled labour; making
observations establishing the ground level and coordinates at location
of each borehole, test pit, etc. by carrying levels from one established
bench mark and distances from one set of grid lines furnished by the
Owner. Also, no extra payments shall be made for conducting the
Standard Penetration Test; collecting, packing, transporting of all
samples and cores; recording of all results and submitting them in
approved formats.
d) No claims shall be entertained if the details are shown on the released
for construction drawings differ in any way (e.g .location and depth for
tests, number of tests, etc.) from those shown on the tender drawings.
2.6.2 Measurements
a) All measurements shall be in SI Units.
b) Lengths shall be measured in meters (m) correct to two places of
decimals. Areas shall be worked out in square meters (m2) and volume
in cubic meters and which may not have been included in these
documents but are essential for the satisfactory completion of the work.
c) The bidders quoted rates shall be inclusive of providing all plant
equipments, men, materials, skilled and unskilled labour; making
observations establishing the ground level and coordinates at location
of each borehole, test pit, etc. by carrying levels from one established
bench mark and distances from one set of grid lines furnished by the
Owner. Also, no extra payments shall be made for conducting the
Standard Penetration Test; collecting, packing, transporting of all
samples and cores; recording of all results and submitting them in
approved formats.
d) No claims shall be entertained if the details are shown on the released
for construction drawings differ in any way (e.g. location and depth for
tests, number of tests, etc.) from those shown on the tender drawings.
2.6.2 Measurements
a ) All measurements shall be in SI Units
b) Lengths shall be measured in meters (m) correct to two places of
decimals. Areas shall be worked out in square meters (m2) and volume
in cubic meters (m3), rounded off to two decimals.
c) Certain tests have to be conducted in bore holes, trial pits, etc. Such
boreholes, trial pits, etc., shall be measured only once and not again
just because of a tests are conducted therein.
2.7 Specific Requirements for Geotechnica1 investigation at River Crossings
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The entire soil investigation work shall be carried ~ out in accordance with the
relevant parts of the specification for geotechnical investigation. Standard
Penetration test at River Crossings and special locations shall be carried out at
the interval of 2.0, 3.0, 5.0, 7.0, 10.0 and thereafter at the rate of 3m intervals
to 40m. However in each bore holes undisturbed samples shall be collected at
every change of strata and at depths as follows: 1.0m, 4.0m, 7.0m, 11.0m and
thereafter at the rate of 3m intervals up to 38m. The spacing between the top
levels of undisturbed sampling and standard, penetration testing shall not be
less than 1.0m. The boreholes shall generally be executed to, specified depth
as per specifications or as shown in the drawing. If refusal strata is reached
(i.e. SPT-N Value is greater than 100 continuously for 5m depth) the borehole
may be terminated at shallower depth i.e. at 5m in refusal strata.
2.8 Summary of Results of Laboratory Tests on Soil and Water Samples
B
O
R
E
H
O
L
E/
T
RI
A
L
PI
T
N
O.
D
E
P
T
H
(
m
)
T
Y
P
E
O
F
S
A
M
P
L
E
DENSITY
(KN/Cu.m.)
Bulk Dry
W
A
T
E
R
C
O
N
T
E
N
T
(
%
)
PARTICLE SIZE (%) CONSISTANCY
PROPERTIES
SOIL
GRAVEL SAND SILT CLAY L.L. P.L. P.I. CLA
SSIF
ICA
TIO
N –
IS
D
E
S
C
R
I
P
T
I
O
N
S
P
E
C
I
F
I
C
G
R
A
V
I
T
Y
Notations :
I. For type of sample II. For Strength TestDB Disturbed Bulk Soil sample PMT Pressuremeter TestDP Disturbed SPT soil sample SCPT Static Cone Penetration TestDS Disturbed Samples from cutting edge UCC Unconfined Compression Test
Of Undisturbed soil sample VST Vane Shear TestRM Remoulded soil sample Tuu Unconsolidated Undrained Triaxial TestUB Undisturbed soil sample Tcu Consolidated UndrainedUS Undisturbed Soil Sample by Sampler Triaxial Test with Pore PressureW Water Sample Ted Consolidated Drained Triaxial Test
(Note : 1. Replace T by D for Direct Shear Test)
STRENGTH TEST CONSOLIDATION TEST
TYPE C ec pc Cc P mv Cv
SHRINKAGELIMIT(
%)
SWELL TEST COMPACTION TEST
S. Pr F S M.D.D. O.M.C. C.B.R.
RELATIVEDENSITY(%)
PERMEABILITY (m/hour)
REMARKS
III. For Others Cv Coefficient of consolidation (sq.m./hr)LL Liquid Limit (%) MDD Maximum Dry Density (KN/Cu.m.)PL Plastic Limit (%) OMC Optimum Moisture Content (%)PI Plasticity Index (%) CBR California Bearing Ratio (%)C Cohesion (KN/Sq.m.) IV. For Chemical Test Angle of Internal friction (degrees)S. Pr. Swelling Pressure (KN/Sq.m.) pH pH valueFSI Free Swell Index (%) Cl Chlorine Contentec Initial Void Ratio SO3 Sulphate ContentPf Preconsolidation Pressure (KN/Sq.m.) NO4 Nitrate ContentCc Compression Index CO3 Carbonate ContentP Pressure range (KN/Sq.m.)Mv Coefficient of volume compressibility (Sq.m./KN)
2.9 Tools and Plants for Soil Investigations.
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A. Sampling, S.P.T.
i) Tripod
ii) Shell and Augar
iii) Augar and wash boring
iv) Pump
v) Casing
vi) Chaintong
vii) Drill rod
viii) Pipes
ix) Monkey weight (For S.P.T.)
x) Winch (Man/Mechanically operated)
xi) Cathead
xii) Sockets
xiii) Samples
a) Open drive thin wall sampler
b) Tube Sampler
c) Split Spoon Sampler
d) Piston sampler (Bishop Sampler)
xiv) Polythin Packet
B. Other Test Apparatus
i) Vane Shear (4 blade vane)
ii) Dynamic cone (50mm and 65 mm diameter with apex angle 60 Deg.)
The following laboratory tests are usually conducted from the soil samples
collected:
i) Visual examination and other identification tests.
ii) Determination of in-situ density (r).
iii) Determination of strength parameters, namely, cohesion C and angle of
internal friction 0, settlement characteristic such as rate of settlement
(D/t), compression index Cc etc. and
iv) Determination of; elastic properties-Modulus of compressibility (k),
coefficient of lateral subgrade reaction (C), etc.
Among the field tests, the Standard Penetration Test (SPT) is extensively
adopted. In the Standard Penetration Test (SPT), a 64 Kg weight is dropped
76 cm to drive a sampling spoon into the ground. The no. of blows required to
push the spoon to a given depth is corelated with a no. of soil properties. The
advantage of SPT is that it is relatively quick, simple and inexpensive; but it is
also subjected to many kind of errors. Also, correlations of SPT measurements
with those of soil stress and other parameters are not particularly reliable.
In the Standard Core Penetration test, a shaft with a conical tip is slowly
pushed into the ground while electrical transducers measure both tip pressure
and side friction. The SCPT generally gives more accurate measurement than
the SPT. It is also a faster method to identify problem soils.
The SPT value N obtained from the field, is corrected for overburden pressure
in accordance with the chart shown in Fig. 2. The SCPT gives the point
resistance qc and side friction fc.
The SPT value N and the SCPT value qc are related as shown in table (1)
below. Table (1) - Correlation between SPT value N and SCPT value qc
Soil Type q/n
Clays 2.0
Silt, sandy silt and slightly cohesive silt and mixture 2.0
Clean fine to medium sands and slightly silty sands
Coarse
3-4
Sands and sands with little gravel 3-6
Sandy gravels and gravel 8-10
1.3 Properties of Soil
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The following soil properties are used in the design of different type of
foundations:
1. Density
2. Relative density Dr
3. Angle of internal friction for sandy soil
4. Unconfined compressive strength Cu and cohesion C for clayey soil.
5. Modules of compressibility Es
6. Coefficient of lateral subgrade modules (C for sand and k for clay)
7. Poisson's Ratio n
8. Compressive strength of rocks s
9. Ultimate bond strength of rock-anchor interface.
Table below gives the above properties and classify the soils and rocks.
1.4 Data For Foundation Design
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The following data are usually required for a proper selection of type of
foundation, its design and construction:
1. Route map showing proposed layout of tower and topography.
2. Selection of soil pits for soil data.
3. Selection of sites for SPT.
4. General layout of the tower and the loads at the foundation level.
5. Meteorological data " wind, earthquake and frost penetration
particulars.
6. Max. allowable settlement at the base of the tower considering the
permissible deflection at the top as H/140.
7. In the case of river crossings:
a. A site plan with details of crossing of at least 90m upstream and
downstream from the central line of the crossing.
b. Outline of banks.
c. Direction of flow of water.
d. Alignment of crossing and location of towers.
e. A cross section of the river at the proposed site of crossing, showing
bed-line, banks, ordinary flood level, low water level, the highest
flood, estimated depth of scour etc.
f. The maximum and mean velocity of water current.
Notes:
1. For non-cohesive soils the value of safe bearing capacity are to be
reduced by 50 percent if the water table is above or near the base of
footing.
2. The values of safe bearing capacities do not take into effect the shape
and size of footing, cohesion C, angle of internal friction 0, effect of
eccentricity, the SPT value N, etc. Hence, the values are to be
considered as average and approximate.
3. For other types of soil such as black cotton and peat, soil investigations
have to be necessarily carried out for determining the safe bearing
capacity.
Table (2) Relation between N, c, Dr, for sandy soil
Description SPT value (N) Density ()gm/cc
Relativedensity Dr
Angle ofinternal friction
Very loose 0-4 1.1 to 1.6 0-15 <28
Loose 4-10 1.45 to 1.85 15-35 28-30Medium 10-30 1.75 to 2.1 35-65 30-36Dense 30-50 1.75 to 2.25 65-85 36-41
Very Dense >50 2.1 to 2.4 85-100 >41
Table (3) Relation between N value, and unconfined compressive
strength Cu and cohesion C for clays
Consistency SPT Value N Unconfinedcompressivestrength C
kg/cm2
Cohesion Ckg/cm2
Reductionfactor for sidefriction a of
bore pileSoft 0-4 0-0.5 0-0.25 0.7
Medium 4-8 0.5-1.0 0.25-0.5 0.5Stiff 8-15 1.0-2.0 0.5-1.0 0.4
Very stiff 15-30 2.0-4.0 1.0-2.0 0.3Hard >30 >4.0 >2 0.3
Table (4) Safe bearing capacity
Type of rocks/soils Safe bearingcapacity Kg/cm2
RocksRocks hard without lamination such as granite 33Laminated rocks such as sand stone 16.5Rock desposits such as shale 9.0Soft rock 4.5Non-cohesive soils
Gravel, sand and gravel, compact and offering high resistance topenetration when excavated by tools
4.5
Coarse sand, compact and dry 4.5Medium sand, compact and dry 2.5Fine sand, silt (dry lumps easily pulverized by the fingers) 1.5Loose gravel or sand gravel mixture loose coarse to medium sand, dry 2.5Fine sand, loose and dry 1.0Cohesive soilsSoft shale, hard or stiff clay in deep bed dry 4.5Medium clay, readily indented with a thumb nail 2.5Moist clay and sand clay mixture which can be indented with strongthumb pressure
1.5
Soft clay indented with moderate thumb pressure 1.0Very soft clay which can be penetrated several inches with the thumb 0.5Black cotton soil or other shrinkable or expansive clay in dry condition(50 percent saturation)
1.5
Table (5) Modulus of compressibility E, and Poisson’s ratio for soils
Soil type Modulus of compressibilityE. kg/cm2
Ratio
ClayVery soft 3-30 0.1- 0.5Soft 20-40Medium 45-90Hard 70-200Silt 20-200 0.3-0.35SandSilty 50-200Loose 100-250 0.2-0.4Dense 500-1,000GravelLoose 500-1400 Reliable dataDense 800-2000 Not available
One sample per lotof 200 cubic meteror part thereof fromeach source foreach size
IS : 383, IS : 2386and POWERGRIDspecification
POWERGRIDapproved lab
Each source tobe approved byPOWERGRID.Review andacceptance oftest result byPOWERGRID.
B
* Applicable to design mix concretes only. ** Applicable to concrete work subject to frost action.
STANDARD FIELD QUALITY PLANFOR TRANSMISSION LINE PACKAGES
Section : FOUNDATION MATERIALS
Sl. No. Component/Operation & Description of
Test
Sampling Planwith basis
Ref. Document &acceptance norm
TestingAgency
Remarks Check
C) FINE AGGREGATE
i)
ii)
iii)
iv)
v)
vi)
vi)
Gradation/Determination of Particle size(Sieve Analysis)
Specific Gravity anddensity*
Moisture Content*
Absorption Value*
Builking*
Silt Content Test
Presence ofdeleterious materials
One sample perlot of 200 cubicmeter or partthereof fromeach source
IS : 383, IS : 2386, IS :4031, IS : 236, IS : 456and POWERGRIDSpecification
POWERGRID approvedlab
Each source tobe approved byPOWERGRID.Review andacceptance oftest result byPOWERGRID
B
D) WATER
i) Cleanliness (VisualCheck)
100% IS : 456, IS : 3205 andPOWERGRIDspecification. The waterused for mixing concreteshall be fresh, clean andfree from oil, acids andalkalies, organicmaterials, or otherdeleterious materials
Contractor Each source tobe approved byPOWERGRID
C
ii) Suitability of water forRCC work
One sample persource
POWERGRIDspecification. Potablewater is generallysuitable for concreting.
One sample per lot of 40 MTor part thereof for each sizeof steel conforming to IS :1139 and 5 MT or partthereof for HDS wire foreach size of steel as per IS :432. For steel as per IS :1786 under 10 mm 1sample for each 25 MT orpart thereof. 10 mm – 16mm 1 sample for each 35MT or part thereof. Over 16mm 1 sample for each 45MT or part thereof.
IS : 432, IS :1139, IS : 1786 &POWERGRIDspecification
Manufacturers/POWERGRIDapproved lab
Review ofmanufacturerstest certificatesas well as labtest result byPOWERGRID
B
vii) Reverse Bend Testfor HDS wire
One sample per lot of 5 MTor part thereof for each size
IS : 432POWERGRIDspecification
Manufactu-rer/POWER-GRID appro-vedlab
Review ofmanufactu-rerstest certificatesas well as labtest result byPOWERGRID
Records to bekept duly signedby POWERGRIDand contractor
A
Section : GENERAL GUIDELINES FOR IMPLEMENTATION
1. Details of categories of check codes A, B & C including accepting anddeviation dispositioning authorities are indicated at Annexure-I.
2. POWERGRID specification shall mean POWERGRID technicalspecification, approved drawings/data sheets and LOA provisionsapplicable for the specific contract.
3. Acceptance criteria and permissible limits for certain tests areindicated at Annexure-II. For balance tests, site to verify the samewith respect to POWERGRID specification, relevant Indian Standardsand/or prevalent code of practice.
4. It is clarified that the tests indicated at column 2 of this FQP i.e.against column "Component operation & Description of Test," areonly generally required to be conducted. However, POWERGRIDreserves the right to carry-out any additional tests at any stage if thesituation so warrants.
5. POWERGRID site representative shall witness all the tests conductedby the contractor as mentioned in this FQP. However, in case oftests conducted in the POWERGRID approved lab, it is preferred towitness the tests in the lab itself, if possible.
6. Head of GHQ shall approve testing laboratory before accepting thetest results from the lab.
7. Head of GHQ shall approve the sources for cement, coarseaggregate, fine aggregate & water before actual utilisation.
8. All the testing & measuring equipments used by the contractor fortesting are required to be calibrated. A copy of valid calibration reportshall be retained by POWERGRID as records.
9. Classification of foundations shall be approved by POWERGRIDbased on the Joint Inspection Report & soil investigation reports.
10. Curing of concrete work should be continued for a minimum period of10 days.
11. Zone-IV fine aggregate shall not be used for concreting work.
Section : GENERAL GUIDELINES FOR IMPLEMENTATION
12. Identification and traceability records in the standard formats forvarious materials in line with QA&I circular dated 7-5-96 shall bemaintained and retained in POWERGRID.
13. CEMENT
13.1 In case supply of cement is in the scope of the contractor, the sameshall be procured from sources approved by POWERGRID site andgot tested at site on sample basis for specified acceptance tests asspecified in this FQP at a reputed Third Party Lab approved byPOWERGRID site.
13.2 The samples of cement for site testing shall be taken within threeweeks of the delivery and all the tests shall be commenced within oneweek of sampling.
14. REINFORCEMENT STEEL
14.1 In case supply of reinforcement steel is in the scope of the contractor,the same shall be procured from the main producers i.e. SAIL,TISCO, IISCO or Rashtriya Ispat Nigam or the rerollers approved bymain producers. The reinforcement steel shall be got tested at siteon sample basis for specified acceptance tests as specified in thisFQP at a reputed Third Party Lab approved by POWERGRID site.
14.2 The results of the testing of cement and reinforcement steel referred to in13.1 and 14.1 above shall be got approved from POWERGRID site beforecement and reinforcement steel are put to use. However, in exceptionalcases due to exigencies of work., POWERGRID site may authorise thecontractor to use Cement and Reinforcement Steel even before the testresults are received. However, in all such cases, if the test resultssubsequently received are found to be not complying with the specifiedacceptance criteria, the contractor shall have to dismantle and recast all suchfoundations cast with such non-conforming materials at his own cost.Confirmation to this effect shall be obtained from the contractor by the Projectauthorities beforehand in all such cases.
ANNEXURE-IPAGE 1 OF 1
ACCEPTING AND DEVIATION DISPOSITIONING AUTHORITIES FORDIFFERENT CATEGORIES
OF CHECKS AS ENVISAGED IN FIELD QUALITY PLAN
CATEGORY TYPE OFCHECK
100% CHECKING/WITNESSING BY
COUNTERCHECK/SURVEILLANCE
CHECK BY
ACCEPTINGAUTHORITY, IF TEST
RESULTS ARE WITHINPERMISSIBLE LIMITS
DEVIATIONDISPOSITIONING
AUTHORITY
A CRITICAL EXECUTING DEPTT.PLUS FQA
REPRESENTATIVEGHQ
FQA REPRESENTATIVEAND RHQ/DHQ
REPRESENTATIVE
HEAD OF DHQ HEAD OF RHQ INCONSULTATION
WITH CQA, IFREQUIRED
B MAJOR EXECUTING DEPTT. DHQ REPRESENTATIVE HEAD OF GHQ HEAD OF DHQC MINOR CONTRACTORS
REPRESENTATIVEEXECUTING DEPTT. MINIMUM E4 LEVEL
EXCUTIVE OF SUB-STATION/TL
HEAD OF GHQ
ANNEXURE-IIPAGE 1 OF 3
ACCEPTANCE CRITERIA AND PERMISSIBLE LIMITS FOR FOUNDATION MATERIALS & CONCRETE
(iv) Deleterious Materials : Total deleterious material shall not be more than 5% byweight.
(D) REINFORCEMENT STEEL : As per relevant IndianStandards.
ANNEXURE-IIPAGE 3 OF 3
(E) CONCRETE CUBE TEST
For nominal (volumetric) concrete mixes, compressive strength for 1:1½:3 (cement :sand : Coarse aggregate) concrete shall be 265 kg/cm2 for 28 days and for 1:2:4nominal mix, it shall be 210kg/cm2.
(F) ACCEPTANCE CRITERIA BASED ON 28 DAYS COMPRESSIVE STRENGTH FORNOMINAL MIX CONCRETE
a) The average of the strength of three specimen be accepted as thecompressive strength of the concrete, provided the strength of any individualcube shall neither be less than 70% nor higher than 130% of the specifiedstrength.
b) If the actual average strength of accepted sample exceeds specified strengthby more than 30%, the Engineer-in-charge, if he so desires, may furtherinvestigate the matter. However, if the strength of any individual cubeexceeds more than 30% of specified strength, it will be restricted to 30% onlyfor computation of strength.
c) If the actual average strength of accepted sample is equal to or higher thanspecified strength upto 30%, then strength of the concrete shall beconsidered in order and the concrete shall be accepted at full rates.
d) If the actual average strength of accepted sample is less than specifiedstrength but not less than 70% of the specified strength, the concrete may beaccepted at reduced rate at the discretion of Engineer-in-Charge.
e) If the actual average strength of accepted sample is less than 70% ofspecified strength, the Engineer-in-Charge shall reject the defective portionof work represented by sample and nothing shall be paid for the rejectedwork. Remedial measures necessary to retain the structure shall be taken atthe risk and cost of contractor. If, however, the Engineer-in-Charge sodesires, he may order additional tests to be carried out to ascertain if thestructure can be retained. All the charges in connection with these additionaltests shall be borne by the Contractor.
(G) ACCEPTANCE CRITERIA FOR DESIGN MIX CONCRETE SHALL BE ASPER IS:456