Soil Stabilization - HBTU KANPUR

Use of Locally Available Materials

and Soil Stabilisation Technique

Dr. Deepesh Singh

Assistant Professor Dept. of Civil Engineering

H.B. Technological Institute, Kanpur

A Lecture

on

Soil Stabilization

The soil stabilization means the improvement of

stability or bearing power of the soil by the use of

controlled compaction, proportioning and/or the

addition of suitable admixture or stabilizers.

Basic Principles of Soil Stabilization….

• Evaluating the properties of given soil

• Deciding the lacking property of soil and choose

effective and economical method of soil stabilization

• Designing the Stabilized soil mix for intended stability

and durability values

• Web resource provided by Dr. M.S. AMARNATH, Bangalore University, Bangalore and IRC : SP-26

Need for Soil Stabilization

Limited Financial Resources to Provide a complete network Road System to build in conventional method

To improve certain undesirable properties of soils e.g. excessive swelling and shrinkage, high plasticity, difficulty in compaction etc.

Effective utilization of locally available soils and other suitable stabilizing agents.

Encouraging the use of Industrial Wastages in building low cost construction of roads.


Methods of Soil Stabilization

•Mechanical Stabilization

•Soil Cement Stabilization

•Soil Lime Stabilization

•Soil Bitumen Stabilization

• Lime Fly ash Stabilization

• Lime Fly ash Bound Macadam.


Mechanical Stabilization

• This method is suitable for low volume roads

i.e. Village roads in low rainfall areas.

• This method involves the correctly

proportioning of aggregates and soil,

adequately compacted to get mechanically

stable layer

• The Basic Principles of Mechanical Stabilization

are Correct Proportioning and Effective

Compaction


Desirable Properties of Soil-Aggregate Mix

• Adequate Strength

• Incompressibility

• Less Changes in Volume

• Stability with Variation in water content

• Good drainage, less frost Susceptibility

• Ease of Compaction.


Factors Affecting Mechanical

Stabilization

Mechanical Strength of aggregates

Gradation

Properties of the Soil

Presence of Salts

Compaction


Mechanical Strength

• When the soil is used in small proportion to fill

up the voids the crushing strength of aggregates

is important

Gradation

• A well graded aggregate soil mix results in a mix

with high dry density and stability values

Properties of soil

• A mix with Plasticity Index, results poor stability

under soaking conditions. Hence it is desirable to

limit the plasticity index of the soil


Presence of Chemicals

• Presence of Salts like Sulphates and mica

are undesirable

• Presence of Calcium Chloride is Beneficial

Compaction

• Effective Compaction is desirable to

produce high density and stability mix


Soil Cement Stabilization

• Soil Cement is an intimate mix of soil,

cement and water, compacted to form a

strong base course

• Cement treated or cement modified soil

refers to the compacted mix when cement is

used in small proportions to impart some

strength

• Soil Cement can be used as a sub-base or

base course for all types of Pavements


Factors affecting soil cement stabilization

• Soil

• Cement

• Pulverisation and Mixing

• Compaction

• Curing

• Additives


Soil

THE PHYSICAL PROPERTIES

• Particle Size Distribution

• Clay content

• Specific Surface

• Liquid limit and Plasticity Index

Cement

A increase in cement content generally

causes increase in strength and durability


Pulverisation and Mixing

• Better the Pulverisation and degree of mixing,

higher is the strength

• Presence of un pulverised dry lumps reduces

the strength

Compaction

• By increasing the amount of compaction dry

density of the mix, strength and durability also

increases


Curing

Adequate Moisture content is to be retained in

order to accelerate the strength

Additives

There are some additives to improve properties

• Lime

• Sodium hydroxide

• Sodium Carbonate

• Calcium Chloride


Design of Soil –Cement Mix

• Soil – Cement specimens are prepared with

various cement contents in constant volumes

moulds

• The compressive strength of these specimens

tested after 7 days of curing

• A graph is plotted Cement content Vs

compressive strength

• The Cement Content Corresponding to a

strength of 17.5 kg/cm2 is taken as design

cement content


Soil Lime Stabilization

• Soil- Lime has been widely used as a

modifier or a binder

• Soil-Lime is used as modifier in high plasticity

soils

• Soil Lime also imparts some binding action

even in granular soils


Soil-Lime is effectively used in Expansive

soils with high plasticity index.


Factors affecting Properties of Soil-Lime

Lime Content

• Generally increase in lime content causes

slight change in liquid limit and considerable

increase in Plasticity index

• The rate of increase is first rapid and then

decreases beyond a certain limit

• The point is often termed as lime fixation

point

This is considered as design lime content


Type of Lime

After long curing periods all types of limes

produce same effects. However quick lime has been found more effective than hydrated lime

Calcium Carbonate must be heated at higher temperature to form Quick lime calcium oxide( CaO)

Calcium oxide must be slaked ( by the addition of water) to form Hydrated lime

Compaction Compaction is done at OMC and maximum

dry density. • Web resource provided by Dr. M.S. AMARNATH, Bangalore University, Bangalore and IRC : SP-26

Curing

• The strength of soil-lime increases with curing

period upto several years. The rate of

increase is rapid during initial period

• The humidity of the surroundings also affects

the strength

Additives

• Sodium metasilicate, Sodium hydroxide and

Sodium Sulphate are also found useful

additives


Soil- Bituminous Stabilization

• The Basic Principles of this stabilization are

Water Proofing and Binding

• By Water Proofing inherent strength and

other properties could be retained

• Most Commonly used materials are Cutback

and Emulsion

• Bitumen Stabilized layer may be used as

Sub-base or base course for all the roads


Factors affecting properties of soil-bitumen

Soil

• The particle size, shape and gradation of the

soil influence the properties of the soil-bitumen

mix.

Types of Bitumen

• Cutbacks of higher grade should be preferred

• Emulsions generally gives slightly inferior

results than Cutback.


Amount of Mixing

• Increasing proportion of bitumen causes a

decrease in dry density but increases the

stability after a certain bitumen content

• The optimum bitumen content for maximum

stability generally ranges from 4 to 6%

Mixing

• Improved type of mixing with low mixing period

may be preferred


Compaction

• Effective Compaction results higher

stability and resistance to absorb water

Additives

• Anti stripping and reactive chemical

additives have been tried to improve the

properties of the mixes

• Portland cement can also be used along with

the soil bitumen


Use of Locally Available Materials in Road Construction

Necessity Scarcity of good quality

aggregates / soil for road construction

Production and accumulation of different waste materials

Disposal and environmental problem

Economical and gainful utilisation


Limitations of Using Waste Materials

Quality of waste is not controlled by their manufacturers

Characteristics of by-products vary in a wide range

Road construction practice is accustomed to traditional materials of steady quality

Specifications of layers compaction of traditional materials are not suitable for waste materials


General Criteria for Use of Waste Materials

Amount of yearly produced waste material should reach a certain lower limit

The hauling distance should be acceptable

The material should not have a poissonous effect

The material should be insoluble in water

The utilisation should not have a pollutional effect to the environment


Special Requirement for Using Waste Materials

Free from organic matter

Should not swell or decay as influenced by water

Should not be soluble in water

Particles should be moderately porous


Industrial wastes

Thermal Power Stations

* Fly ash

* Bottom ash

* Pond ash

Steel Plants

* Blast furnace slag

* Granulated blast furnace slag

* Steel slag


Utilisation of fly ash

Thermal power - Major role in power generation

Indian scenario - Use of coal with high ash content

- Negligible utilisation of ash produced

Bulk utilisation - Civil engineering applications like construction of roads & embankments


Can be used for construction of Embankments and backfills Stabilisation of subgrade and sub-base Rigid and semi-rigid pavements

Fly ash properties vary widely, to be characterised before use

Major constituents - oxides of silica, aluminum, iron, calcium & magnesium

Environmentally safe material for road construction

Possesses many favourable properties for embankment & road construction

Utilisation of fly ash


Favourable properties of fly ash Light weight, lesser pressure on sub-soil

High shear strength

Coarser ashes have high CBR value

Pozzolanic nature, additional strength due to self-hardening

Amenable to stabilisation

Ease of compaction

High permeability

Non plastic

Faster rate of consolidation and low compressibility

Can be compacted using vibratory or static roller


Engineering properties of fly ash Parameter Range

Specific Gravity 1.90 – 2.55

Plasticity Non plastic

Maximum dry density (gm/cc) 0.9 – 1.6

Optimum moisture content (%) 38.0 – 18.0

Cohesion (kN/m2) Negligible

Angle of internal friction (j) 300 – 400

Coefficient of consolidation Cv (cm2/sec) 1.75 x 10-5 – 2.01 x 10-3

Compression index Cc 0.05 – 0.4

Permeability (cm/sec) 8 x 10-6 – 7 x 10-4

Particle size distribution (% of materials)

Clay size fraction

Silt size fraction

Sand size fraction

Gravel size fraction

1 – 10

8 – 85

7 – 90

0 – 10

Coefficient of uniformity 3.1 – 10.7

Differences between Indian & US fly ashes

Property compared Indian fly ash US fly ash

Loss on ignition (Unburnt carbon)

Less than 2 per cent

5 to 8 per cent

SO3 content 0.1 to 0.2 per cent

3 to 4 per cent

CaO content 1 to 3 per cent 5 to 8 per cent

Increase in concentration of heavy metals

3 to 4 times in comparison to source coal

10 times or more in comparison to source coal

Rate of leaching Lower Higher

Fly ash for road embankment

Ideally suited as backfill material for urban/ industrial areas and areas with weak sub soils

Higher shear strength leads to greater stability

Design is similar to earth embankments

Intermediate soil layers for ease of construction and to provide confinement

Side slope erosion needs to be controlled by providing soil cover

Can be compacted under inclement weather conditions

15 to 20 per cent savings in construction cost depending on lead distance


Fly ash for road embankment

Earth Cover

Earth Cover

Bottom ash or Pond ash

Typical cross section of fly ash road embankment


Approach embankment for second Nizamuddin bridge at Delhi

– Length of embankment - 1.8 km

– Height varies from 6 to 9 m

– Ash utilised - 1,50,000 cubic metre

– Embankment opened to traffic in 1998

– Instrumentation installed in the embankment showed very good performance

– Approximate savings due to usage of fly ash is about Rs.1.00 Crore


Approach embankment for second Nizamuddin bridge at Delhi


Spreading of pond ash

Compaction of pond ash

Second Nizamuddin bridge approach embankment


Stone pitching for slope protection

Traffic plying on the embankment

Second Nizamuddin bridge approach embankment


Utilisation of fly ash Four laning work on NH-6 (Dankuni to Kolaghat)

Water logged area

(soft ground conditions)

Compaction of fly ash over layer of geotextile

Length of stretch – 54 km

Height of embankment – 3 to

4 m

Fly ash utilisation – 2 Million

cubic metres


Reinforced fly ash embankment

Fly ash - better backfill material for reinforced embankments

Polymeric reinforcing materials – Geogrids, friction ties, geotextiles

Construction sequence – similar to reinforced earth structures


Okhla flyover approach embankment

– First geogrid reinforced fly ash approach embankment constructed in the country

– Length of embankment – 59 m

– Height varied from 5.9 to 7.8 m

– Ash utilised – 2,700 cubic metre

– Opened to traffic in 1996

– Performance has been very good


Pond Ash Fill

7.8 to 5.9 m

Facing panels

Filter medium Geogrids

Reinforced foundation mattress of bottom ash




Erection of facing panels

Rolling of pond ash


Support provided to facing panels during construction

Laying of geogrids



Hanuman Setu flyover approach embankment

– Geogrid reinforced fly ash approach embankment

– Length of embankment – 138.4 m

– Height varied from 3.42 m to 1.0 m

– Opened to traffic in 1997


Sarita Vihar flyover approach embankment

– Length of embankment – 90 m

– Maximum height – 5.25 m

– Embankment opened to traffic in Feb 2001

– Polymeric friction ties used for reinforcement


Sarita Vihar flyover reinforced approach embankment

Arrangement of friction ties before

laying pond ash

Laying of friction ties


Compaction using plate vibrator near

the facing panels

Compaction of pond ash using static and vibratory rollers

Sarita Vihar flyover reinforced approach embankment


Fly ash for road construction Stabilised soil subgrade & sub-

base/base courses – Mixing with soil reduces plasticity

characteristics of subgrade

– Addition of small percentage of lime or cement greatly improves strength

– Leaching of lime is inhibited and durability improves due to addition of fly ash

– Pond ash & bottom ash can also be stabilised

– Lime-fly ash mixture is better alternative to moorum for construction of WBM / WMM


Construction of semi-rigid/ rigid pavements

– Lime-fly ash concrete

– Dry lean cement fly ash concrete

– Roller compacted concrete

– Fly ash admixed concrete pavements

– Lime-fly ash bound macadam

– Precast block paving

– High performance concrete

Fly ash for road construction


WBM Gr II/WMM 150 mm

WBM Gr III/WMM 75 mm

GSB 350 mm

BM 75 mm

DBM 100 mm

Bituminous concrete 40 mm

Typical cross section of flexible pavement – conventional section


Fly ash + 6% cement stabilised layer 150 mm

Typical cross section of flexible pavement – using fly ash

WBM Gr III/WMM 75 mm

Pond ash 350 mm

BM 75 mm

DBM 100 mm

Bituminous concrete 40 mm


Pond ash 300 mm

DLFC 100 mm

Fly ash admixed PQC 300 mm

Typical cross section of rigid pavement – using fly ash


Demonstration road project at Raichur

Total length of the road – 1 km

Five sections of 200 m each with different

pavement sections

Pond ash has been used for replacing moorum

in sub-base course

Stabilised pond ash used for replacing part of

WBM layer

One rigid pavement section using DLFC and

RCCP technology was laid

Performance of all the specifications is good • Web resource provided by Dr. M.S. AMARNATH, Bangalore University, Bangalore and IRC : SP-26

Mixing of lime stabilised pond ash

Compaction of stabilised pond ash

using road roller

Demonstration road project using fly ash at Raichur


Construction of roller compacted concrete pavement

View of the demonstration road

stretch after three years

Demonstration road project using fly ash at Raichur


A rural road near Dadri in District Gautam Budh Nagar, Uttar Pradesh was selected

Total length of road – 1.4 km

Bottom ash used as embankment fill

Base course constructed using fly ash stabilised with 8% cement

RCCP Wearing course – 10 cm thickness

RCCP Mix proportion – 1:2:4

30 per cent of cement and 20 per cent of sand replaced with fly ash in RCCP

Shoulders – 8% cement stabilised fly ash

Demonstration road project using fly ash near Dadri (U.P)


Bottom ash

RCCP wearing course - 0.1 m

Stabilised fly ash

base - 0.1 m

Stabilised fly ash

Shoulder

Soil cover

Demonstration road project using fly ash near Dadri (U.P) – Typical section


Stabilised base course

Compaction of RCCP Mixing & laying of RCCP

Demonstration road project using fly ash near Dadri

(U.P)


IRC Guidelines / Specifications

Guidelines available on pavement construction

IRC 60 ‘Tentative guidelines for use of lime fly ash concrete as pavement base or sub-base’

IRC 68 ‘Tentative guidelines on cement fly ash concrete for rigid pavement construction’

IRC 74 ‘Tentative guidelines for lean cement concrete and lean cement fly ash concrete as a pavement base or sub-base’

IRC 88 ‘Recommended practice for lime fly ash stabilised soil as base or sub-base in pavement construction’


Guidelines for use of fly ash in road embankments

Published recently by Indian Roads Congress (SP- 58:2001)

Includes design aspects also

Handling and construction

– Loose layer thickness of 400 mm can be adopted if vibratory rollers are used

– Moisture content - OMC + 2 per cent

– Use of vibratory rollers advocated

– Minimum dry density to be achieved - 95 per cent of modified Proctor density

– Ash layer and side soil cover to be constructed simultaneously


Utilisation of steel slags

Total production of slag from steel industries is about 8.0 million tonnes

Types of slags

– Blast furnace slag

Granulated blast furnace slag (GBFS)

Air cooled slag

– Steel slag


Granulated blast furnace slag

Contains reactive silica

Suitable for lime / cement stabilisation

Air cooled blast furnace slag

Non – reactive

Suitable for use as coarse aggregates


CRRI work on utilisation of steel slags

Characterisation of slags produced at different steel plants

Laboratory studies on Lime-GBFS mixes

Semi-field studies on Lime-GBFS concrete

Test track studies on usage of slags in road works


Properties of air cooled slag Property Durgapur Bhilai Rourkela Delhi

Quartzite Specification requirements

Specific gravity

2.78 –

2.82

2.82 –

3.33

2.97 –

2.99 2.67 -

Water absorption (%)

1.53 –

1.72

0.58 –

1.38

0.74 –

1.29 0.48 2% Max

Los Angeles abrasion value (%)

18.80 25.00 14.28 34.00 40% Max

Impact value (%)

15.79 14.80 16.90 24.50 30% Max

Soundness value (%)

1.66 1.17 0.33 0.17 12% Max

Percentage voids

46.40 43.90 43.10 43.80 -


Steel slags

Obtained as a waste product during production of steel

Particle size varies from 80 mm to 300 microns

Compared to blast furnace slag, steel slag contains lower amount of silica, higher amounts of iron oxide and calcium oxide

Due to presence of free lime, steel slag should be weathered before using it in construction


Road projects executed under CRRI guidance using slags

Plant roads at Visakhapatnam

Test tracks in collaboration with AP PWD using slags from Visakhapatnam Steel Plant

Test tracks in collaboration with Orissa PWD using slags from Rourkella Plant

Test tracks at R&D Centre for Iron & Steel, Ranchi using Slags from Bokaro Plant


Construction of test track using slag at Orissa

Labour based techniques for construction of

stabilised layer


View of finished surface of road

constructed using slags at

Orissa

Lime stabilisation of iron slags (Orissa)


Processed municipal wastes

Processed municipal wastes utilised for construction of test track on village road near Delhi

Stabilised municipal waste used for construction of sub-base layer

Performance of stretch is good


Kimberlite tailings

Kimberlite tailings are waste produced from diamond mining

Can be used in base or sub-base course by adopting mechanical or cement stabilisation

High value of water absorption makes them unsuitable for use in bituminous pavement


Resources:

• Web resource provided by Dr. M.S. AMARNATH, Bangalore University, Bangalore.

• IRC : SP-26 : Report Containing Recommendations of IRC Regional Workshops on Rural Road Development, 1984.

THANK YOU

Soil Stabilization - HBTU KANPUR

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