Transcript Soil Stabilization

Use of Locally Available Materials
and Stabilisation Technique
Dr. M.S. AMARNATH
Bangalore University
Bangalore
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
Need for Soil Stabilization
Limited Financial Resources to Provide a
complete network Road System to build
in conventional method
 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
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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 SoilAggregate Mix
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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
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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
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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
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Sodium hydroxide
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Sodium Carbonate
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Calcium Chloride
Design of Soil –Cement Mix
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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
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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
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Compaction
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Compaction is done at OMC and maximum
dry density.
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
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Scarcity of good quality
aggregates / soil for road
construction
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Production and accumulation of
different waste materials
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Disposal and environmental
problem
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Economical and gainful
utilisation
Limitations of Using Waste Materials
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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
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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
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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
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Thermal Power Stations
* Fly ash
* Bottom ash
* Pond ash
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Steel Plants
* Blast furnace slag
* Granulated blast furnace slag
* Steel slag
Utilisation of fly ash
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Thermal power - Major role in power
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Indian scenario - Use of coal with high
generation
ash content
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Bulk utilisation -
Negligible utilisation
of ash produced
Civil engineering
applications like
construction of roads &
embankments
Utilisation of fly ash
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Can be used for construction of
 Embankments and backfills
 Stabilisation of subgrade and sub-base
 Rigid and semi-rigid pavements
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Fly ash properties vary widely, to be
characterised before use
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Major constituents - oxides of silica,
aluminum, iron, calcium & magnesium
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Environmentally safe material for road
construction
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Possesses many favourable properties for
embankment & road construction
Favourable properties of fly ash
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Light weight, lesser pressure on sub-soil
High shear strength
Coarser ashes have high CBR value
Pozzolanic nature, additional strength due to selfhardening
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
Silt
Sand
Gravel
Coefficient of uniformity
size
size
size
size
fraction
fraction
fraction
fraction
1 – 10
8 – 85
7 – 90
0 – 10
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
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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
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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
Second Nizamuddin bridge approach embankment
Compaction of pond ash
Stone pitching for slope
protection
Second Nizamuddin bridge approach embankment
Traffic plying on the
embankment
Utilisation of fly ash
Four laning work on NH-6 (Dankuni to Kolaghat)
Length of stretch – 54 km
Height of embankment – 3 to
4m
Fly ash utilisation – 2 Million
cubic metres
Water logged area
(soft ground conditions)
Compaction of fly ash over layer of geotextile
Reinforced fly ash embankment
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Fly ash - better backfill material for
reinforced embankments
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Polymeric reinforcing materials –
Geogrids, friction ties, geotextiles
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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
Okhla flyover approach embankment
Filter
medium
Facing
panels
Geogrids
Pond Ash Fill
7.8 to
5.9 m
Reinforced foundation mattress of bottom ash
Erection of facing panels
Okhla flyover approach embankment
Rolling of pond ash
Support provided to
facing panels during
construction
Okhla flyover approach embankment
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
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Length of embankment – 90 m
Maximum height – 5.25 m
Embankment opened to traffic in
Feb 2001
Polymeric friction ties used for
reinforcement
Laying of friction ties
Sarita Vihar flyover reinforced approach embankment
Arrangement of
friction ties before
laying pond ash
Compaction of pond
ash using static and
vibratory rollers
Sarita Vihar flyover reinforced approach embankment
Compaction using
plate vibrator near
the facing panels
Fly ash for road construction
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Stabilised soil subgrade & subbase/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
Fly ash for road construction
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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
Bituminous concrete 40 mm
DBM 100 mm
BM 75 mm
WBM Gr III/WMM 75 mm
WBM Gr II/WMM 150 mm
GSB 350 mm
Typical cross section of flexible
pavement – conventional section
Bituminous concrete 40 mm
DBM 100 mm
BM 75 mm
WBM Gr III/WMM 75 mm
Fly ash + 6% cement
stabilised layer 150 mm
Pond ash 350 mm
Typical cross section of flexible
pavement – using fly ash
Fly ash admixed PQC 300 mm
DLFC 100 mm
Pond ash 300 mm
Typical cross section of rigid pavement
– using fly ash
Demonstration road project
at Raichur
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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
Mixing of lime
stabilised pond ash
Demonstration road project using fly ash at Raichur
Compaction of
stabilised pond ash
using road roller
Construction of roller
compacted concrete
pavement
Demonstration road project using fly ash at Raichur
View of the
demonstration road
stretch after three years
Demonstration road project using
near Dadri (U.P)
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fly ash
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) – Typical section
RCCP wearing course - 0.1 m
Stabilised fly ash
base - 0.1 m
Stabilised fly ash
Shoulder
Soil cover
Bottom ash
Demonstration
road project using
fly ash near Dadri
(U.P)
Stabilised base course
Mixing & laying of RCCP
Compaction of RCCP
IRC Guidelines / Specifications
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Guidelines available on pavement construction
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IRC 60 ‘Tentative guidelines for use of lime fly
ash concrete as pavement base or sub-base’
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IRC 68 ‘Tentative guidelines on cement fly
ash concrete for rigid pavement construction’
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IRC 74 ‘Tentative guidelines for lean cement
concrete and lean cement fly ash concrete as
a pavement base or sub-base’
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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
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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
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– 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
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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
Specification
Quartzite requirements
Specific
gravity
2.78 –
2.82
2.82 –
3.33
2.97 –
2.99
2.67
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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
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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
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Road projects executed under CRRI
guidance using slags
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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
Lime
stabilisation
of iron slags
(Orissa)
View of finished
surface of road
constructed
using slags at
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 subbase layer
 Performance of stretch is
good
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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
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