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1. MODULE 1
Ground Improvement Techniques
(2019 scheme)
Group 1

2. Syllabus
Roll of ground improvement in foundation engineering- Classification of
ground improvement methods-different problematic soil -selection of
suitable ground improvement based on the soil condition-Emerging trends
in ground improvement-Different materials used for ground improvement
and its property Brief introduction to sustainable method of ground
improvement, Microbial methods.

3. WHAT IS GROUND IMPROVEMENT ?

4. • Ground improvement or ground modification is defined as the alteration
of site foundation soils or project earth structures to provide better
performance under design or operational loading conditions.
• Ground improvement is necessary when poor soil conditions are
encountered for the purpose at hand.
• While the poor soil conditions could readily be dealt with by excavating and
replacing the soil, or perhaps by using deep foundations, it is often more
cost effective to simply improve the soil in place through some type of
treatment.

5. NEED FOR GROUND IMPROVEMENT TECHNIQUES

6. • Reduce settlement of structures
• Improve Shear strength of Soil
• Improve Bearing Capacity of Soil
• Increase FOS against possible failure of embankment
• Reduce Shrinkage and Swelling of soils
• Increase Liquefaction Potential

7. ROLE OF GROUND IMPROVEMENT
IN FOUNDATION ENGINEERING

8. • Ground Improvement is carried out to improve the subsoil properties like
shear strength, stiffness and permeability etc. to reduce settlement of
structure foundation before the start of actual construction work.
• Where a project encounters unfavorable subsurface conditions, possible
alternative solutions are avoiding the particular site, modifying the planned
structure's design, removing and replacing unsuitable soils, or attempting
to modify the existing ground.
• Any structure constructed on the earth is supported by soil underlying it.
Foundation is an interfacing element between superstructure and the
underlying soil that transmits the loads supported by the foundation and
it's self-weight.

9. • Foundation design requires evaluation of safe bearing capacity both
immediate and long term settlement.
• The weak and compressible soils are subjected to problems related to
bearing capacity and settlement.
• Different degrees of precaution are to be taken to implement a given
design without causing any distress to adjoining structures.
• It is equally important to determine problems anticipated during
construction and work out proper construction procedure and remedial
measures in time.

10. • The construction problems may vary from site to site and many problems
are site specific.
• Expansive soils seriously affect various structures that are founded on them
due to their tendency to undergo shrinkage and swelling with seasonal
moisture fluctuations.
• Identification and understanding of these soils are required to safeguard
the existing and future constructions.
• Similarly differential movement of foundations of structures is a common
problem in problematic soil, due to changes in moisture content of soil
below the foundation.

11. CLASSIFICATION OF GROUND IMPROVEMENT METHODS

12. 1.Mechanical Modification:
• DensificationTechniques
• Increase of soil density by the application of short term external mechanical
forces
• Compaction of surface layers - by static, vibratory or impact rollers and
plate vibrators
• Deep compaction - by heavy tamping at the surface or vibration at depth

13. 2. Hydraulic Modification:
• Free pore water is forced out of soil via drains or wells.
• Coarse grained soils - by lowering the ground water level through pumping
from boreholes, or trenches.
• In fine grained soils - long term application of external loads (preloading) or
electrical forces (electro-kinetic stabilization)
• E.g.: Preloaded vertical drains - vertical drains accelerate the consolidation
process

14. 3. Modification by inclusions and
confinement:
• Reinforcement techniques introduce discrete inclusions that stiffen and
strengthen a soil deposit.The high stiffness and strength of the inclusions
also tend to reduce the stresses imposed on the weaker materials between
the inclusion.
• e.g. Reinforcement by fibers, strips, bars, meshes and fabrics (geo
synthetics like geotextiles) imparts tensile strength to a constructed soil
mass.
• In-situ reinforcement is achieved by nails and anchors.
• Stable earth retaining structures can also be formed by confining soil with
concrete, Steel, or fabric elements

15. 4. Physical and chemical modification
(Stabilization technique)
• Stabilization by physically mixing additives with surface layers or columns
of soil at depth – Additives includes natural soils, industrial by-products or
waste materials and cementitious and other chemicals which react with
each other and/or the ground
• e.g.: Usage of admixtures like cement stabilization
• Soil stabilization by heating the ground (evaporates water and causes
permanent change in soil structure)and by freezing the ground (solidifies
part or all of the water and bonds individual particles together) - thermal
methods of modifications.

16. DIFFERENT TYPES OF PROBLEMATIC SOILS

17. 1. Expansive soil
• Expansive soils contain minerals such as smectite clays that are capable of
absorbing water and increase in volume.
• Exert enough force on a building or other structure to cause damage.
• Shrinks when they dry out.
• This shrinkage can remove support from buildings
or other structures.
• e.g. Black cotton soil

18. 2. Collapsible soil
• Collapsible soils are those unsaturated soils that can withstand relatively
high pressure.
• Upon wetting they are susceptible to a large and sudden reduction in
volume.
• e.g. Pure gravel

19. 3. Soft soil
• Water content of the soil is very high.Thus modification is required to
reduce water content.
• e.g. Marine clay, Peat
4. Organic soil
• Construction over organic soils has historically been a problem due to the
typically low strength and high compressibility that is common to these
materials.

20. 5. Karst deposit
• Soils are formed by the distribution of soluble rock like limestone, gypsum,
etc.
• They have very less density.

21. Solutions & alternatives
• Avoid the particular site.
• Design the construction accordingly.
• Design the planned structure accordingly- Flexible or rigid structure.
• Remove and replace unsuitable soils. Removing organic topsoil, which is
soft, compressible, and volumetrically unstable.
• Attempt to modify the existing ground.
• Enable cost effective foundation design.

22. SELECTION OF SUITABLE GROUND
IMPROVEMENT BASED ON SOIL CONDITION

23. METHOD SOIL CONDITION
Soil removal and replacement Soft or weak soil
Soil displacement Very soft soil
Trenching technique Soft, fine grain soils, hydraulic fills
Preloading technique NC, FGS, organic soils and fills
Preloading with vertical drain NC, FGS, organic soils and fills
Electro-osmosis NC clay and silty clay
Dynamic Compaction Cohesionless soil above ground water
(weak soil)

24. METHOD SOIL CONDITION
Vibro Replacement Soft Cohesive soil
Vibro Displacement Stiffer Cohesive soil
Vibro Compaction Cohesionless soil with less than 30%
fines, up to 30m
Grouting (Deep mixing) CGS and FGS upto 52m
Heating Cohesive Soil
Freezing Soil belowWT and cohesive soil above
WT
Filler All soils

25. METHOD SOIL CONDITION
Reinforcement Soft Soils
Lime Stabilisation Sandy Soil
Cement Stabilization Pulverized Soil

26. EMERGING TRENDS IN GROUND
IMPROVEMENT TECHNIQUES

27. • Environmental geo-technics and Solids
• Waste management using ground improvement
• Containment and constructive use ofWaste material
• Low cost technologies with soil and additive
• Geo-synthetics
• Bio technical stabilization
• Development of New machinery ,particularly for deep compaction
• Availability of New construction materials such as Geofoams, geo-
composites

28. Types of Geosynthetics
• Geotextiles
• Geogrids
• Geonets
• Geocomposite
• Cellular confinement system

29. 1.Geotextiles
• Geotextile polymer is made from Polyester or polypropylene take into
account to be strong and very durable .
• They are two types of Geotextiles
• They are woven and non-woven geotextiles.

30. 2. Geogrids
• Geogrids are plastic formed into a very open netlike form
• Made from knitting the polypropylene
• There are 2 types of Geogrids .
• Uniaxial and biaxial geogrids

31. 3. Geonets
• Geonets are all made of polyethylene
• Molted polymer is pushed out through slits in opposite rotating –dies which
forms a matrix or a net.
Fig.Geonet

32. 4. Geocomposite
• The basic philosophy behind geocomposite material is to combine the best
feature of different material in such a way that specific application are
addressed in the optimal manner and at minimum cost.
Fig. Geocomposite

33. 5. Cellular confinement system
• Also known as geocells.
• Are widely uses in construction for erosion control, soil stabilization on flat
ground and steep slopes, earth retention etc.
• 3-D honey comb like structure made full with
land grest stone and building material made
of small stone, sand and cement.
Fig. Geocells

34. DIFFERENT MATERIALS USED FOR GROUND
IMPROVEMENT AND ITS PROPERTY

35. 1. BITUMINOUS STABILIZATION
• Asphalts, tars and pitches are used in various consistences
• Mixed with cohesive soils, bituminous materials improve the bearing
capacity and soil strength at low moisture content.
• Purpose of incorporating bitumen into soils is to maintain low moisture
content.

36. 2. CHEMICAL STABILIZATION
• With calcium chloride
• With sodium silicate
• With gypsum
Chemical stabilization with calcium chlorate – calcium chloride being
hygroscopic and deliquescent is used as a retentive additive in mechanically
stabilized soil bases and surfacing.The vapor pressure gets lowered, surface
tension increases and rate of evaporation decreases.The freezing point of
pure water gets lowewd and it results in prevention or reduction of
frostheave.

37. Chemical stabilization with sodium silicate- used in combination with other
chemicals such as calcium chloride, polymers, chrome lignin, alkyl
chlorosilanes, siliconites, amines and quaternary ammonium salts, sodium
hexametaphosphate, phosphoric acid combined with a wetting agent.

38. 3. USE OF INDUSTRIALWASTES
• Utilization of industrial wastes such as rice husk ash and fly ash for soil
improvement is a sustainable and cost-effective technique.
• Geotechnical properties includes index properties like liquid limit, plastic
limit, and differential free swell index and engineering properties like
compaction and strength characteristics of soil are greatly improved using
the industrial waste materials like Rice husk ash, fly ash.

39. 4. MECHANICAL STABILIZATION
• Compaction
• Soil reinforcement
• Addition of graded aggregate materials
• Mechanical remediation-This is the technique where contaminated soil is
physically removed and relocated to a designated hazardous waste facility
far from centers of human population. In recent times, chemical and
bioremediation have proven to be a better solution both economically and
environmentally.

40. BRIEF INTRODUCTION TO SUSTAINABLE
METHOD OF GROUND IMPROVEMENT

41. • GI using bio-chemical techniques
• Biotechnical Methods
• Use of Plants to prevent erosion
• Use of natural materials like bamboo and timber
• Soil improvement with calcium phosphate compound (CPC)
• Soil improvement with microbially induced calcite precipitation (MICP)

42. MICROBIAL METHODS

43. • Microbiological process is more environmentally friendly than other
conventional treatment methods.
• The bacteria’s or microbes found in around are used in the process.
• The process involved in microbial effect results in the pores of the soil
matrix.
• The formation of mineral precipitate in pores alters the soil properties by
cementation called bio-cementation.
• The other way is process of filling voids by a product resulting from
microbial induced biochemical process called as bio-clogging.
• Each of the process applied results in influencing different geotechnical
properties of soil.

44. MICROBIOLOGICAL MECHANISM
• The mechanisms for microbiological applications to geotechnical
engineering can be divided into two main categories: bioclogging and bio-
cementation.
• Bioclogging is a process where the soil void is filled by the product from
microbial induced biochemical process.
• Biocementation is to enhance the strength and stiffness properties of soil
and rocks by introducing bacteria and cementation reagents into the soil.
• Bioclogging includes formation of impermeable layer of algal and cyano
bacterial biomass

45. • Biocementation includes binding of the soil particles with sulphides of
metals produced by sulphate reducing bacteria and binding of the particles
with carbonates of metals produced due to hydrolysis of urea. Binding of
the particles with ferrous and ferric salts and hydroxides are produced due
to activity of iron-reducing bacteria

46. APPLICATIONS OF MICROBIAL IN
GEOTECHNICAL ENGINEERING
• Reinforcing or stabilizing soil to facilitate the stability of tunnels or
underground constructions;.
• Increasing the bearing capacity of piled or non-piled foundations.
• Reducing the liquefaction potential of soil.
• Treating pavement surface.
• Strengthening tailings dams to prevent erosion and slope failure.
• Binding of the dust particles on exposed surfaces to reduce dust
levels.

47. • Increasing the resistance of offshore structures to erosion of
sediment within or beneath gravity foundations and pipelines
• Stabilizing pollutants from soil by the binding
• Controlling erosion in coastal area and rivers