This document discusses various methods for soil improvement applied to foundations and slopes. It describes 11 different soil improvement methods: 1) compaction, 2) mechanical stabilization using admixtures like lime and cement, 3) preloading, 4) vertical drains, 5) dewatering, 6) electro-osmosis, 7) dynamic compaction, 8) stone columns, 9) grouting, 10) soil reinforcement using geosynthetics, and 11) using waste materials. For each method, it provides details on the process, materials used, and effectiveness in improving soil properties like bearing capacity, shear strength, and consolidation. The overall purpose of soil improvement is to develop stable foundations and slopes for structures.

2. The design of a structure which is economical and safe to construct, is durable and has low
maintenance costs. All constructions systems are built either on earth, in earth, and/or with
earth. The stability of the foundation of a building, a bridge, an embankment or any other
structure built on soil depends on the strength and compressibility characteristics of the subsoil.
The terms soil improvement,
ground modification and ground improvement
are used interchangeably. A number
of foundation and slope treatment alternatives
are possible, and the choice of the most
appropriate method or methods depends on
the soil types involved, whether predominately
granular or cohesive, and the type, function and
performance requirements of the facility. In recent years, the interest in soil improvement
techniques for foundations and
slopes has greatly increased, primarily due to
the world-wide increase in the cost of land
together with an increase in environmental

3. Five major functions of soil improvement applied to foundations and slopes:
• increasing bearing capacity;
• controlling deformations and accelerating consolidation;
• providing lateral stability for slopes and excavations;
• seepage cut-off and other types of environmental control; and
• increasing resistance to liquefaction of loose, saturated granular deposits.
The methods of soil improvement are:-
1. Compaction.
2. Mechanical stabilization by Use of Admixtures.
3. Preloading.
4. Vertical drain.

4. 5. Dewatering.
6. Electro-Osmosis.
7. Dynamic compaction.
8. Stone columns.
9. Grouting.
10. Reinforcement the soil by Geosynthetics.
11. Using waste materials.

5. 1. Compaction:
Soil compaction is the densification or reduction in void ratio of a soil through the
expulsion of air by the application of the mechanical energy.
Soil compaction is extensively employed in the construction of embankments and in
strengthening the subgrades of roads and runways.
2. Mechanical stabilization by Use of Admixtures
The physical properties of soils can often economically be improved by the use of
admixtures. Some of the more widely used admixtures include lime, Portland cement and
asphalt.
The process of soil stabilization first involves mixing with the soil a suitable additive which
changes its property and then compacting the admixture suitably. This method is applicable only
for soils in shallow foundations or the base courses of roads, airfield pavements, etc.
Soil-lime Stabilization
Lime stabilization improves the strength, stiffness and durability of fine grained materials.
In addition, lime is sometimes used to improve the properties of the fine grained fraction of
granular soils. Lime has been used as a stabilizer for soils in the base courses of pavement

6. Soil-Cement Stabilization
Soil-cement is the reaction product of an intimate mixture of pulverized soil and
measured amounts of Portland cement and water, compacted to high density. As the cement
hydrates, the mixture becomes a hard, durable structural material. Hardened soil-cement has the
capacity to bridge over local weak points in a subgrade. When properly made, it does not soften
when exposed to wetting and drying, or freezing and thawing cycles.
Bituminous Soil Stabilization
Bituminous materials such as asphalts, tars, and pitches are used in various consistencies
to improve the engineering properties of soils. Mixed with cohesive soils, bituminous materials
improve the bearing capacity and soil strength at low moisture content.
3. Preloading:
Preloading is a technique that can successfully be used to densify soft to very soft
cohesive soils. Large-scale construction sites composed of weak silts and clays or organic
materials (particularly marine deposits), sanitary land fills, and other compressible soils may
often be stabilized effectively and economically by preload.

7. 4. Vertical drain:
Vertical drains are normally used for consolidating very soft clay, silt and other
compressible materials as following
1. It consists of a series of vertical sand drains or piles. Normally medium to coarse sand is
used.
2. The diameter of the drains are generally not less than 30 cm and the drains are placed in a
square grid pattern at distances of 2 to 3 meters apart. Economy requires a careful study of the
effect of spacing the sand drains on the rate of consolidation.
3. Depth of the vertical drains should extend up to the thickness of the compressible stratum.
4. A horizontal blanket of free draining sand should be placed on the top of the stratum and the
thickness of this may be up to a meter, and
5. Soil surcharge in the form of an embankment is constructed on top of the sand blanket in
stages
5. Dewatering:
Dewatering is a technique of soil improvement whereby the amount and/or pressure of
pore water is reduced .Dewatering usually causes densification.

8. 6. Electro-Osmosis:
Electro-osmosis can be used to stabilize unstable
sand and silt, coarse-fine silt and clays the application of a direct current (D.C.) potential across
an anode and a cathode causes the pore water and part of the boundary film of water that is
attached to the soil particles to move to the cathode. This action directs the seepage pressures
from the anode to the cathode, increases the effective stress in the soil, reduces the water
content of the soil and causes a chemical exchange that strengthens the soil.
7. Dynamic compaction:
Dynamic compaction is carried out by repeatedly impacting the ground surface by
dropping a pounder from a given height from a heavy duty crane at a rate of one blow every 1–3
minutes. Usually the blows are concentrated at specific locations, the distances between the
centers of impact frequently ranging between 4 and 20 m.
8. Stone columns:
Stone columns have particular application in soft inorganic, cohesive soils and are
generally inserted on a volume displacement basis. The size of the stones used for this purpose
range from about 6 to 40 mm.

9. 9. Grouting:
Grouting usually refers to the injection of suspensions, solutions and emulsions into pores
in soils to improve their geotechnical characteristics. Particulate grouts consist of cement-water,
clay-water or cement-clay water mixes. Grout used to reduce the permeability of the ground
must be able to develop sufficient strength to withstand the hydraulic gradient imposed.

10. Reinforcement the soil by Geosynthetics:
Reinforced earth is a composite material consisting of soil containing reinforcing elements
which generally comprise strips of galvanized steel or plastic geogrids. In situ reinforcement is the
inclusion of resistant elements in the moving soil mass in order to improve its shearing
resistance.
Geosynthetics Types
In general, there are nine types of geosynthetics: Geotextiles, Geogrids, Geonets,
Geomembranes, Geopipes, Geocells, Geofoam, Geocomposites and Geosynthetic clay liners.

13. CBR value for the crest point increased more than
three times when compared with unreinforced soil.

14. Gypseous Soil for all samples the use of geogrid reinforcement increase the
value of California Bearing Ratio (CBR), CBR value for the optimum point increased
almost two times when compared with unreinforced soil. The position of first layer
of geogrid under the surface have a large influence on CBR, the position 0.15D gives
a higher value of CBR for all samples, therefore it can be say that the reliable depth
is 0.15D where D is the diameter of CBR mold.

15. 11. Using waste materials:
Using CKD as Lining
1. Granular Materials the CBR
value of the granular material
increased with increasing the
depth of CKD lining layer until the
optimum position which were
0.2H from the top of the subbase
layer. Moreover, CBR value for the
optimum point increased almost
three times when compared with
untreated material.

16. 2. Sand
There are obvious increases
in shear strength in stabilized
soil with CKD in all four cases
of study. The higher results
obtained in case of CKD lining
at depth of 0.5B.
The angle of internal friction
φ increased by using CKD
lining. The higher value of φ
happened in soil samples
with CKD lining at depth of
0.5B. In this situation, φ equal
to 42.77°, and the increase in
it to the φ in soil without CKD
is about 2.14 times.