Geotechnical Engineering

DHARM

SOIL STABILISATION 721

SUMMARY OF MAIN POINTS

1. ‘Soil stabilisation’ means treatment of a soil with the objective of improving its engineering
   properties. This may be done without any additives or with one or more additives.


2. Mechanical stabilisation involves rearrangement of particles and densification by compaction or
   by changing the gradation by addition or removal of some of the fractions.
   It may also include stabilisation by effecting drainage of the soil including the application of
   thermal or electrical gradient.


3. Cement stabilisation is one of the most widely used among the methods in which additives are
   used. The soil-cement, thus obtained, is used primarily as a base for pavements. Cohesive soils
   are most suited for this treatment, although finer grains need more cement.
   Bitumen stabilisation is also commonly used especially for granular soils. It may also be used for
   waterproofing of cohesive soils.


4. Chemical stabilisation involves a chemical as the primary additive. Lime and salt have been
   very commonly used. Lime modifies the plasticity characteristics of clays, and is also used as a
   secondary additive along with bitumen or cement.
   Natural and synthetic resins, lignin, chrome-lignin and certain aggregants and dispersants are
   also used as additives to soil.


5. Stabilisation by grouting or injection is also an important technique. Soil, cement, bitumen, or
   some chemicals may be used for grouting either soil or rock.


6. California Bearing Ratio (CBR) is an empirical concept which is used to indicate the strength of
   a subgrade soil. It is defined as the ratio of the load or pressure required to cause an arbitrary
   penetration under standard test conditions to that required by a standard crushed rock mate-
   rial. It may be determined in the laboratory or in-situ.
   It is used for the design of flexible pavements with the aid of design charts developed specifically
   for the purpose.

REFERENCES

1. Alam Singh: Soil Engineering in Theory and Practice, Asia Publishing House, Bombay, 1967.


2. R.A. Barron: Consolidation of Fine-grained Soils by Drain Wells, Transactions, ASCE, 1948.


3. A.A. Beles and I.I. Stanenlescu: Thermal Treatment as a Means of Improving the Stability of
   Earth Masses, Geotechnique, Dec., 1958.


4. Bharat Singh and Shamsher Prakash: Soil Mechanics and Foundation Engineering, Nem Chand
   Brothers, Roorkee, 4th ed., 1976.


5. L. Casagrande: Electro-osmotic Stabilisation of Soils, Journal of Boston Society of Civil Engi-
   neers, 1952.


6. L. Casagrande: Review of Past and Current Work on Electro-osmotic Stabilisation of Soils, Harvard
   Soil Mechanics Series, Dec., 1953.


7. J.B. Hansen: Developing a Set of C.B.R. Curves, U.S. Army Corps of Engineers, Instruction Report
   No. 4, 1959.


8. HMSO: Soil Mechanics for Road Engineers, Her Majesty’s Stationery Office, London, U.K., 1952.


9. HRB: Use of Soil-Cement Mixtures for Base Courses, HRB war-time problems, No. 7, Washing-
   ton, D.C., 1943.