Mechanical stabilization of soil

GROUND IMPROVEMENT TECHNIQUES(MECHANICAL STABILIZATION) : 

GROUND IMPROVEMENT TECHNIQUES(MECHANICAL STABILIZATION) By Ankit M. Asher

GROUND IMPROVEMENT TECHNIQUES : 

GROUND IMPROVEMENT TECHNIQUES GROUND IMPROVEMENT TECHNIQUES 2 Process of improving the engineering properties of the soil and thus making it more stable . Uses To reduce permeability To reduce compressibility foundation/sub base To increase shear strength To increase bearing capacity Significance The principle of soil stabilization are used for controlling the grading of soil and aggregates in the construction of bases and sub bases of highways.

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GROUND IMPROVEMENT TECHNIQUES 4 MECHANICAL STABILISATION ( GRANULAR STABILISATION ) The process of improving the properties of soil by changing its gradation. Two or more types of natural soils are mixed to obtain a composite material which is superior to any of its components ( i.e. Aggregates and binders )

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GROUND IMPROVEMENT TECHNIQUES 5 Factors affecting mechanical stability of soil Mechanical strength of aggregate : The mixed soil is of greater strength if the aggregates have high strength. Mineral composition : the stability of soil largely depends on composition of minerals. Gradation : Voids of coarser particles to be filled with finer particles.

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GROUND IMPROVEMENT TECHNIQUES 7 PRINCIPLE : The compaction process consists of a flotation of the soil particles as a result of vibration, which then allows for a rearrangement of the particles into a denser state.

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EFFECTS : The ratio of horizontal to vertical effective stress is increased significantly.• The permeability of the soil is reduced 2 to 10 fold, depending on many factors.• Enforced settlements of the compacted soil mass are in the range of 2 % to 15 %, typically 5 %• The stiffness modulus can be increased 2 to 4 fold.

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Standard Penetration Test or Cone Penetration Test1)  The number of blows per each foot or cone resistance of soil sample driven by the sampler will be recorded and the Engineer will determine the test interval. 2) Tests shall be terminated at 2 foot below the specified soil improvement depth.

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GROUND IMPROVEMENT TECHNIQUES 11 DYNAMIC COMPACTION Dynamic compaction is a method that is used to increase the density of the soil by dropping a heavy weight repeatedly on the ground at regularly spaced intervals. The weight that is used, depends on the degree of compaction desired and is between 8 tonne to 36 tonne. The height varies from 1m to 30m.

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GROUND IMPROVEMENT TECHNIQUES 12 RAPID IMPACT COMPACTION It uses a 7.5-ton weight that is dropped as much as 60 times per minute to compact soft areas for increasing bearing capacity, minimizing settlement and providing uniform support

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GROUND IMPROVEMENT TECHNIQUES 13 References : www.geostructures.com www.wikipedia.org www.youtube.com www.vibroflotation.com Soil mechanics and foundation engineering by K. Arora , third edition, 1992

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