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What is stone columns? Why it is required?It is a technique adopted for the soil which didn’t have the sufficient characteristics to permit construction. The stone column technique, also known as vibro-replacement or vibro-displacement, is a ground improvement process where vertical columns of compacted aggregate are formed through the soils to be improved. Stone columns, also known as granular piles, consist of stone aggregates compacted into a vertical hole. Generally, the size of aggregate used is 20mm to 75mm and the depth of hole is about 15m to 20m with the diameter of 0.6m to 1.0m. The compaction is achieved by a vibrating probe or by ramming.
Uses Of Stone Columns:
- Increases the shear strength.
- Lowers the compressibility of the composite soil consisting of the stone column and the surrounding soil
Priebe’s Method of Stone Columns Design:The design of stone columns by Priebe’s method, mainly involves the following steps
- Determination of basic improvement factor.
- Determination of the improvement factors by considering, column compressibility and overburden pressure.
- Finding the compatibility controls.
- Determination of the shear values of improved ground.
- The column is based on a rigid layer
- The column material is uncompressible
- The bulk density of column and soil is neglected