Stone Column

Stone Column is a vertical shaft form by back filling compacted and crushed stone gravel or sand or moisture of these granular or material to form granular pile or 1. They are used for all types of planned structures including building, foundations, damns, tanks, towers, embankment, etc.

Purpose of Stone Column:

The purpose of stone column as a ground improvement technique is generally adopted in clayed soils and in soft cohesive soils having low bearing capacity.

The primary objective of these techniques is mainly to increase the bearing capacity of soil.

It also reduces post construction settlement.

This method has been mainly used to improve sub soil building embankments.

Stone Column usually has dia of 0.5 to 0.75m. They are spaced at about 1.5m to3m.

The gravel used for stone column has a size range of 6m to 40m.

Methods of Construction:

Bearing and Ramming Methods: Steps involved are:

Holes of required size are bored by using float bailer.

After boring is completed crushed stones are back filled inside the casting.

Casing is withdrawn at short pass and granular fill is compacted by rammers.

After that, add additional granular charge and repeat stages till full length of column.

Pre-assembled stone column:

Bearing is carried out to required depth or bentonite slurry to obtain stability of sides of bore holes.

Once the boring is completed granular fills are compacted in pre assembled cages and lowered into pre-bored hole for initial interval of 3m.

After lowering, the compaction is carried out as per rammed stone column.

Vibro- Floatation Methods:

The Vibrofloat is allowed to sink into the ground due to its own weight assisted by water or air as a flushing medium, up to the required depth.

The soil surrounding the vibrofloat is disturb or remolded by vibrofloat and the soften material can be removed by jetting water or compressed air.

In this process a bore hole of larger dia than the vibrofloat is formed,once the vibrofloat is formed the formed boreholes are backfilled with gravel.