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Stone Columns

  The installation of stone columns is one of the most widely-used ground improvement methods in the world. This technique consists in installing and compacting a pile of stones into the ground, following a grid pattern previously determined by a test trial.

Stone columns soil treatments have different benefits:
  • Global improvement in soil characteristics
  • Increase in soil bearing capacity
  • Decrease in soil settlement under load
  • Speed up of vertical drainage
  • Stability of embankments
  • Reduce of risk liquefaction in seismic areas
 

 

Bottom & Top
Feed system 

There are two methods to produce stone columns and they differ mainly in the system that is used to release the stones into the ground:

The Bottom Feed System: The stones are released at the bottom of the stone column hole through a special stone pipe adapted to the Vibrolance poker. 

The Top Feed System
: The stones are released from the ground level into the hole created by the vibrolance.
 

 

STONE COLUMNS USING THE "BOTTOM FEED SYSTEM" (BFS)

The BFS system controls the length and the diameter of the stone column, better than the Top feed system. In addition,  there is no risk of soil collapse while the stone is released, because the Vibrolance is not withdrawn from the ground until the stone column is finished.  Thus, the BFS system allows the contractor to have a continous production process that results in higher productivity and time savings.

Stone-column-rig-PTC-3Stone Column rig ground improvement PTC
To see PTC Stone Column Rig: SC13
                          

1. Preparation:
The skip is charge with stone and then it travels up the leader and automatically discharges the stone into the upper tank. Pressurised air pushes the stone throught the feeding tube down to the Vibrator tip.

2. Penetration:
PTC Vibrolance penetrates the ground under the action of its own weight and the lateral vibrations emitted at the poker, and assisted by the pull-down system of the rig.

3. Stone feeding & Compaction:
When the required depth is reached, the Vibrolance does a slight upward movement to create the space where the stone will be released. Pressurised air is blown through the pipe to push the stone into the ground.  Afterwards, the Vibrolance does downwards movements to compact the stones. This process is repeated at different dephts levels until the compacted stone column reaches the surface. The stone column rig is then repositioned to start another stone column.

 

STONE COLUMNS USING THE "TOP FEED SYSTEM"

Vibrolance stone column top feed systemVibrolance Deep compaction  Vibro-compaction PTC

  It is the most cost efficient ground improvement method. It requires the use of a free hanging vibrolance that penetrates the ground thanks to the lateral vibrations emitted by its poker. During penetration, the soil is laterally compacted by displacement allowing the vibrolance to create the hole that will contain the stone column.  

When the desire depth is reached, the vibrolance is withdrawn to allow the stones to be released from the ground surface into the hole. The stone release is done by stages to allow a better compaction of the entire stone column.   Each time the hole is filled with stones, the Vibrolance is driven back again to compact them.  This process is repeated several times until the stones reach the surface and a compacted stone column is formed.

Click here to see the product information about PTC Stone Column using Top Feed System