Details of Sand Compaction Piles
Sand compaction piles are used to serve different purposes like making longevity of the ground better, restraining liquefaction, lessening settlement and related applications. Under this method, a hollow steel pipe is entered into the ground. The bottom is sealed with a compressible plate down to the desired depth and then pipe is filled with sand. The pipe is detached when the air pressure is conducted against the sand inside it.
The bottom plate opens throughout removal and the sand backfills the voids which are formed previously at the time of entering the pipe. The sand backfill resists the soil encircling the compaction pipe from falling down while removing the pipe. The soil becomes compact while the process is going on.
Two types of Sand compaction piles method are available based on the system provided. First one is vibratory system having vibro-hammer and the other one contains a non-vibratory system with forced lifting or driving device.
But the vibro-hammer applied in this method produces a negative impact with vibration and noise to the adjoining environment and so, this method can’t be applied in the urban areas or at locations near to subsisting structures.
To get rid of these issues, a system containing a non-vibratory Sand compaction pile method was created so that the driving is entered into the ground without any vibration. The device comprises of a sand compaction pile driving device that is applied as a base machine and a forced lifting or driving device having a rotary drive motor to rotate the casing pipe.
Non-vibratory Sand compaction method:
• Place the casing pipe to the prearranged place.
• By using the forced lifting or driving device, set the casing pipe into the ground while rotating.
• The sand is supplied through upper hopper once the pipe has attained the desired depth.
• Casing pipe is drawn up which account for the sand to be pressed out to the void with compressed air.
• The casing is then removed along with the compaction of the pressed out sand pile in order to expand it.
• Above method is reiterated unless the sand piles are produced to the ground surface.
Design of sand compaction piles is based on the following:
• Strength of the sand column
• Piles and soil are dependent on equal vertical deformation
Benefits and drawbacks of sand compaction piles: The main benefit is that the sand used is significantly inexpensive relating to other equivalent ground improvement methods like stone columns. The process is very fast for building up the sand columns.
Once the hole is created, it’s entirely supported by casing throughout construction that resists the chances of collapse.
Sand compaction piles contain a low stiffness with regard to other methods. So, greater percentage replacement of weak soil is necessary. There is not enough penetrability for the piles to perform as useful vertical drains throughout earthquakes.
Sand compaction piles are very effective for improving the strength of pervious embankment foundations prone to liquefaction or impervious foundations prone to stability problems during an earthquake.