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Sand compaction piles are one of the essential ways for improving ground stability, controlling liquefaction, decreasing settlement, and similar uses. This method contains pushing a hollow steel pipe into the ground.
The bottom is sealed with a collapsible plate down to the needed depth and then the pipe is filled with sand. The pipe is removed while the air pressure is produced against the sand inside it.
The bottom plate was unsealed at the time of withdrawal and the sand back filled the voids made earlier during the pushing of the pipe. The sand backfill contains the soil surrounding the compaction pipe from collapsing as the pipe is removed. During this method, the soil reaches densified.
But the vibro-hammer employed in this method has a negative effect in the form of vibration and noise on the surrounding environment which makes it challenging to employ this approach in urban areas or at locations near existing structures.
To neglect these issues, a system with a non-vibratory Sand compaction pile method was developed, which does not need impact or vibration on the driving device to dig into the ground.
The equipment includes majorly of a sand compaction pile driving device employ as a base machine and a pushed lifting or driving device with a rotary drive motor to rotate the casing pipe.
1. Non-Vibratory Sand Compaction Pile Method
The Non-vibratory Sand Compaction method is mentioned below:
a. Set the casing pipe to the predetermined place.
b. By operating the forced lifting or driving device, install the casing pipe into the ground while rotating.
c. The sand is fed through the upper hopper after the pipe has reached the required depth.
d. Casing pipe is pulled up which results in the sand being pressed out to the void by compressed air.
e. The casing is then extracted along with the compaction of the pressed-out sand pile so as to enlarge it.
f. Above procedure is repeated till the sand piles are formed on the ground surface.
2. Design of Sand Compaction of Pile
The design of Sand Compaction piles depends upon:
a. Stability of the sand column
b. Piles and soil are subjected to equal vertical deformation
3. Advantages of Sand Compaction Piles
The advantages of sand compaction piles are as follows:
a. The immediate benefit of these sand piles is that the sand used is often considerably cheaper when compared to other similar ground improvement techniques like stone columns.
b. Construction of the sand columns is extremely fast.
4. Disadvantages of Sand Compaction Piles
The disadvantages of sand compaction piles are as follows:
a. After creating the hole, it’s fully supported by a casing during construction that prevents the possibility of collapse.
b. Sand compaction piles have a low stiffness when compared to other methods.
c. Hence larger percentage of replacement of weak soil is required. These piles do not have sufficiently high permeability to function as effective vertical drains during earthquakes.
d. Sand compaction piles are a possible solution for strengthening previous embankment foundations found to be susceptible to liquefaction or impervious foundations susceptible to stability problems like during an earthquake.
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