Pile Works Construction Method
Piles are available as either cast-in-place or precast driven piles.
The following steps are involved to develop cast-in-place piles:
- Hammer a thin-walled steel tube into the ground.
- Eliminate all soils departed inside the tube.
- Drop a steel reinforcement cage into the tube.
- Casting of the pile should be done by pouring wet concrete into the tube.
The thin walled steel tube is known as the casing, and it's purpose is build up a secure mould for casting concrete that does not contain any earth and debris. Once the casting is finished, it does carry out any structural role.
Some soils are extremely cohesive. It signifies that when a hole is bored into the soil like 1 foot wide by 50 feet deep, then the soil retains the shape of the hole and does not fall into the hole and block it. If such soil exists at the site, then it is not required to provide a casing in place: the casing can be applied to bore the hole for the pile, and then eliminate it, and then cast the pile in place. In this way, huge cost is saved since the similar casing tube is utilized to bore holes for all the piles.
These types of piles are initially cast at ground level and then hammered or pushed into the ground with a pile driver. It is a machine that retains the pile properly in vertical direction, and then hammers it into the ground blow by blow. Each blow is jammed by lifting a heavy weight and dropping it on the top of the pile - the pile is temporarily wrapped with a steel cap so that it can't be detached. Therefore, the pile driver accomplishes two functions - initially, it operates as a crane, and lifts the pile from a horizontal location on the ground and rotates it into the exact vertical location, and then, it hammers the pile down into the ground.
Piles should be hammered into the ground till refusal, at which point the piles can't be pushed any more into the soil.
While driving pile, huge noise is created and consequently extreme vibrations occurs through the soil. Hence, it becomes complicated to apply them in sensitive locations. The application of piles is restrained in residential areas in several countries. The vibrations also lead to structural damage to oldest buildings which are located nearby. Under such circumstances, it is suggested to utilize micropiling or helical piling as these do not require hammering.
Micropiles or minipiles belong to small piles which are built up as follows :
- A hole a little bigger than the pile diameter is created and the full length of the pile is dug into the ground with an equipment similar to a soil boring machine.
- A precast concrete pile is pushed or driven into the hole.
- A concrete grout is poured into the gap among the pile and the soil.
Helical piles stand for steel tubes which contain helical (spiral) blades affixed to them. These are bored into the ground, implying that the pile operates as a giant drill bit, and is rotated and driven into the ground from above. Once the steel pile is pushed into the ground, a pile cap is poured on top of the pile to make it ready for the construction above.