Water During Piling ?
Often we encounter water during piling pipe.This is sub soil water which seeps through when the piling is in progress.As such water is not harmful ,but it loosens the adjoining soil which collapses inside the Pile hole .In such cases, there are two methods to manage the progress of Piling:
Option 01: Casing pipe:
A casing pile of adequate diameter is inserted into the Pile Hole which retains the soil.There are practical limitations to casing pipe since it is difficult to procure the exact diameter of the mild steel casing pipe at a short notice and secondly, it is again difficult to retrieve the pipe from its position after the pile hole is completed.
Option 02: Bentonite slurry.
Bentonite is a chemical powder which stabilizes the cohesive soil.Bentonite powder is just poured inside the pile hole. This mixes with the water and forms a protective layer on inner surface.
Use of Tremie:
The concreting in the Piles offers a special challenge.Unlike the columns, the concrete cannot be simply poured from the top of the pile .Because if the concrete is dropped from a height of more than 2.5 meters, it shall result into ” segregation . Segregation happens when sand & aggregate get disengaged from a common bond. the concrete looses its strength.
In such cases, a Tremie is convenient. it is a big size metallic funnel which receives the concrete. There is a long mild steel pipe connected to the funnel. the concrete smoothly travels from the funnel to the pipe and gets slowly deposited on the bottom of the pile shaft. the pipe is lifted slowly as the concrete work progresses upwards.
Precautions during Piling :
In case of Piles there is a safety hazard of someone falling in the freshly dug pile shaft.Even in hand augured ,Under-reamed piles, there are cases where a child has fell inside . Due to the small diameter, the rescue is very difficult. Therefore ,it is advisable to follow a policy of ” Dig & cast“. So, when boring of first pile is complete , immediately put the reinforcement cage inside it and begin the Pile casting. Start a second piling only after the concreting is completed.If due to rains or some other reason , it is not possible to do concreting , then it must be made compulsory that the Pile hole be covered with strong plates.
