BORED CAST IN SITU PILE

Tractor Mounted Hydraulic Rotary Rig (Direct Mud Circulation Method)

The system is very useful in congested areas where noise is prohibited.
Here the bored cast in situ pile is made by drilling the ground using a Tractor Mounted Hydraulic Rotary rig.
The boring is done with the raimmer which has provision for sending bentonite solution under pressure.
The bored muck is carried to the sur face by the circulating bentonite (So it is called direct mud circulation system) Once the hard strata is reached socketing will be done if required.
The stratum for termination is identified by conducting Standard Penetration Test.
Once the boring is complete the borehole is washed by circulating fresh water continuously.
The specific gravity of the out flow solution is measured using hydrometer to ensure that the bore is properly cleaned.
Then the reinforcement is lowered followed by tremmie and the concreting is done

Hydraulic Rotary Rig

The boring is done with soil auger for ordinary soils and for hard strata rock auger will be used.
The boring will be carried out with a huge suction force and the bentonite solution will be directly pumped in to the bore hole to prevent the collapse.
The stratum for termination is identified by conducting Standard Penetration Test.
Then fabricated reinforcement will be inserted in to the bore hole.
Once the boring is complete the borehole is washed by circulating fresh water continuously.
The specific gravity of the out flow solution is measured using hydrometer to ensure that the bore is properly cleaned.
Then the concreting will be done by tremmie method.

DRIVEN CAST IN-SITU PILE

MAX DIA 600MM [ IS 2911 PART(1) SEC(1) ]

Driven piles are installed by driving a casing pipe.
The soil investigation reports are based on the N-value.
The casing pipe is driven by single acting drop hammer with the required height of fall.
This is determined by the state of compaction of the soil strata.
Soil investigation report based on the N-value also decides this.
Casing reaches the hard strata beyond which the rate of penetration is very small, concrete is poured with the help of chute cart, and the casing is extracted progressively, simultaneously tamping the tube as the tube is extracted

As the name suggests, driven cast in situ piles are installed by driving a casing pipe whose outer diameter represents the nominal diameter of the pile. The casing pipe is driven by a single-acting drop hammer with the required height of fall determined by the state of compaction of the soil strata. This is obtained from the soil investigation report based on the N-value. Once the casing reaches the hard strata beyond which the rate of penetration is very small (This is termed as set. The set is defined as the penetration for a given number of blows; say for example this can be 10mm for the final 10 blows) concrete is poured with the help of chute cart, and the casing is extracted progressively, simultaneously tamping the tube as the tube is extracted.

The three main advantages are:

The state of compaction is assessed as the tube is driven by observing the number of blows required for a constant depth of penetration
The energy imparted to the soil by driving the tube compacts the surrounding soil which helps in the increase of friction capacity of the pile
The tamping of the tube while extraction creates serrations in the pile shaft which ensures the mobilization of the shaft friction.