ESSEN PILING DIVISION
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Essen Piling Division
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PILE FOUNDATIONS
A) What is Piling?
Piling is a deep foundation, used to transfer the load at desired depth either by end bearing or skin friction. Foundation is described as piled when the depth is three times the breadth. Piling works by inserting vertical columns of concrete, steel or wood are driven deep into the ground.
B) When to adopt Pile Foundation?
Following are the situations when pile foundation system can be adopted:
- Ground water table is high
- Heavy and uniform loads from superstructure are imposed
- Other types of foundations are costlier or not feasible
- When the soil located at a shallow depth is compressible
- When there is the possibility of scouring, due to its location near river bed or sea shore, etc
- When soil excavation is not possible up to desired depth due to poor soil conditions
Soil Investigation is the first step involved in piling
C) What is Soil Investigation?
Soil Investigation, also known as Geotechnical investigation is the process of gathering information, within practical limits about the stratification (layers) and engineering properties of the soils underlying the proposed construction site.
This procedure is done with the aim of establishing whether soil is safe and solid for construction.
Methods of Soil investigation:
- Standard Penetration Test: This test measures the resistances of the soil to the penetration of the split spoon sampler driven into the bottom of the bore hole. This test establishes the relative density of the soil
- Cone Penetration test: It is performed using an instrumented probe with a conical tip, pushed into the soil hydraulically at a constant rate. A basic CPT instrument reports tip resistance and shear resistance along the cylindrical barrel.
- Vane Test: It measures the shear strength of soft cohesive soil. The steel vane is pushed into the soft clay soil and rotated by hand at a constant rate.
Methods of Piling
- Rotary-bored piling:It can be used to support any structure where high load-caring capacity is required. Rotary bored piling (RBP) uses a machine with specially designed drilling tools, buckets and grabs to remove soil and rock. With every four or five turns of flight, the auger is bored into the ground, withdrawn, and the soil removed until the design depth is reached.
- Conventional Bored Piling:Conventional bored pile (CBP) is a type of reinforced concrete pile which is used for high rise buildings which have heavy vertical load. Bored pile is a cast in-situ for which conventional rigs are used.
Types of Pile Foundations
- End Bearing Piles: End bearing piles are driven till the hard strata of the soil is achieved. The bottom end of the pile rests on a layer of especially strong soil or rock. The load of the building is transferred through the pile onto the strong layer.
- Friction Piles: Friction piles are used when the soil has weak load-bearing capacity for which the friction of pile surface with the soil is used to bear the load of the structure.
D) What is a Piling Rig?
Piling Rig: A piling rig is a construction machine that is used for piling in foundation. It is mainly applied to drill in sandy soil, clay, silty clay, etc and widely for foundation reinforcement, diaphragm walls and other foundation projects.
Essen group employs around 25 conventional rigs.
Types of Pile Foundation Tests
- Low Strain Integrity Tests: Low strain pile integrity test is a popular non-destructive test method to examine the piles for a uniform cross-section and/ or detect flaws like voids, cracks, length etc.
- High Strain Dynamic Pile Load Test: Dynamic load test is a quick method to evaluate the bearing capacity of a pile for loads similar to design loads. It can be used for pre-fabricated piles, cast in-situ piles, steel piles or wooden piles.
E) How is Pile Foundation Test conducted?
Conducting the tests for Pile Foundation involve dropping an impact ram/ drop hammer onto the specially designed pile head. The generated compression waves travels down the pile and are reflected from the pile toe upwards. The response of the reflected waves is captured through the sensors placed at the pile head. The reflected waves contain information about the shaft friction, toe resistance and pile defects.