Foundation, Concrete and Earthquake Engineering

What is Piling? What is Point of Refusal?

Piling is portion of system of foundation that is pushed into just under the cap into the earth to provide support to the superstructure above. Piling is used in relatively weak shallow strata of the earth where loads from superstructure are transferred through piles to deeper stronger strata. It is often used as foundation repair solution for existing distressed building where foundation sinking, cracking and warping in different structural member are visible, alarming the dwellers of structural failure. The names that are used regarding piles depending on types and uses of them in Geotechnical engineers are :

a. Segmented piling

b. Push piling

c. Pile blocks

d. Steel piling 

Driving pile to point of refusal
e. Concrete piling

f. Double piling

There have other name like grouted pile and drilled pile and different languages and regions of the world also named piles in hundred ways.

In case of piling in sandy soils, friction developed around surface of the piles developed main capacity to the piles. In case of piling in clay soil, the capacity of piles are expected to develop from both wall friction between soil and pile surface and
capacity that developed at the tip of pile (end bearing) in a more stable or competent stratum.

Pile Point of Refusal:

This is a point at which level piling operation can no longer be continued into the earth without lifting or breaking the structure above. A lighter structure, as it has less weight, it reaches point of refusal at a relatively shallow depth. A heavy structure, as it is relatively heavier, it attains its refusal point at relatively deeper point so that it reach hard strata or rocks or it have combined or isolated action of   skin friction enough to support heavier loads. It should be noticed that a point of refusal in wet condition is not the same as it in dry condition.

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