Foundation, Concrete and Earthquake Engineering

What is the Long Column Behavior of Pile Foundation?

Dear reader we have published about classification of piles based on load transmission mechanism and real situation in this load transmission. Here we will discuss about the error in assumption regarding point bearing pile penetrating through soft loose deposit.

We know that some piles derive support from point bearing stratum. There have a wrong consideration that piles are in free standing column condition when they are surrounded by soft soil even in fairly stiff soil. We know that such a long member have every risk of buckling when they are loaded axially.

Buckling of pile foundation during earthquake generated liquefaction
But from theory and experience as well clearly produce that there have no possibility of buckling even that are surrounded by very soft soil which were erroneously considered to be buckled under axial loads. When some lateral components of load come in addition to axial loads, the consideration have to be modified. But in this post we will not discuss about lateral component. In the upcoming posts we will discuss about design consideration for piles subjected to both axial and lateral forces and design procedures for piles subjected to both axial and lateral forces.

Now, designer limits working stress in materials of piles under direct compression by providing sufficient section and reinforcement in case of concrete pile and choosing a suitable method of drilling or driving. We know some piles are made to tapper to their tip with the gaining of depth. In such piles, obviously, the tip section is critical section to be checked. In the previous post we have discussed about working stress limitation and recommended slump for concrete pile construction. Once designer ensured that the tips are not failed in overstressing, the capacities of piles that derive main support form end bearing depend on surrounding soil materials. In the next post we will discuss how an end bearing pile can be used to have some skin resistance too.

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