Back Analysis of Static Pile Load Test for SPT-Based Pile Design: A Singapore Experience

Abstract

The Chin’s plot method is the most widely used method in Singapore to assess the ultimate skin friction and ending bearing separately based on static pile load test results. In this study, a large number of pile load tests for driven piles were back analyzed using the Chin’s plot method. The obtained data were examined in order to evaluate the appropriate design ranges for skin friction coefficient, Ks and end bearing coefficient Kb, which are the two key parameters for pile capacity estimation in design. It was revealed that, generally, the currently adopted design ranges were over-conservative for displacement piles. New design ranges and limits for Ks, Kb and unit end bearing, qb, were suggested, and their typical values for conventional designs were recommended. Further, the importance of pile load test in the design of piling foundation was emphasized. Whenever practicable the ultimate pile bearing capacity should be obtained from pile load tests, and all indirect estimations of pile capacity should be evaluated against the static load test results.