Evaluation of Ultimate Pile Compression Capacity from Static Pile Load Test Results

Abstract

The in-situ static pile load testing is often carried out on the test pile by applying 1.5 times to 2.5 times the design pile capacity. Due to practical and time constraints, it is not possible to always load and test the pile up to the failure. The load-settlement behavior of the pile during pile load testing under this loading often does not reach the ultimate pile capacity. Hence, in order to utilize the maximum available pile capacity in the design of pile foundations, an extrapolation of load-settlement data are required to evaluate the ultimate pile capacity. Various methods were proposed in the past by researchers such as Chin, Decourt, Davisson, De Beer, Brinch Hansen etc. to evaluate extrapolated ultimate pile capacity. These methods have been adopted in this paper to estimate ultimate pile capacity using load-settlement data of 23 nos. static pile load tests performed on driven piles and drilled shafts. The ultimate capacities evaluated from different methods have been discussed and compared with each other and with ultimate pile capacities for piles tested up to the failure. Based on this comparison, it has been observed that when the test load is high and close to the ultimate load limit, the accuracy in estimated ultimate load can be achieved by all the methods. However, study on piles tested under very less or partial load revealed the overestimation of ultimate pile load except for the Davisson method. Each method estimated different values of ultimate load under different test loads and no specific method can be recommended based on accuracy to evaluate the ultimate pile capacity.