Evaluation of ultimate pile capacity based on non-failed load tests: A case study of piles in Bangkok subsoil

This research proposes a new method to estimate the ultimate pile capacity from failure load tests and proof tests of piles in Bangkok subsoil. A large database of load-settlement curves from failure load tests is examined. Existing methods in the literature are evaluated and the results of which are compared with the proposed method, in terms of their accuracy and precision when applied to different types of piles in Bangkok subsoil. The results suggest that Davisson, Brinch-Hansen 90%, Van de Veen, and the proposed methods should be used to estimate the interpreted ultimate pile capacity from failure load tests. For proof tests, the proposed method should be used to estimate the extrapolated ultimate pile capacity. The applied factors of safety and their associated risk are analyzed. The proposed factors of safety for the proposed method are suggested and the resulting pile settlements under allowable loads are evaluated. The proposed method is applied to case histories of bored piles with tips in sand. The results indicate that the piles can be loaded additionally above their design allowable pile capacity. The amount of additional load depends on applied factor of safety which in turn depends on allowable settlement that can be accepted.