One of the most acceptable methods to design a laterally-loaded shaft is the P-y curve approach. In order to develop P-y curves in soft weathered rock, four complementary approaches have been followed. One is the Finite Element method of modeling using a computer program called ABAQUS for 3-dimensional analytical modeling of resistance forms. The second is laboratory work to model the characteristics of P-y curves in the soft weathered rock. The third is field testing using full-scale shafts to develop and verify P-y curves in the soft weathered rock. Finally, Class A performance predictions are calculated using the development of the model.
This research reveals that none of the current proposed P-y curve approaches to design-drilled shafts embedded in soft weathered Piedmont rock profile can reasonably estimate the load-versus-deflection characteristics of a laterally loaded shaft.
A new concept of the point of rotation has been developed based on measured profiles from field and laboratory tests, and F.E.M. analysis to define the load-deflection characteristics of drilled shaft embedded in soft weathered rock. A method to evaluate stiffness properties of the soft weathered rock by utilization of the in-situ testing device, the rock dilatometer, as well as a method based on the information of joint conditions, RQD, and the strength properties of cored samples are proposed.
The proposed P-y curve model for soft-weathered rock closely agrees with field test results, which are performed in various rock profiles, and also the proposed method is verified by comparisons with published test results.