Rock-socketed drilled shaft foundations are commonly used to resist large axial and lateral loads applied to structures or as a means to stabilize an unstable slope with either marginal factor of safety or experiencing continuing slope movements. One of the widely used approaches for analyzing the response of drilled shafts under lateral loads is the p-y approach. Although there are past and ongoing research efforts to develop pertinent p-y criterion for the laterally loaded rock-socketed drilled shafts, most of these p-y curves were derived from basic assumptions that the rock mass behaves as an isotropic continuum. The assumption of isotropy may not be applicable to the rock mass with intrinsic anisotropy or the rock formation with distinguishing joints and bedding planes. Therefore, there is a need to develop a p-y curve criterion that can take into account the effects of rock anisotropy on the p-y curve of laterally loaded drilled shafts.
A hyperbolic non-linear p-y criterion for rock mass that exhibit distinguished transverse isotropy is developed in this study based on both theoretical derivations and numerical (finite element) parametric analysis results. Evaluations based on parametric study on full-scale lateral load test on fully instrumented drilled shaft have shown the insights on the influences of rock anisotropy on the predicted response of the rock socketed drilled shaft under the lateral load. Both, the orientation of the plane of transversely isotropy, and the degree of anisotropy (E/E’) has influences on the main two parameters required to characterize the p-y curve, the subgrade modulus (Ki) and the ultimate lateral resistance (pu).
In addition to the development of a hyperbolic p-y criterion of transversely isotropic rock, another p-y criterion for cohesive intermediate geomaterials (IGM) using hyperbolic mathematical formulation is developed herein by employing the results of a series of finite element (FE) simulations and the results of two full scale lateral load test for drilled shaft socketed into IGM.