Elastoplastic analysis of normal stiffness of bore wall of the rock-socketed pile based on Hoek-Brown failure criterion and cavity expansion theory

Abstract

The research on the shaft resistance governing by the sliding and shearing mechanism between the pile-rock interfaces is always a hot issue in the research of rock-socketed pile. All existing theoretical methods assumed that the normal stiffness of the bore wall of rock around the pile is constant which based on the elastic solution of cylindrical cavity expansion in a finite medium during the increasing of the relative displacement of the pile-rock interface. However, rock is not an ideal elastic material. In order to illustrate this problem, this paper combined the cavity expansion theory and the original Hoek-Brown failure criterion conducted an elastoplastic analysis of rock-socketed piles during the relative displacement of the pile-rock interface increases and derived the stress field and displacement field in the elastic and plastic phase. And, based on a case validation illustrated the difference between the elastic and elastoplastic solution of the normal stress increment with different radial displacement of the pile-rock interface and stated that only using the elastic solution of normal stiffness will overestimate the increment of normal stress at the pile-rock interface, and then overestimate the shaft resistance which will cause the design unsafety.