Bearing behavior of rock socketed pile in limestone stratum embedded with a karst cavity beneath pile tip

Abstract

This paper investigates the bearing behavior of axially loaded rock socketed piles in limestone stratum embedded with a karst cavity beneath the pile. The pile foundation supporting a cross-river bridge located in a karst area in China is considered. Based on this project, three-dimensional finite element analyses are performed to capture the effects of pile length, pile diameter, limestone cohesion, and cavity roof thickness. Their impact on the bearing characteristics of the pile is comprehensively outlined through analysis of load-settlement curves, variations in pile bearing capacity, distributions of axial pile force and pile side friction, as well as contours of vertical ground and cavity roof displacement. It is found that the load-settlement curves exhibit the saltation type, based on which the pile-bearing capacity can be conveniently obtained. The pile bearing capacity increases nonlinearly with increasing the pile length, whereas almost linearly with an increase in the pile diameter, limestone cohesion, and cavity roof thickness. For the considered conditions, larger magnitudes of vertical ground displacements occur primarily surrounding the pile side in the pebble layer and at the pile bottom. This is attributed to the weakening effect of the karst cavity on the bearing capacity of the cavity roof. The achievements from this study are beneficial for the design optimization of rock socketed piles in karst areas.