Development of lateral capacity-based envelopes of twin-pile group under combined V–H–M loading

Abstract

This study explores the bearing capacity of a three-dimensional (3D) twin-pile group subjected to combined vertical (V), horizontal (H), and bending moment (M) load using finite element limit analysis coupled with lower and upper bounds and mixed Gauss element formulations. The numerical results based on different element formulations are compared with those of the previous study under single-component loading. The failure envelope in the 3D V– H–M loading space is constructed through a simplified loading strategy. Several typical collapse mechanisms are identified to be associated with different load component values. Moreover, the influence of the pile spacing-to-diameter ratio, pile length-to-diameter ratio, and loading direction angle on the combined bearing capacity is discussed herein. A set of charts is developed as well. Finally, a closed-form design expression of failure envelopes considering the abovementioned influential parameters and the combined V–H–M load are derived based on the obtained numerical results.