Efficient solution for a single pile under torsion

Abstract

This paper presents a simple and more efficient solution mechanism for solving the linear response of a single pile with a circular cross section under torque in “n” multilayered soils. The pile-soil system is modeled by a series of independent springs distributed along the pile shaft with each spring representing an individual layer of soil. The properties of each soil layer are assumed constant with the allowance for variation from layer to layer. The method is based on the energy principles and variational approach initially proposed by Vallabhan and Mustafa (1996) for a single pile under a vertical load, developed by Guo and Lee (2001) for a single pile under a lateral load, and developed by Zhang (2010) and Misra et al. (2013) for a pile under torque. With the proposed iterative solution scheme, the equivalent stiffness of a soil-pile system of individual pile segments is calculated from the bottom element to the top element, while torque and the angles of twist are calculated from the top element to the bottom element of the pile without having to simultaneously solve a large number of equations. The solution provides: (1) the distribution of the angles of twist, (2) the distribution of torque along the pile and (3) the equivalent stiffness of the pile-soil system. A comparison of the results of the analysis using the proposed new solution mechanism with those of existing analytical solutions and a three-dimensional finite element analysis shows that the proposed method is much more efficient.