The analysis of asbestos-cement shell pile performance under off-center loading and forced torsion

Abstract

The paper discusses the new design of a round pile with a relatively smoother surface, developed in an attempt to eliminate excessive negative friction forces. A theoretical study has been conducted into the performance of asbestos-cement shell pile exposed to off-center loading, which occurs in response to uneven deformations in the surrounding soil and seismic loads. The cross section of the upper eccentrically compressed part of a flexible asbestos-cement-pipe-concrete pile element is considered. When considering the stress-strain state of flexible eccentrically compressed asbestos-cement-pipe-concrete piles, the premise of compliance with the hypothesis of flat sections is accepted. With the predicted intensive development of loading friction forces, a method is proposed for preliminary turning these round piles around the axis to remove the main part of the adhesion between the side surface of the pile with the base soil. Theoretically, the stress-strain state of the indicated pile, which is formed during its torsion around the axis, was estimated. The pile is considered as a composite element consisting of a concrete cylinder and an asbestos-cement pipe. As a first approximation, we assume that there are no body forces, and the concrete core and the asbestos-cement shell are rigidly linked. According to the Saint-Venant principle, it can be considered that for a twisted rod at a sufficiently large distance from its ends, the stresses depend on the torque and do not depend on the method of distribution of the forces that give this moment over the end sections. Based on the basic equations of the theory of elasticity, it follows that in a pile of circular cross section, bounded by a concentrically round shell, the cross sections remain flat during torsion.