Investigating Strength and Deformation Characteristics of Heavy-Haul Railway Embankment Materials Using Large-Scale Undrained Cyclic Triaxial Tests

Abstract

Heavy-haul railway embankments in China are generally constructed with coarse-grained granular (CGS) materials. The accumulation of permanent deformations in CGS materials remains a significant concern and technical challenge because the CGS layer sustains a considerable portion of the intense train-loading transferred from overlying structures. Previous research studies demonstrated that the critical cyclic stress (CCS) level significantly affects the accumulative permanent (or plastic) deformation. This paper presents the results from a series of repeated-load, undrained, permanent deformation triaxial tests conducted in the laboratory using a customized large-scale triaxial apparatus. CGS specimens prepared with different moisture contents were subjected to different combinations of confining and deviator stress levels. The accumulation of permanent axial strain as a function of the number of load cycles was recorded for each specimen during the tests. The influences of moisture content, confining pressure, and deviator stress on modulus and permanent axial strain accumulation characteristics were analyzed. Empirical formulas for calculating the elastic modulus and accumulated permanent axial strain are proposed. The findings in this study could provide guidance for designing similar heavy-haul railway embankments.