The deformation characteristics of saturated mucky clay under subway vehicle loads in Guangzhou

Abstract

Since the long-term performance of subway tunnels is largely determined by the deformation of the soil around them, the study for the soil deformation characteristics under subway vehicle loads is important, especially in soft soil area. Based on a series of dynamic cyclic triaxial tests, the deformation characteristics of saturated mucky clay in Guangzhou were studied. The result shows that the failure cyclic stress amplitudes (CSA) and failure cyclic stress ratio occur when recoverable strain and accumulative plastic strain reaches approximately 0.22 and 15 %, respectively. Accordingly, the development of cyclic plastic strain is categorized into three types: steady state, rapid growth and instantaneous failure. When the stress level is below the failure CSA, the development of recoverable strain is nearly linear with accumulative plastic strain. To prevent and control engineering geological hazards induced by subway vehicle loads, vibration amplitudes of mucky clay around the subway tunnel axis must be closely monitored. More attention must be paid to soil deformation at the early operation stages of a subway line when mucky clay is sensitive to external loads. The strength of soil of the shallow ground should be considered as the basic parameters for study and design. The results of this paper can contribute to the design and maintenance of subway tunnels, as well as the prevention and control of tunnel axis deformation.