Uniaxial Creep Test Analysis on Creep Characteristics of Fully Weathered Sandy Shale

Abstract

The creep damage behavior of rocks is very important for evaluating the stability and safety of key rock engineering. Based on the Lianhua Tunnel Project in China, this paper aims to study the creep damage mechanics, the influencing factors and the creep constitutive models of sandy shale. In order to achieve these goals, a uniaxial compressive strength test and a creep test under different moisture contents and load levels were carried out. According to the test results, the creep parameters (elastic coefficients E1 and E2 and viscosity coefficients η1 and η2) of the Burgers Model were achieved, and the relationship between the creep parameters and moisture content, ω, was established accordingly (E1 = f(ω), E2 = f(ω), η1 = f(ω), η2 = f(ω)). A fully weathered sandy-shale creep constitutive model considering moisture content was finally obtained. Test results showed that creep deformation increases with any increase in load level or moisture content, and the influence of moisture content is more significant. For instance, creep deformation increased by 35% when the load increased by 50%, and creep deformation increased by 82% when the moisture content increased by 45%. In addition, the creep rate in the steady stage and the duration of the primary creep stage increased with any increase in moisture content or load level. The higher the moisture content, the greater the influence of creep deformation on the total deformation. The creep model of fully weathered sandy shale showed that the elastic coefficients (E1, E2) and the viscosity coefficients (η1, η2) are negatively correlated to moisture content; E1 is negatively correlated to load level; and E2, η1 and η2 are positively correlated to load level. Qualitative and quantitative analysis of fully weathered sandy shale can improve the existing research of creep properties and is expected to provide theoretical support for treatment of large deformation disasters in the fully weathered sandy-shale stratum.