Analysis of shear creep characteristics of carbonaceous mud shale in Huangshan limestone mining area under osmotic pressure

Aiming at the obvious creep effect of Permian soft interlayers under repeated rainfall in Southwest China, the shear creep test under osmotic pressure is carried out on the carbonaceous mud shale in the Huangshan limestone mining area in Sichuan Province, and the shear creep test curves are obtained, and by analyzing its creep characteristics and nonlinear breaking law, based on the traditional Nishihara model, a nonlinear creep model that can simultaneously describe the viscoelastic-plastic characteristics of carbonaceous mud shale is proposed, and the model is used to identify the shear creep parameters. Combined with FLAC^3D numerical simulation calculation, the deformation and failure characteristics of carbonaceous mud shale are studied, and the indoor test results and numerical simulation results are compared, and the numerical simulation results confirmed the reliability of the indoor test and the rationality of constitutive model and parameter selection. The results show that under the action of osmotic pressure, normal pressure and shear stress, the carbonaceous mud shale specimen undergoes a complete creep stage. The improved Nishihara model can fit the three stages of carbonaceous shale creep well, and the fitting effect on the accelerated creep stage is also very good. The numerical simulation results obtained by using FLAC^3D software to calculate the indoor shear creep test are consistent with the actual results.