Research on nonlinear damage hardening creep model of soft surrounding rock under the stress of deep coal resources mining

Abstract

To better understand the creep mechanical behavior of deep soft rock coal seam and more accurately predict the long-term deformation of the surrounding rock. Firstly, the electron microscope scanning test under different magnifications and a step loading creep test of deep soft rock were carried. the creep of the soft rock has the characteristics of ”sudden change”, and the propagation and combination of crystal particle cracks lead to the damage of rock mass, and the extrusion and dislocation movement of grains along the cavity hardens the rock mass. Deep rocks have both damage and hardening mechanisms in the creep deformation process, and there is a game relationship between them. Secondly, the damage variable and hardening function are introduced into Hooke’s body and Kelvin’s body, respectively, and connected in series with the adhesive dashpot with nonlinear viscosity coefficient containing power function, to establish the nonlinear damage and hardening creep model of three elements. Finally, the creep model agrees with the creep test data, which can accurately determine the opening time point of accelerated failure and the long-term strength of deep soft rock. This study provides a theoretical basis for creep laws of soft rock, which can effectively guarantee the long-term stability of deep energy extraction projects.