Research on damage characteristics and energy evolution law of coal rock under cyclic gradient loading

Abstract

In coal mining, the rock mass is often in the process of repeated cyclic loading due to the influence of excavation and unloading factors. In order to study the damage and failure characteristics and energy evolution law of coal and rock under cyclic gradient loading, a uniaxial cyclic gradient loading experiment was carried out on coal samples, and deformation failure characteristics, input energy density, dissipated energy density and damage variables of the coal samples under different cyclic gradient loading were compared and analyzed. The results show that with the increase of the cyclic gradient stress, the number of cycles and the peak strength of the coal samples decrease, which are 17.97, 14.86, 11.23, and 10.53 MPa; in cyclic gradient loading, most of the input energy density is stored inside the rock sample in the form of elastic strain energy, and the dissipation energy increases between 0.2% and 40% of the total input energy in a single cycle. Cumulative dissipation is selected as the quantitative index of the whole process of coal and rock damage, and the Logistic equation is used to fit the coal and rock damage, and the evolution model of coal and rock damage is obtained.

Keywords

• coal rock damage
• surrounding rock control
• cyclic gradient loading
• failure deformation
• dissipated energy
• energy evolution
• damage characteristics