Research on the Response Mechanism of Coal Rock Mass under Stress and Pressure

Abstract

In this paper, the strength and deformation failure characteristics of bearing coal rock mass are related to the confining pressure, and the SAS-2000 experimental system is used to carry out uniaxial and 3, 6, and 9 MPa triaxial tests on coal rock to assess the strength and deformation failure characteristics of coal rock under different confining pressure conditions. The results show that the stress–strain curve of coal rock undergoes four evolutionary stages after fracture: compaction, elasticity, plasticity, and rupture. With confining pressure, the peak strength of coal rock increases, and the elastic modulus increases nonlinearly. The coal sample changes more with confining pressure, and the elastic modulus is generally smaller than that of fine sandstone. The stage of evolution under confining pressure constitutes the failure process of coal rock, with the stress of different evolution stages causing various degrees of damage to coal rock. In the initial compaction stage, the unique pore structure of the coal sample makes the confining pressure effect more apparent; the confining pressure makes the bearing capacity of the coal rock plastic stage stronger, the residual strength of the coal sample has a linear relationship with the confining pressure, and the residual strength of the fine sandstone has a nonlinear relationship with the confining pressure. Changing the confining pressure state will cause the two kinds of coal rock samples to change from brittle failure to plastic failure. Different coal rocks under uniaxial compression experience more brittle failure, and the overall degree of crushing is higher. The coal sample in the triaxial state experiences predominantly ductile fracture. The whole is relatively complete after failure as a shear failure occurs. The fine sandstone specimen experiences brittle failure. The degree of failure is low, and the confining pressure’s effect on the coal sample is obvious.

Mechanical Behaviors and Precursory Characteristics of Coal-Burst in Deep Coal Mining for Safety-Sustainable Operations: Insights from Experimental Analysis

“…(2) Linear Figure 3 illustrates the mechanical curves of coal under multiaxial cyclic loading with various confining pressures, where the deviatoric represents the difference of axial stress and the confining presses (i.e., σ 1 − σ 3 ). It is evident that the deformation process of coal can be divided into four stages [21,22]: (1) Initial compaction stage: During this stage, the coal sample experiences cyclic loading, leading to the compaction of the original microcracks. The stress and strain exhibited during this stage are relatively low.…”

Experimental study on mechanical damage characteristics of water-bearing tar-rich coal under microwave radiation

“…Uniaxial, triaxial and cyclic loading and unloading tests were carried out indoors to simulate the underground environment of coal samples under different water content conditions. It is of great significance to explore the deterioration trend and failure characteristics of mechanical properties of coal samples under different water content conditions [27,28].…”

Burst Failure Characteristics and Energy Evolution Law of Coal with Prefabricated Cracks at Different Angles

“…Coal is a typical heterogeneous material that contains a large number of joints, cracks, or structural planes inside. Te instability and failure of coal mine roadways are caused by the initiation, expansion, and connection of internal cracks in the coal body [1][2][3][4]. With the gradual deepening of coal mining, the joint cracks of the roadway surrounding rock are more developed, loose, and broken, and the deformation of the roadway is aggravated [5][6][7][8][9].…”