关键词:

采动应力 , 蠕变速率 , 疲劳损伤 , 硬化作用 , 瓦斯抽采

Abstract: In the process of coal mining, the coal body in the mining space is always under the combined disturbance of mining dynamic load and high static load, and it is difficult to determine the pressure relief position of the overburden under the combination of dynamic and static loads due to the fact that the cumulative characteristics of superimposed damage caused by cyclic load and creep are not clear. To this end, the MTS815 testing machine was used to carry out different axial creep compression tests after cyclic addition and unloading under the condition of confining pressure of 10MPa. The results show that the elastic modulus of unloading is higher than that of the loading process in the cyclic loading cycle. The Poisson's ratio showed a similar trend, and the gap between the elastic modulus and the Poisson's ratio became smaller during loading and unloading. The stress-strain response exhibits hardening and softening effects under constant deviator stress, and the triaxial?compressive?strength (TCS) has a dominant hardening effect under low deviator stress. On the other hand, the softening effect is more obvious under the action of higher deviator stress. The evolutionary characteristics between axial strain rate and volume strain rate can be well described by the negative exponential function relationship. The coal and rock mass at the boundary of mining pressure relief has experienced periodic failure and continuously increasing creep stress. Therefore, based on the creep evolution law of coal and rock mass, the appropriate time is selected to determine the boundary, which provides a quantitative basis for the prevention and control of disasters dominated by stress evolution. This study can provide a certain reference for preventing coal and rock dynamic disasters and determining the spatial location of pressure relief gas extraction.Key words: Mining-induced stress; creep rate; fatigue damage; hardening effect; gas drainage