Study On Creep Characteristics Of Coal Rock With Pressure Hole

With the rapid development of our economy,the demand for energy also increases,and coal as one of the main sources of energy,its mining depth increases,after entering deep mining,the mine is also in a state of high stress,drilling pressure relief is an important means to alleviate high stress zone.However,with the passage of time,the creep around the borehole seriously threatens the stability of coal rock mass and the safety of coal mining.The creep failure of rock is very complicated,and it is one of the important factors to induce serious disasters in deep mining.It affects the long-term stability of rock mass in many engineering practices and theoretical studies.Therefore,in order to study the creep characteristics of coal rock with pressure relief holes,this paper takes Jixian 9~#coal mine in Shuangyashan City as the research object,and carries out the creep tests of intact coal rock and coal rock with different diameter pressure relief holes under different stress levels under uniaxial compression.FLAC3D is used to establish a numerical test model for creep test simulation.Taking Jixian 9~#coal mine in Shuangyashan City as the engineering background,the stability and spatio-temporal evolution of roadway surrounding rock are studied,The results show that:(1)Using YR-2000 rock creep instrument,creep tests of coal and rock mass under different pressure relief pore sizes were carried out,and the influence rule of different pore sizes on coal and rock mass damage was analyzed.It was verified that the existence of pressure relief pore reduced the cohesion of particles in the sample and the elastic modulus of the sample,resulting in the sample deformation more easily.Therefore,the size of pressure relief hole has a certain influence on the axial strain of coal rock.The instantaneous strain and creep of coal rock are affected by the size of pressure relief hole,and gradually increase with the increase of the size of pressure relief hole at the same stress level.(2)Based on the analysis of the laboratory test results,the Burgers model parameters of each test were obtained.The numerical simulation results using FLAC3D software are very similar to the actual test results,indicating that the Burgers model can better reflect the physical and mechanical properties of coal rock creep.(3)Pressure relief holes have a significant impact on the deformation of coal and rock,providing a certain deformation compensation space for coal seam,so that under the same stress level,the creep variable of the sample with pressure relief holes is larger than that of the intact sample.At the same stress level,the instantaneous strain and creep of coal rock gradually increase with the increase of the size of pressure relief hole.(4)There is a limit stress value of coal rock mass,beyond the limit stress of coal rock mass,will evolve new disasters;Therefore,reasonable arrangement of pressure relief holes within this range can play a role in pressure relief,reduce the possibility of rock burst,provide certain free space for coal rock deformation,and provide corresponding control effect on roadway surrounding rock deformation.The conclusion has a good theoretical significance for the long-term strength analysis of coal rock mass with pressure relief holes and rock burst relief.