Study On Fault Activation Under Mining Action And Its Influence On Coal And Rock Mass Stability

Fault is the most common geological structure in underground coal mine,and is an important geological factor affecting coal mining.Because the existence of faults disturbs the state of continuous and integral occurrence of rock stratum,the stress distribution nearby is abnormal,and the mining effect is very prominent,which has great influence on the arrangement of working surface,mining design and support technology,etc.It is very easy to induce dynamic disasters such as rock burst,which poses a serious danger to the safety production of coal mines.On the basis of the theory and method of rock mechanics,this paper analyzes the mechanism of mechanical action of fault activation induced by mining action,and studies the process of working surface heading towards fault by laboratory test and numerical test,the main achievements are as follows:(1)The maximum static frictional force on the fault plane shows a decreasing trend by the increase of coal body strain and the passage of time,which provides a prerequisite for the loss of mechanical balance on the fault plane.(2)The discrete-continuous coupling method is used to study the mining process of the upper and lower working faces of the normal fault.When the upper and lower working faces of the normal fault advance toward the fault,the surrounding rock of the working face is sheared and the plastic zone of the upper shows a "saddle shape".The plastic zone of the lower shows a "butterfly";when mining upper on the normal fault and the working face is 20 m,30m and 40 m away from the fault respectively,the possibility of activation and destabilization is highest in the upper fault,middle fault and lower fault,the peak value of fault slip is 7.98cm;when mining under normal faults and the working face is 40 m,30m and 10 m away from the fault respectively,the possibility of activation and destabilization is highest in the upper fault,middle fault and lower fault,and the peak value of fault slip is 23.39 cm.(3)The discrete-continuous coupling method is used to study the mining process of the upper and lower working faces of the reverse fault.When the upper and lower working faces of the reverse fault advance toward the fault,the surrounding rock of the working face is sheared and the plastic zone shows a "butterfly";when mining upper on the reverse fault and the working face is 40 m,30m and 50 m away from the fault respectively,the possibility of activation and destabilization is highest in the upper fault,middle fault and lower fault,the peak value of fault slip is 13.28cm;when mining under reverse faults and the working face is 60 m,30m and 20 m away from the fault respectively,the possibility of activation and destabilization is highest in the upper fault,middle fault and lower fault,and the peak value of fault slip is 43.40 cm.(4)When the working face mining in the hanging wall of the normal and reverse faults,crack develop from the lower of the fault to the middle and upper of the fault;When the working face mining in the footwall of the normal and reverse faults,the crack develop from the upper of the fault to the middle and lower of the fault.In the process of working face advance towards the fault,reverse faults are more susceptible to mining face disturbances than normal faults,and the hanging wall mining disturbance is more affected than the footwall.Based on mechanical analysis and FLAC3 D / PFC3 D numerical program,the activation law of fault under the influence of mining face and the stability of coal and rock mass in fault area are analyzed in this paper.According to the obtained rule,the methods of bolt and grouting control in coal and rock mass,in outside,roof support are put forward to improve the self-bearing capacity of surrounding rock and the interaction and adaptability between support structure and surrounding rock.On the basis of improving the self-strength of coal and rock mass,the external restraint of resisting deformation of coal and rock mass is strengthened,the response behavior of internal and external causes of coal and rock mass is reduced,and the safe mining of coal mine is realized.