Study On The Creep Instability Mechanism And Control Technology Of Soft Coal Roadway In Quandian Coal Mine

Owing to the low strength and remarkable rheological properties of surrounding rock,soft coal roadway has always been a difficult problem in mine construction.The coal quality of No.21 coal seam mined in Quandian Coal Mine is soft,the fragmentation is small,and it is loose and grainy.under the existing shed cable support,there is a large convergence of the two sides of the roadway,and the floor heave and top subsidence seriously lead to the difficulty of support.Taking the tailgate of 11000 working face in Quandian Coal Mine as the research object,this thesis studies the creep mechanical properties of soft coal and the creep instability mechanism of soft coal roadway by using the methods of field investigation,laboratory test,theoretical analysis and numerical simulation.A strong active support technology is put forward,and the main research results are as follows:(1)Through on-site investigation and on-site drilling snooping test,the deformation and internal structure characteristics of headgate in 11050 working face of Quandian Coal Mine are analyzed.The roadway deformation under the original shed and cable support has obvious characteristics of accelerated creep,the internal structure of the surrounding rock is obviously destroyed,the sandy mudstone in the roof and coal pillar is seriously broken,the cracks are developed obviously,and the coal bodies of the two sides are relatively intact without obvious cracks.(2)The uniaxial compression creep test was carried out,and the strain-time curve of soft coal specimen under uniaxial creep was obtained.Based on the idea of discrete element,the concept of unbonded contact is introduced into the Coulombslip joint model,and a new nonlinear discrete creep model of soft coal is established.Based on this model,the creep characteristic curve and creep crack growth law of soft coal under different confining pressure were studied by UDEC7.0 simulation.The results show that increasing confining pressure can increase the initial strength of accelerated creep of coal,which is helpful to reduce the amount of creep deformation of coal or avoid the occurrence of unsteady creep.(3)Taking the tailgate of 11000 working face as the research background,the creep instability characteristics of soft coal roadway without support and shed cable support are simulated and studied.the creep instability mechanism of soft coal roadway in Quandian Coal Mine is revealed: the creep deformation of coal particles in the surrounding rock of soft coal roadway and the development of meso-cracks between particles cause the creep deformation of the roadway as a whole.(4)A strong active support technology based on the principles of "high pretension Anchorage","high stiffness surface protection" and "structure compensation" is put forward.The simulation verifies that the surrounding rock deformation of soft coal roadway is effectively controlled under strong active support.The distribution range and density of cracks are obviously reduced,and the optimization of support parameters is simulated.(5)The support technology is applied to the tailgate of 11000 working face to dynamically monitor the deformation of surrounding rock and the force of anchor cable.During the service period of the roadway,the deformation is small,the supporting body plays a good role,and there is no fracture failure phenomenon.It shows that the proposed one-time strong active support technology can effectively control the creep instability of soft coal roadway.