Instability Mechanism And Control Of Three-dimensional Stress Difference In Surrounding Rock Of High Stress Trapezoidal Coal Roadway

Surrounding rock of high-stress trapezoid coal roadway is seriously disproportionately broken as well as the roadway is difficult to repair and the maintenance cost is high.Therefore,the technology for the control of unbalanced damage and deformation surrounding rock still needs to be improved.Based on the engineering background of 151104 mining face of Anhui coal mine,this paper uses laboratory tests,theoretical analysis,numerical simulation,and field tests to study the mechanism of three-dimensional stress difference instability of surrounding rock in high-stress trapezoid coal roadway.The high-stress trapezoid coal roadway surrounding rock control technology based on the three-way stress difference is proposed.The research results can provide a scientific basis for the selection of high-stress trapezoid coal roadway support schemes.The main research contents and results are as follows:(1)Based on the results of engineering investigations and laboratory tests,combined with the complex variable function theory and numerical simulation methods,the failure and deformation characteristics of coal and rock bodies with different three-dimensional stress differences are analyzed,and the surrounding rock of high-stress trapezoid coal roadway is revealed from the perspective of the three-dimensional stress differences Instability mechanism.The analysis results show that the key to the surrounding rock instability of high-stress trapezoid coal roadway is the three-dimensional stress difference of coal and rock bodies.The essence of the process of roadway surrounding rock deformation and instability is that the high threedimensional stress difference unit drives the low three-dimensional stress difference unit process of destruction.That is,after the three-dimensional stress difference of the coal rock body exceeds its withstand limit value,the surrounding rock will be damaged and deformed,and the greater the three-dimensional stress difference,the greater the degree of fracture and deformation of the surrounding rock;the greater the change rate of the three-dimensional stress difference of the coal rock,The larger the deformation range of surrounding rock failure.With the change of the three-dimensional stress difference of the surrounding rock,the surrounding rock of the tunnel enters the fracture zone,plastic zone and elastic zone from the surface to the inside in the radial direction.Among them,the change states of the three-dimensional stress difference of the surrounding rock fracture zone,plastic zone and elastic zone with time increase are: first increase and then decrease to stability,first increase and then stabilize,and continue to increase;In the process of entering the rupture zone,plastic zone and elastic zone in order from the surface to the inside in the radial direction,the change curve of the three-dimensional stress difference increases first and then decreases to the original rock stress state.(2)According to the research results of the instability mechanism of the three-dimensional stress difference of the surrounding rock of the high-stress trapezoid coal roadway,the control technology of the surrounding rock of the trapezoid coal roadway based on the threedimensional stress difference is clarified,and the reduction of the three-dimensional stress difference and the improvement of the three-dimensional stress of the surrounding rock are proposed.The support method of bolt-cable with different bearing capacity was analyzed and verified by numerical simulation method.The analysis results show that the method of bolt-cable support to reduce the three-dimensional stress difference and improve the bearing capacity of the surrounding rock three-dimensional stress difference can effectively control the stability of the surrounding rock.That is,after applying different bolt-cable to the left,right and top plates to provide different supporting forces,the displacement of the surrounding rock roof and bottom plates and the two sides is greatly reduced.Therefore,the bearing capacity of the threedimensional stress difference of the surrounding rock side is improved.The difference in threedimensional stress is reduced by 0.67 MPa,and the problem of non-equilibrium failure deformation of surrounding rocks is effectively controlled.(3)The best plan of surrounding rock control effect is applied to the site.The on-site monitoring results show that the maximum displacements of the top and bottom walls of the surrounding rock and the two gangs are 111.5 mm and 64.6 mm,respectively.The monitoring results show that the supporting scheme can effectively control the stability of the surrounding rock.At the same time,according to the monitoring results of the stress changes of the bolt-cable,the bolt-cable provides a certain supporting force,which not only reduces the three-dimensional stress difference of the surrounding rock,but also improves the bearing capacity of the threedimensional stress difference of the surrounding rock.It is further verified that the surrounding rock control technology based on the three-dimensional stress difference can effectively control the stability of surrounding rock.