Deformation Failure Mechanism And Control Technology Of Right Angle Trapezoidal Roadway In Inclined Coal Seam

Inclined coal seam coal reserves account for 35%of the total coal resources in China,and its development and utilization plays an important role in energy strategy.However,due to the complex surrounding rock stress environment and significant asymmetric deformation and failure characteristics of inclined coal seam roadway,which leads to the difficulty of roadway support.It has seriously restricted the safe and efficient mining of coal resources in inclined coal seams.Due to the influence of roadway section shape and coal seam inclination effect,which leads to the difficulty of mechanical analysis of roadway’s surrounding rock stressdeformation in inclined coal seam and the unclear transmission law of the magnitude and direction of principal stress.At present,there is a lack of systematic research on the stress distribution and deformation failure mechanism of roadway surrounding rock in inclined coal seam,and the research on the control technology of roadway’s surrounding rock still needs to be improved.Therefore,taking the inclined coal seam roadway in Shitanjing No.2 mining area as the engineering background,using the research methods of theoretical analysis,numerical simulation,similar physical simulation test and field engineering test,this paper studies the asymmetric stress and deformation failure distribution law of roadway’s surrounding rock in inclined coal seam,the evolution characteristics of principal stress transfer path,and the instability mechanism of self stable equilibrium circle considering principal stress deflection.The control technology of surrounding rock deformation of right angle trapezoidal roadway in inclined coal seam is put forward.The main work and research results are as follows:(1)The mechanical model of roadway’s surrounding rock in inclined coal seam is constructed by using complex variable function and elastic mechanics theory,the mapping function solving method is improved,and the inclination coefficient is introduced,which deduces the analytical solution of stress and deformation of roadway’s surrounding rock suitable for arbitrary inclination and section shape.The asymmetric stress distribution law and progressive deformation failure mechanism of the roadway surrounding rock of inclined coal seam are revealed,that is,the sharp corner on the roofs left side is first destroyed-the shallow surrounding rock of the two sides is destroyed-the effective span of the roof is increased-the two sides are destroyed and extended to the deep-into the vicious cycle of destruction.Based on the analytical solution of displacement and computational geometry,the calculation model of asymmetric deformation degree of inclined coal seam roadway is established,and the quantitative and visual representation of roadway’s asymmetric deformation degree with timing and regionality is realized.(2)The stress,deformation and plastic zone of surrounding rock of inclined coal seam roadway with different inclination and different section shapes under different loads are analyzed by numerical simulation method.The progressive asymmetric failure law of roadway surrounding rock is revealed quantitatively and intuitively,that is,the peak stress and stress concentration area of roadway surrounding rock in inclined coal seam show an asymmetric distribution trend that the right side is greater than the left side.With the increase of dip angle,the asymmetric distribution characteristics of roadway surrounding rock are more obvious,and the asymmetric stress concentration and deformation failure of right angle trapezoidal roadway surrounding rock are the most serious.With the increase of load,the greater the stress concentration and deformation,and the stress concentration area transfers from shallow to deep.(3)The similar physical model tests of inclined coal seam roadway with different dip angles and different section shapes are carried out,the DIC measurement technology is improved,the real-time monitoring of roadway surrounding rock stress field and principal strain deflection trajectory is realized,and the deformation and failure law of inclined coal seam roadway under the condition of asymmetric stress distribution and stress direction deflection combination is revealed.It is found that the asymmetric arch principal strain transmission envelope is formed in the roof rock of right angle trapezoidal roadway,and its self stable equilibrium circle presents a semi oval deflection to the left side.With the increase of dip angle,the asymmetric deformation and failure of roadway surrounding rock is more obvious,and the deformation and damage of right angle trapezoidal roadway is the most serious.The crack along the inclined direction of the coal seam first appears at the roof corner of the left side,which is the key to the stability control of the roadway.(4)The transmission path of the principal stress component and direction of the roadway surrounding rock in inclined coal seam is analyzed by using the theory of elasticity and numerical simulation method,and the asymmetric evolution characteristics of the principal stress deflection and its driving effect on the deformation and failure of the roadway are revealed,which is verified by the similar physical simulation test.The phenomenon of principal stress deflection affects the bearing capacity and failure mode of roadway,and the stability Fs of roadway surrounding rock under the action of principal stress deflection is defined.When Fs>0,the two sides of roadway are stable.The crack development control method at the sharp corner of the left side is put forward,and the sensitive area of the main stress direction of the surrounding rock is divided.The method of arranging bolts at the sharp corner of the left side is proposed to change the stress deflection track,drive the main stress direction away from the sensitive area of the direction,and improve the stability of the roadway’s surrounding rock.(5)The mechanical model of self stable balance circle of right angle trapezoidal roadway in inclined coal seam considering the deflection of principal stress direction is established,the boundary stress state is analyzed,and the stability control mechanism of self stable balance circle is clarified.Combined with the asymmetric stress distribution,principal stress deflection effect and progressive deformation and failure characteristics of roadway’s surrounding rock,the asymmetric support principle is put forward:asymmetric combined support of bolt(cable)and metal mesh to increase the stability of roadway surrounding rock;Strengthen the support of weak parts of roadway and reduce the stress state grade of self stable balance circle;Differential support is carried out according to the deflection angle of principal stress to improve asymmetric deformation and failure;Optimize the installation angle of anchor bolt(cable)and control the deflection track of principal stress.The asymmetric support scheme of"the anchor bolt(cable)is inclined to the right side,and area of sharp corner is densified and extended support" is designed,and verified by numerical simulation and field engineering test.