Study On The Deformation Mechanism And Control Of Surrounding Rock With Roof Cutting And Pressure Releasing In High Stress Roadway Driving Along Next Goaf

In recent years,the depth and intensity of coal resources mining have been increasing,and roadway driving along next goaf is facing many challenges,such as high stress,strong mining and complex geological environment,resulting in severe mining pressure,impact disaster and serious deformation of surrounding rock,which restricts the safe and efficient mining of coal resources.However,at present,the failure mechanism of surrounding rock and corresponding theory and control technology could not effectively resolve the instability of deep roadway driving along next goaf.It has become an urgent task to carry out in-depth targeted research.The study on the deformation mechanism and control of surrounding rock with roof cutting and pressure releasing in high stress roadway driving along next goaf,as an important guarantee to deal with this problem and realize the sustainable and rapid development of coal resources,has a wide range of theoretical value and practical significance.In this dissertation,from the perspective of roof structure movement and surrounding rock stability control,failure process of rock mass structure,migration characteristics of overlying strata,roof presplitting de-stressing mechanism of surrounding rock,optimum design of coal pillar width,stress distribution and deformation effect of roadway were studied systematically by laboratory test,theoretical analysis,numerical simulation,physical model test and field industrial practices.The stability control system of surrounding rock in high stress roadway driving along next goaf,on the core of roof presplitting de-stressing,collapsed rock mass filling and coal pillar width design,was proposed.The innovation and achievements could be summarized as follows:(1)The mechanical parameters of coal and rock mass were obtained,revealing the failure evolution process of surrounding rock.In the shallow region of roadway roof,the rock mass was seriously damaged,mostly in the form of transverse fracture and rock dislocation;the failure mode of deep rock mass was mainly in the form of longitudinal fracture and roof separation.With low strength of coal seam and many fissures,the damage scope of coal pillar was wide.Meanwhile,the fissures expanded and connected laterally,finally developing into fracture zone.The fracture,rotation and subsidence of main roof above roadway directly affected stress distribution of two ribs in roadway,resulting in different failure range and asymmetric deformation characteristics of the coal pillar and the solid coal rib in gob-side entry roadway.(2)The mechanical model of the higher roof rock beam under the condition of broken gangue supporting in goaf was established,obtaining the bending deformation characteristics of the higher roof rock.The mechanical model of immediate roof deformation and coal pillar bearing in roadway was established,revealing the displacement evolution law of roof under the coupling influence of rock rotation angle,gangue resistance,elastic modulus and thickness of immediate roof,roadway width and roof support strength.The effect of plastic zone width on the stability of coal pillar was clarified,putting forward the design basis of coal pillar width for gob-side entry roadway.(3)The de-stressing mechanism of roof presplitting on surrounding rock structure was revealed,proposing the design methods to optimize key presplitting parameters,such as roof cutting angle and roof cutting height.Through the analysis of key presplitting parameters,when the roof cutting angle reached the optimal value,sliding speed of the roof in goaf along the presplitting cutting line was accelerated,and length of the lateral suspended roof structure decreased,reducing the overlying strata load borne by coal pillar and solid coal rib.When the roof cutting height reached the optimal value,the caving rock mass could fill the goaf better and form a stable bearing structure for supporting the upper strata,effectively relieving the impact disturbance of the higher roof rock falling on roadway and actively achieving the pressure relief of roof strata.(4)The evolution characteristics of stress and energy distribution for lateral coal and rock mass under the condition of roof presplitting and filling in goaf were studied.The deformation evolution law and load transferring mechanism of surrounding rock with different coal pillar widths were analyzed.The peak value of vertical stress and strain energy density in lateral coal seam was transferred to the deep region of rock mass,and a decreasing stress zone was formed at the edge of the coal wall after presplitting and roof cutting,effectively releasing the elastic strain energy stored in the shallow region of coal seam and providing a favorable stress environment for roadway driving along next goaf.(5)The movement characteristics and structural fracture patterns of roof strata with the condition of collapsed rock mass filling were studied by the physical model test,revealing the relationship between bed separation and fracture development and mining disturbance.The loading mechanism of roof strata movement on the surrounding rock was explained,grasping the distribution characteristics of stress and the evolution law of displacement and apparent resistivity for gob-side entry roadway roof under the influence of presplitting and roof cutting.(6)Based on the relevant design principles determined by theoretical analysis,physical model test and numerical simulation results,the deformation control system of surrounding rock for roadway driving along next goaf,on the core of roof presplitting de-stressing,collapsed rock mass filling and coal pillar width design,was constructed.The technical scheme was applied to the field industrial practices,obtaining the successful control effect of deformation,reducing the width of coal pillar in roadway driving along next goaf and further verifying the adaptability and feasibility of the research results in this dissertation.There are 97 figures,17 tables and 247 references.