Early Warning Mechanism And Control For Roof Separation Of Underground Openings In Soft Argillaceous Rock Under High Stress

The deformation characteristics of surrounding rock in Soft Argillaceous Rock Roadway under High Stress during roadway excavation are fracture development,large deformation and poor self-stability.After the support is completed,it still maintains long-term rheology,which leads to difficulties in roadway maintenance and roof separation and roof fall accidents.At present,the incidence of roof accidents in coal mines in China is the highest,and the number of casualties is also the largest.Therefore,the mechanism of roof separation and its early warning mechanism are the key issues for the construction safety and the long-term stability of surrounding rock in soft argillaceous rock roadway under high stress.In this thesis,the intersection of main drainage pump opening and main substation and the central return airway in Libi Mine are taken as the research objects.The field measurement,laboratory test,theoretical analysis,numerical simulation and industrial test are used to reveal the evolution law and separation mechanism of roof cracks in soft argillaceous rock roadway under high stress.The early warning mechanism of roof separation in soft argillaceous rock roadway under high stress is established,and the roof separation control scheme in soft argillaceous rock roadway under high stress is put forward.The following main research results are obtained:（1）The main influencing factors of roof separation in soft argillaceous rock roadway under high stress of Libi Mine were determined.According to the mechanical properties test of soft argillaceous rock and the XRD diffraction experiment results of surrounding rock phase,combined with the in-situ stress test results and the borehole detection results of surrounding rock structure.It is concluded that the roof of the main drainage pump opening is under the coupling of multiple factors,that is,under the influence of low-strength argillaceous soft rock,high ground stress,roadway group excavation disturbance and large section roadway factors,a large number of cracks are developed in the shallow roof,resulting in roof separation and slurry cracking.（2）The roof fracture evolution law and separation mechanism in soft argillaceous rock roadway under high stress are revealed.The mechanical model of roof separation is established to reveal the mechanical mechanism of roof separation in soft argillaceous rock roadway under high stress.According to the engineering geological conditions of soft argillaceous rock roadway under high stress in Libi Mine,FLAC^3D and UDEC numerical simulation software were used to simulate and analyze the influence of roadway group excavation disturbance and different buried depth,tectonic stress and roof bottom lithology combination conditions on the roof crack evolution law and separation in soft argillaceous rock roadway under high stress.It is concluded that under the action of horizontal tectonic stress field,the shallow argillaceous soft rock of the roof is subjected to tensile-shear composite failure to produce discontinuous structural planes,and the discontinuous structural planes are connected to form a fracture network,which eventually leads to the separation of the roof.（3）The separation warning mechanism in soft argillaceous rock roadway under high stress is established.With the help of analytic hierarchy process,the safety evaluation index of roof separation in soft argillaceous rock roadway under high stress is determined,and the risk assessment method and control management measures of roof separation in soft argillaceous rock roadway under high stress are put forward.The on-line monitoring and early warning system of roof separation is established,and the separation risk of roof plate of main drainage pump opening in Libi Mine is comprehensively evaluated.The results show that the roof plate of main drainage pump opening belongs to high separation risk.（4）The control scheme of roof separation in soft argillaceous rock roadway under high stress is put forward.According to the comprehensive evaluation results of roof separation risk,a combined reinforcement scheme of prestressed anchor cable+shotcrete+shallow hole grouting is proposed for the roof separation problem of main drainage pump opening in Libi Mine.The feasibility of the combined reinforcement scheme was verified by numerical simulation and industrial test.The field application effect is good,and the roof separation of the roadway is effectively suppressed.Aiming at the special section of the central return airway,a new combined support scheme of prestressed full-length anchorage technology and prestressed anchor cable+shotcrete is proposed.There are 85 figures,15 tables and 101 references in this thesis.