Mechanicsanalysis Of Surrounding Rock Deformation Of Roadwayaffected By Deep Riding Mining And Its Stability Control

With the increasing depth of coal mining, the stability of roadway surrounding rock is deteriorating, and the requirements on support technology are increased, which has serious impact on the efficient and safe intensive production in coal mine. The surrounding rock stability of roadway affected by cross mining(RCM)has always been a difficult problem of safe production in coal mine. Especially for the roadway affected by deep riding mining(RADRM), which means that the roadway located at the bellow of the working face and the advancing direction of working face is along with the roadway axis,its surrounding rock is affected by the support pressure caused from the coal face mining for a long time and the deformation shows strong rheological properties, which gives rise to difficulties in stability control of surrounding rock. A synthetically study means combined with theoretical analysis, numerical simulation and field observations is applied to study systematically the mechanical mechanism of the stability of RADRM in deep and its control ways. And the study results with innovative significance are shown in the following:(1) The mechanics model of RADRM is established to analyze the rheological properties of surrounding rocks, and the visco-elastic-plastic theory is applied to study the stress distribution of roadway surrounding rock and its influence on the stability of surrounding rock and obtain the distribution law of the stress and deformation of roadway surrounding rock with the changing of the roadway depth H, the vertical distance h and the horizontal distance b between the roadway and the end of the working face above, and the estimated expression of the stress and the deformation of roadway with the time changing are respectively gained.(2) With the help of numerical simulation, the stability characteristics of RADRM in coal seam mining are analyzed and obtain the distribution law of the stress, the deformation and the plastic zone size of roadway surrounding rock with the changing of the roadway depth H, the vertical distance h and the horizontal distance b between the roadway and the head of the working face above. The study results indicate that when the horizontal distance b between the roadway and the head of the working face above is smaller, the roadway stability is affected by the advanced abutment pressure in working face and the lateral abutment pressure. Especially the roadway roof and the roadway side near to the end of working face are affected seriously by the coal seam mining above, and their rheological effect deduced from the high stress effect for a long time is the important reason for the hidden trouble of the roadway stability.(3) The rheological properties of the surrounding rock of RADRM is analyzed to investigate the time dependent properties of the stress, the deformation and the plastic failure zone of roadway surrounding rock, and obtained the influence of the roadway depth H, the vertical distance h and the horizontal distance b between the roadway and the end of the working face above on the rheological and failure properties of the roadway surrounding rock. The study results indicate that the stress of surrounding rock tended to decrease with time passing, and the stress concentration zone gradually expanded to the deep surrounding rock; the deformation and the plastic failure zone of surrounding rock are increase sharply with time passing, showed rapid initial increase and the surrounding rock deformation tends to stability after 60 days. The rheology of surrounding rock is mainly resulted from its viscoplastic creep.(4) Aimed at the stability of RADRM in a coal mine, the corresponding field observation scheme is designed. We have conducted long-term monitoring on the surface displacement of roadway, the deformation of surrounding rock inside, the anchorage situation of bolt(cable), and obtained the deformation failure law and rheological properties of the roadway during the coal seam mining and for a long time after mining.(5) Grouting can improve the basic mechanical properties and Anti-rheological properties of surrounding rock. Taking advantage of this characteristic and combined the bolt(cable) support technology, the combined bolt-grouting support scheme is presented to control the stability of RADRM, and designed the special grouting anchor adapted to the testing roadway conditions. Field observation were carried out to validate that this support technology can control effectively the rheology deformation of RADRM and insure the stability and safe of the roadway surrounding rock during the coal seam mining above.The study results can provide important reference to stability control of the roadway surrounding rock on the similar condition.