| In China,there is a lot of serious unbalance between mining and excavation in coal production,which is caused by the difficulty in tunneling and low efficiency in rock excavation.In order to alleviate this problem and improve the driving efficiency of hard rock roadway,this thesis carried out an experimental study on the drilling and driving technology of rock roadway burst and hole layout,and studied the failure mechanism of rock burst,the influence law of the parameters of rock burst and hole layout by means of simulation combined with experiment,so as to provide references and solutions for the application of drilling and hydraulic fracturing breaking rock technology in coal mine rock roadway.The process of crack expansion is divided into two stages: pre-crack initiation and post-crack initiation,and the force of the contact area between the crack expansion device and the rock pore wall is simplified as a plane problem.Based on the elastic mechanics,the stress field and displacement field of the area near the hole are analyzed when the rock is subjected to uniform load in the hole.Based on the linear elastic fracture theory,the stress intensity factor and tip opening displacement of crack tip were analyzed,and the relationship between crack width and crack length was established.According to the energy criterion of fracture mechanics,the mechanism of burst energy is deduced,and the relationship among the fracture energy,the input energy of hydraulic fracturing breaking rock system and the elastic energy of rock is established.According to the research content,combined with the actual situation,a small scale swelling and cracking test platform is built.Bluestone with high hardness was selected as the experimental rock sample and the mechanical property parameters were determined.Based on the cohesive force element method,the finite element model of burst rock fracture was established,and the tensile and compressive load characteristics and crack morphology of the model were verified.The validity of the finite element model of burst rock fracture was verified by comparing the pressure curve and fall rock morphology of simulation and experiment.Through confining pressure simulation,the influence of lateral confining pressure on single free surface single hole burst is analyzed,and it is proved that the test law obtained by small scale test is suitable for the actual drilling growth condition.The law of burst pressure,the law of crack development,the law of stress evolution and the law of burst energy corresponding to the change of burst force are analyzed by simulation.Based on the small scale hydraulic fracturing breaking rock test bench,the rock breaking test with single hole and single free plane under pressure relief conditions was carried out,and the single factor test of bursting parameters was carried out.The response surface test was carried out on the key factors selected by the single factor test,and the parameter prediction model of bursting and breaking rock was initially established.Single factor tests were carried out on four parameters,namely,hole edge distance,hole depth,fin length and fin diameter of the crack expansion device.It is found that the factors that have obvious influence on the crack expansion efficiency are hole edge distance and fin length,and the relationship between them and the peak crack pressure and energy of the crack expansion is obtained.The response surface tests of the key factors were carried out,and the interaction of the key factors on the peak bursting force,bursting energy,crack area and falling rock volume was analyzed,and the prediction model of the key factors on the bursting efficiency index was initially established.The stress evolution and crack evolution of hydraulic fracturing breaking rock,intersecting free surface burst and central free surface ring burst were analyzed by plane simulation.The change rule of burst force of different hole number and different free surface Angle was obtained.The method of free surface pressure relief for central free surface ring burst was proposed.The crack profiles of the free surface at different depths were analyzed by three-dimensional simulation,and the optimal depth of the free surface was greater than the length of the blade and less than the depth of the crack.The crack profile control technology was studied by experiments.Three schemes were used to crack rectangular and circular profiles,and ideal peripheral crack profiles and bottom crack profiles were obtained.According to the experimental and simulation results,the hole layout scheme of random roadway burst construction is proposed,and the technology is explained through the burst contour control test. |
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