| Deep mineral resources mining under the influence of high stress deep rock body is prone to layer cracking,impact ground pressure(rock explosion)and extrusion large deformation and other dynamic disasters.The top-cutting pressure relief technology and deep-hole blasting pressure relief technology,both of which use explosive blasting to form a certain damage fracture zone and supply force release inside the rock body,are important methods for the control of dynamic disasters at present,and the effect of deep-hole blasting becomes the key to the success of the implementation of such methods.In order to explore the residual strength of deep hole blasting damage rock,the crack evolution law inside the rock formation.This paper takes the deep high stress environment overrunning deep hole blasting damage fractured rock body as the research object,and adopts the comprehensive research method of indoor test,theoretical analysis,field test and numerical simulation to study,the main research contents and conclusions include:(1)In order to study the changes of mechanical properties and energy dissipation of sandstone damaged by blasting load under different surrounding pressure,uniaxial and triaxial compression experiments were carried out on sandstone with different damage degrees by using triaxial loading device.The results show that the blasting load reduces the bearing capacity of the rock,and the total energy,elastic deformation energy and dissipation energy of the specimens under blasting load damage are reduced,and the degree of rupture and fragmentation of the specimens increases.In the conventional triaxial compression test,the peak stress and elastic modulus of different damaged specimens increased with the increase of the surrounding pressure,and the total energy,elastic deformation energy and dissipation energy of the specimens increased with the increase of the surrounding pressure,and the total energy,elastic deformation energy and dissipation energy were linearly correlated with the surrounding pressure.The mechanical damage of undamaged specimens increases with the increase of the surrounding pressure,while the mechanical damage of vibration and blast damage specimens decreases with the increase of the surrounding pressure and then increases.(2)In order to investigate the mechanical properties of blast-damaged roof sandstone under the repeated action of disturbing load,the mechanical properties of sandstone specimens with different degrees of damage change during the multi-stage cyclic loading and unloading process.The results show that the multi-stage cyclic loading and unloading will cause secondary damage to sandstone specimens with different damage degrees,and the peak stress will be degraded.The rupture and fragmentation of the specimens at different circumferential pressures decreased and then increased with the increase of the circumferential pressure,and the rupture and fragmentation of the specimens at 0 MPa was the largest and the rupture and fragmentation of the specimens at 5 MPa was the smallest.(3)In order to investigate the microscopic and fine structure changes of blasting damaged sandstone,ultrasonic detector,electronic digital microscope and nuclear magnetic resonance test device were used to analyze the sandstone from microscopic and fine structure of different degrees of damage,the blasting load effect on the sandstone specimen longitudinal wave velocity produced obvious damage,and the closer the location of the blasting point,the higher the degree of damage to the specimen.The blasting load damage specimen apparent appearance along the blasting original surrounding rock body damage,specimen fine structure damage area within a large number of joints,cracks and faults.The porosity of the specimens increased under blasting load damage,and the primary pores of sandstone specimens were mainly microporous and small pores,and the percentage of microporous specimens decreased under blasting load,while the percentage of small,medium and large pores increased.(4)The numerical simulation model of the overlying roof slab was established by GDEM software and combined with the indoor model test to explore the influence law of the gun hole spacing on the blasting effect,and the deformation and damage characteristics of the damaged roof slab sandstone under the action of load were analyzed by the model test.The results show that the stress wave is transmitted to the surrounding area of the roof slab in a fan shape after the blast with the hole spacing of1,2,3 and 4 m.The roof slab unit mainly produces shear damage,and the smaller the hole spacing is,the higher the degree of crack expansion of the roof slab.The damage range of the test block is larger for a 50 mm spacing than for a 70 mm spacing,and the main crack of the test piece is still basically extended along the direction of the shell hole.The blasting damage area should be larger than the blasting vibration area,and the larger the surrounding pressure,the smaller the deformation of the specimen under the same axial pressure.(5)Through numerical simulation and field test,the damage characteristics of overlying rock after advanced deep hole blasting are analyzed.The numerical simulation test results show that with the expansion of the failure in the weakening area,the roof will gradually break,and the connection with the roof in the advancing direction of the working face will be cut off.The roof above the goaf forms a structure with fixed beams at both ends,and the failure of the roof has the characteristics of shear and tensile failure.The bidirectional hole layout makes it easier to penetrate the blasting weakening area to form a complete fracture surface and break the roof.The weakening treatment of the roof in advance can avoid the hidden dangers such as falling and hanging of the hard roof.The field test is based on the mining conditions of230106 working face in Xinji No.2 mine.The blasting parameters are designed and implemented on site,and the effectiveness of the test results is verified by field monitoring.Figure [128] Table [14] Reference [169]... |
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