| At present,the drilling and blasting method is mainly used in domestic rock roadway excavation.However,there are some main problems in the drilling and blasting method,such as poor controllability of rock road wall rock instability,low safety and complex technology.Based on the fact that the tensile strength of the rock is much smaller than the compressive strength,a method of hydraulic fracturing rock breaking is proposed.This method has the characteristics of small damage to the surrounding rock,high efficiency and strong controllability,and is particularly suitable for breaking hard rock.This paper mainly studies directional fracturing and breaking rock from three aspects: fracturing and breaking rock theory,fracturing and breaking rock test and numerical simulation,and fracturing and breaking rock under the action of holes.Based on the Griffith crack propagation criterion,the crack propagation theory of the rock is analyzed,and the fracture mechanics model of the rupture rock is established based on fracture mechanics.The fracture formation mechanism and the design parameters of the rupture rock are analyzed.Based on the theory,a superimposed model of the stress field around the cavities was constructed,and the distribution of the stress field around the cavities was analyzed.Based on the rock fracturing process and the power output characteristics of the rock fracturing device,a finite element model of the rock fracturing was established.The mechanism of action of the rock was studied.According to the test content and purpose of this subject,a drill-up test bench was built,and the mechanical properties of the three artificial rock samples and bluestone were tested;The drill-up test rig conducts research on the mechanical characteristics of rock samples,the loading method and size of confining pressure,and the effect of borehole margin on the performance of rock fracturing,and analyzes the effects of various factors on the rock fracturing effect and the trend of the rock fracturing pressure curve.The influence of the fluctuation pressure of the fracturing pressure is compared and analyzed.The rock fracturing effect and the variation law of the fracturing pressure under the two confining pressure loading methods and the drilling margin are compared and analyzed.According to the actual working conditions,the simulation model of rock fracture is established,and the simulation model of rock fracture is verified.Based on the Mohr Coulomb criterion,the stress distribution of the rock under confining pressure is analyzed,and the rock compressive strength and shear strength are obtained.The shear strength will increase with the increase of confining pressure.The change state of rock stress and strain during the process of rock expansion and fracturing is studied,and the relationship between stress and strain during the crack propagation process is analyzed.Explored the changes of rock cracks and fracturing pressures with the drilling margin,and the distribution state of circumferential stress on the wall of fracturing holes under the action of fracturing force is analyzed.Based on the stress concentration effect of the hole,its mechanical model was established,and the stress distribution state near the hole was analyzed;The change process of rock stress and strain under the action of holes was studied,and the variation law of rock fracturing pressure and crack propagation under different hole angles were explored,and the critical angle of 45° for the hole-assisted directional fracturing rock was obtained;The effectiveness of the hole effect was verified,and the effect of the presence and absence of holes on the fractured rock breaking results was qualitatively and quantitatively analyzed.Experimental studies were conducted on the effects of the hole distance and the number of holes on the fractured rock breaking performance.The relationship between the distance and the number of pores on the rock fracturing effect,the process of the fracturing pressure curve and the change law of the fracturing pressure.The paper has 85 figures,7 tables,and 128 references. |
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