| Compared with the current application of the drilling and blasting method and mechanized excavation method face problems such as low footage,low degree of mechanization,high input costs,low efficiency,and large amounts of dust.,hydraulic fracturing breaking rock has an unparalleled advantage.However,there is still little research on cracked rock breaking.This paper mainly uses the methods of theoretical analysis,experimental research,experiment and simulation combined to carry out the research on hydraulically fractured rock breaking.Based on the impact fragmentation experimental equipment,according to the work process and working environment characteristics of the hydraulic fracturing breaking rock,an experimental equipment was built for the research object and content of the project,which mainly includes the drilling system,confining pressure system,fracturing system and test system.Adopting Griffith criterion with I type crack as the model,the crack propagation problem is analyzed based on fracture mechanics and damage mechanics.The simulation of rock fragmentation mechanism under the action of hydraulic fracturing in the process of fracturing breaking rock is carried out.Experimental research on hydraulic fracturing breaking rock is carried out on the hydraulic fracturing experimental equipment,orthogonal experimental design is carried out for four research objects: borehole diameter?borehole depth?borehole margin and rock confining pressure.And through the orthogonal test extreme analysis,the influence sequence and influence trend of the research objects on the rock breaking and breaking rock is obtained.In-depth quantitative analysis of the main factors(borehole margin and rock confining pressure)to get the most reasonable drilling margins and confining pressure,the significance of the factors was determined by the analysis of variance.The 3D simulation model of split wedge-rock-confining pressure is established by using Autodyn simulation software,to simulate the equivalent stress distribution and the process of crack propagation in rock after loading confining pressure,and the stress value of the rock after the rock's internal stress was balanced.The distribution of compressive stress and tensile stress between the contact area and the non-contact area of the wedge and the hole wall under the action of expansion force is studied,and the relationship between the crack propagation path and the stress distribution change process is analyzed.The simulation results are verified and analyzed through the experiment.This paper analyzes the effect of hole on rock strength in theory,and the relationship between the circumferential principal stress and the distance of empty holes on the axis is obtained,and the stress concentration around the hole is local,and the effective range of stress concentration is 5 times hole diameter.The simulation study of hole assistance angle is designed to be 40 degrees,45 degrees and 50 degrees,and the critical angle of hole-assisted directionally fracturing breaking rock is obtained.Finally,the hole-assisted d directionally fracturing breaking rock was verified by experiments.It provides a scientific basis for determining the best angle of hole-assisted directionally fracturing breaking rock. |
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