Study On The Directional Fracturing Mechanism Of Rock Blasting With Water Jet Slotting Assisted

In the process of blasting excavation construction for underground engineering,the effective control of the explosive energy and the directional fracture of the rock is the eternal purpose of engineers.To achieve this goal,a wide range of directional fracture blasting techniques have been developed.High pressure water jet guided smooth blasting technology was proposed because of its unique advantages for cutting.This technology can effectively avoid the drawbacks in the traditional mechanical groove blasting process,thus it has a brighter prospect in applications.However,the mechanism of the directional blasting guided by high-pressure water jet slot-cutting technology still remains unclear;and the gap in the effects of the various rock defects on the directional fracture needs to be filled.These deficiencies have greatly limited the development of this technology.To make a contribution to revealing the mechanism of the directional blasting guided by high-pressure water jet slot-cutting,this article conducted a systemic research based on the national key basic research project and the national security supervision and administration of "four of a batch of" key technology research project.The results are as follows:(1)The propagation mechanism of internal stress wave in the slotted blast hole was analyzed according to the theory of stress wave and the dynamics of blast shock;the energy gathering effect of the explosion stress wave at the slot made by waterjet was studied.The theoretical calculation formula of the extreme stress on the stress strengthening line was proposed and the mechanism of effects of the waterjet slot on the characteristics of the initial crack generation was stated.Based on the elastic-plastic fracture mechanics theory,cracking properties of slot tip was analyzed under the influence of quasi static of a critical raw gas jet,which further reveals the mechanism of directional fracture assisted by jet slotting under blasting load.(2)The mechanism of the effects of natural fractures on the propagation features of blast shock was analyzed and the interaction model between them was established.The effects of natural fractures of different directions and distances on the distribution features and dynamic strain evolution characteristics of burst cracks were experimentally studied.The explosion stress distribution and evolution law was numerical studied.And the mechanism of the effects of natural fractures on the cracking of rock burst assisted by waterjet was obtained.(3)The acoustic emission characteristics and the crack propagation law of double boreholes blasting was studied,and the evolution law of explosion stress field distribution was also analyzed by numerical simulation,then the mechanical parameters was obtained.(4)The law of crack propagation influenced by the normal circular empty hole and the slotted empty hole under blasting load was studied;the explosive stress wave propagation law and distribution regularity of crack under the effects of single slotting hole and double slotting holes of different types and different spacing of the empty hole were numerical analyzed;As a result,the mechanism of slotted empty hole for guiding the blasting crack propagation was revealed.The results,to some extent,can enrich the theory of directional fracture of rock aided by jet slotting,and provide evidence for the practical applications and parameter optimizations of the directional blasting guided by high-pressure water jet slot-cutting technology.