Study On Fracture Characteristics Of Rock Hole Edge Crack By Static Crushing Agent

The main component of the static crushing agent is calcium oxide,and its volume will expand when it reacts with water,which will exert compressive stress on the inner wall of the borehole,resulting in the cracking and crushing of brittle materials such as rock mass.Static crushing technology has become one of the important methods for rock mass engineering without vibration,coal seam excavation and concrete structure demolition in gas environment by virtue of the environmental protection and safety characteristics of static crushing agent.In this paper,an analytical model of crack initiation and propagation of hole edge crack in rock mass under expansive pressure was established under FRANC2D/L platform,and the theoretical solution was used to verify the model.On this basis,the crack initiation and propagation of hole edge crack were studied.The main contents are as follows:(1)The crack model of the center hole edge in infinite plate provided in the stress intensity factor manual is modified to expand its application range,which provides a basis for subsequent research work.(2)Considering the effect of rock mass static fracture frontage,numerical simulation experiments were used to study the frontage effect of static fracture.The results show that there are two effects on the frontage:(1)Too small resistance line will lead to the deflection of the crack propagation path at the hole edge,and the degree of deflection decreases with the increase of the minimum resistance line.(2)The large resistance line is not conducive to the crack cracking and propagation of the hole edge.(3)The effect of hole spacing on the crack cracking at the edge of the hole is studied.The results show that the smaller the hole spacing is,the more significant the porous effect will be,and the more conducive to crack cracking and ropagation.Based on this,the model of crack initiation and propagation of single hole in infinite plate is modified,and the function analytic formula of correction coefficient considering the porous effect is established,and the calculation model of stress intensity factor of crack initiation and propagation at the edge of porous hole is proposed.(4)On this basis,the propagation law of the pore edge fracture under the simultaneous action of the air front effect and the porous effect is studied.The results show that:(1)Both the cavitation effect and the porous effect can increase the stress field intensity at the crack tip,and both are beneficial to the fracture propagation.(2)Considering the joint action of the surface effect and the porous effect,a calculation model of the stress intensity factor of the hole crack under the joint action of the surface effect and the porous effect is proposed,which provides a theoretical basis for the static fracture design of rock mass materials.