Analysis Of Influencing Factors On Propagation Of Blasting Cracks In Deep Rock Mass

In recent years,due to the depletion of shallow resources,both at home and abroad have begun to develop in the direction of exploiting deep resources.The destruction of deep rock mass is the result of the combined action of high ground stress and explosive impact load.However,when the deep high-stress rock mass is blasted,the blasting result of the deep rock mass will be very different from that of the shallow rock mass.Therefore,it is of great practical engineering significance to study the influence of in-situ stress on deep rock burst fracture lines.In this paper,the implicit-explicit algorithm in LS-DYNA is used to simulate the expansion process of burst lines under ground stress.In this paper,through theoretical analysis and numerical calculation methods,the blasting crack pattern under the action of ground stress is simulated,and the influence of blasting stress wave is simulated and analyzed.The main work of this paper and the research results obtained are as follows:(1)Based on the LS-DYNA software,a rock single-hole blasting model under insitu stress conditions is established,and the influence of different in-situ stresses and unequal two-way in-situ stresses on the expansion of blast cracks is studied.The study found that the magnitude of the ground stress has a great influence on the expansion of the burst pattern.With the increase of the ground stress,the length of the burst pattern decreases;under the condition of unequal two-way ground stress,the expansion direction of the burst pattern is affected the most by the ground stress.Influence of stress direction;ground stress inhibits the peak velocity at the near point of the blast hole,and enhances the peak velocity at the far point of the blast hole,and this effect becomes more significant as the ground stress increases;unequal ground stress Under the conditions,the stress in the vertical direction and the horizontal direction will be different,but the stress value increases with the increase of the ground stress.(2)The expansion process of tunnel blasting cracks under ground stress conditions is simulated.The influence of voids on the expansion of burst lines is studied by the method of combining theory and simulation.The simulation results show that when there are voids between the blasting holes of tunnel blasting,the cracks between the blasting holes and the voids pass through as follows: After the explosive is detonated,the cracks at the explosive hole first expand outward,and when the stress wave reaches the voids When a certain amount of energy accumulates in the hole,cracks do not occur immediately at the hole,but start to crack when a certain amount of energy accumulates at the hole.After that,the main crack extending from the explosive hole penetrates the crack extending from the hollow hole.At the same time,the greater the ground stress,the more difficult it is to form the crack contour line between the two blast holes and the void.(3)Using the implicit-explicit algorithm of LS-DYNA,the whole process of the expansion of the double-hole millisecond blasting crack pattern under ground stress is simulated.The research results show that: the difference of the differential time will affect the peak velocity and the stress of the particle in the middle of the two holes.At the same time,the millisecond blasting will increase the degree of fragmentation between the two blast holes.