| Cumulative blasting as the main technical means to enhance the explosives work capacity.The explosive energy has the characteristics of high concentration,strong directional and destructive force.The principle is to use a specific charge structure to make the explosive blasting cumulative effect.Cumulative blasting technology can be used in actual blasting projects to achieve cost savings,reduce labor consumption and improve work efficiency.However,it is difficult to be widely used in the field of industrial blasting because of the complicated construction process and restricted application conditions during the construction process.This paper proposes a symmetrical bilinear initiation(SBI)method based on the theory of collisional clustering of blast waves,which is characterized by simple operation,high utilization rate of the borehole and low block rate after blasting.In this paper,the two-dimensional planar blast wave propagation characteristics of column charges are investigated through a combination of theoretical analysis,numerical simulation and standard tests.The main research of the paper includes the following aspects.Firstly,the dynamics of rock crushing mechanism and blasting load on rock crushing are studied.Combining several rock crushing theories,the calculation method of the damage range of different regions of the rock during the crushing process and the effect of different strain rates on the strength of the rock in the damage region are analyzed.At the same time,the burst pressure growth curves at different stages are obtained by means of theoretical analysis of the burst wave collision aggregation mode.The change law of the burst pressure after the burst wave collision is obtained.The results show that the use of SBI method,the blast wave collision inside the explosive,to achieve Mach reflection conditions when the blast pressure growth can reach more than three times.Secondly,a set of Holmquist-Johnson-Cook(HJC)rock ontological parameters were obtained using theoretical calculations and empirical extrapolation.Finite Element Method(FEM)software was used to analyze the rock crack expansion pattern under different in-situ stress conditions when the SBI method was used.The simulation results show that the SBI method can effectively increase the explosive internal blast pressure,forming local energy aggregation,and then promote the expansion of rock crack;in-situ stress has a inhibitory effect on crack expansion,the greater the inhibition of in-situ stress is more significant,the size of the crush zone decreases with the increase of in-situ stress.And the study of the two-dimensional planar blast wave propagation characteristics of the strip package with the height of the charge,the diameter of the charge roll and the detonation method of change in law.Finally,based on theoretical calculations and numerical simulations,lead block tests to measure the work capacity of explosives and experimental research on pit blasting with the application of blast wave collision clustering process are carried out.Lead cylinder test results show that the SBI method compared to the center point detonation method explosive work capacity can be increased by 14.5%.Soil pit blasting test results show that the blast wave collision can effectively improve the effect of local energy concentration of explosives,in the non-detonation direction of the explosive is more conducive to the penetration between the pit. |
