Study On The Influence Of Empty Holes On The Rock Breaking Process And Vibration Law In Parallel Diamond Cut Blasting

At present,the drilling and blasting method in China is still one of the most common methods for rock tunneling.The blasting technology is the most important part of the drilling and blasting process.It plays a key role in accelerating the speed of rock tunneling and determines the whole blasting.The blasting effect and tunneling efficiency of the project.Empty holes are often used as the compensation space for the auxiliary free surface and the blasting rock in the diamond-shaped parallel cut blasting,and the empty hole has a great influence on the blasting effect.Based on the analysis of the basic theory of diamond-shaped parallel cut gutters and the rock-breaking mechanism of rock blasting,the finite element analysis software ANSYS/LS-DYNA is used to arrange the hole pattern,the number of empty holes and the empty hole in the actual blasting construction.The numerical simulation and physical model test were carried out on the position and diameter of the hole.The stress wave propagation and crack propagation law at different moments were analyzed,and the pore parameters were optimized.The main research contents and conclusions are as follows:(1)In the constitutive model of LS-DYNA rock material,the HJC model can accurately describe the physical properties of rock under large deformation and high strain;in the HJC constitutive equation,the rock mass is defined in different conditions.Under the stress wave propagation and crack propagation,the damage and failure of the element are shown from the numerical results.It is concluded that the propagation of the explosive stress wave and the crack propagation law in the rock mass are not regular columnar propagation and hoop distribution.Choose the correctness of the constitutive model.(2)Using ANSYS/LS-DYNA software to establish the finite element model,apply the diamond-shaped parallel cut blasting blasting model with different hole pattern,number of empty holes and different empty hole positions to the numerical simulation calculation,and analyze the stress.Wave propagation,crack propagation and the effects of vibration laws.The simulation results show that the cracks formed by the blasting of the diamond-shaped hole are denser and the expansion range is wider than that of the square cloth.The crack development time of the rock mass is fast,the rock mass development is more complete,and the cavity formation effect is better.Guided by the role of cracks and reflection stretching,the pores provide sufficient compensation space for the rock breaking moment to fully break the rock;the pores are too close to the blasthole to form regenerated rock,resulting in energy loss,resulting in low utilization rate of explosives;If the distance between the hole and the blasthole is too large,the crack between the holes will be reduced,and the rock mass in the cavity will be incompletely developed,resulting in a high block rate.This paper proposes that the blasting effect is best when the distance between the hole and the hole is 24cm.The hole utilization rate is high.(3)Through the combination of numerical simulation and physical model test,the influence of the diameter of the pores on the rock-breaking process of the diamond-shaped parallel cut groove blasting is analyzed.The results show that the larger the pore diameter is,the more obvious the stress concentration effect of the pores and the guiding effect on the cracks,the greater the stress value at the pores,and the denser the cracks in the final cavity are formed;At 8mm,small depth of the groove,but the diameter and extent of the failure are large,resulting in a large volume of the final groove cavity.When the diameter of the hole is 16mm,the depth of the groove increases,but the diameter of the fracture decreases,resulting in a small volume of the final cavity.However,the utilization of the blasthole is high and the effect of the grooving is good.The farther the measured point is from the center of the explosion,the smaller the vibration velocity is.The magnitude of the vibration velocity of the measuring point is linear with the diameter of the hole and the larger the diameter of the hole is,the smaller the vibration velocity of each measuring point is.