| In recent years,with the continuous development of economy and science and technology,blasting engineering technology has also been developed.Bench blasting is widely used in mining,water conservancy,hydropower,earthwork excavation,construction and other fields.The effect of bench blasting is affected by many factors.Reasonable millisecond delay time can effectively reduce the vibration caused by blasting,and different initiation sequence can also produce blasting effect.In order to improve the engineering quality of bench blasting,this paper mainly studies the influence of different initiation sequence on bench millisecond blasting.By means of finite element analysis software ANSYS/LS-DYNA,the rock blasting process of forward initiation,reverse initiation and intermediate initiation of single-row and three-hole bench blasting is numerically simulated,and the effects of different initiation sequence on the stress propagation law of rock blasting are studied by comparing the millisecond blasting of step-by-hole blasting with that of full-initiation,first initiation of intermediate blasting and simultaneous initiation of two side blasting holes.The main contents and conclusions are as follows:(1)Using ANSYS/LS-DYNA software to carry out numerical simulation,the forward initiation,reverse initiation and intermediate initiation of LS-DYNA with HJC material constitutive model and high-energy explosive are simulated respectively,and the stress propagation law,vibration velocity and displacement change of these three initiation modes are compared and analyzed respectively.The results show that the stress and velocity produced by reverse initiation are the largest and the attenuation is the fastest,followed by intermediate initiation,and the stress and velocity produced by forward initiation are the smallest and the attenuation is the slowest.For items requiring more stringent blasting vibration,forward initiation can be adopted;the displacement produced by different initiation modes in the middle of the grain is the largest and the intermediate initiation is more conducive to rock fragmentation.(2)Based on millisecond millisecond delay blasting theory,finite element analysis software is used to simulate and study the stress changes during the detonation process of step-by-hole initiation,middle-hole initiation,simultaneous initiation and simultaneous blasting of both sides of the blasting holes,and the propagation law of stress wave,as well as the vibration speed and displacement are compared and analyzed.The results show that the maximum effective stress and vibration velocity are generated by homogeneous initiation,and the minimum effective stress is generated by hole-by-hole initiation.Compared with homogeneous initiation,the velocity of hole-by-hole initiation decreases by 51.15%,the velocity of both sides initiation decreases by 32.82%,and the effect of hole-by-hole initiation is better.The displacement of hole-by-hole initiation is the largest,and the displacement of intermediate hole initiation is the smallest.Not conducive to rock fragmentation and throwing.(3)The vibration data of step millisecond blasting with different initiation sequence are compared with numerical simulation.The results show that the vibration produced by hole-by-hole initiation is smaller than that by hole initiation and simultaneous initiation,and the blasting effect is better,which is conducive to vibration reduction. |
