Numerical Simulation on Selection of Optimal Delay Time for Precise Delay Blasting

Abstract

In the traditional presplitting blasting, the presplit holes are generally uniformly initiated, which causes local damage to the retained rock mass while forming the damping ditch. In order to determine the optimal delay time of the precise delay initiation hole by hole, the finite element software ANSYS/LS-DYNA is used to build a blasting model of the concrete, which includes concrete, explosive, and air to simulate the crack forming process of the presplitting hole under various initiation modes. Four kinds of initiation modes for blasting, namely, simultaneous initiation with 0 ms, 9 ms, 12 ms, and 15 ms of delay between adjacent holes, are set up to determine the exact delay time of the best presplitting effect. The simulation results show that when the prehole detonates simultaneously, the inner hole crack penetrates the fastest, but the peak stress around the hole is up to 147.9 MPa. When interhole delayed initiation is used, although the time of interhole crack penetration is prolonged, the stress coupling is generated around the precrack and the maximum stress is obviously reduced. The maximum stress generated under the three delayed initiation conditions is only 76.8 MPa. Considering the requirement of damage control of surrounding rock mass and the rapid formation of precrack, 9 ms delay time is determined as the precise delay time of this test.

Experimental and Numerical Study on the Effect of Three-Hole Simultaneous Blasting Technology on Open-Pit Mine Bench Blasting

“…(2) Reducing the ratio of large blocks As mentioned above, the three holes within the same section were detonated simultaneously. In this case, the distribution of charge was relatively extensive, and the explosive load borne by the rock mass was relatively uniform [2,19]. This enabled sufficient fragmentation of the rock mass.…”

“…Due to its relatively low cost and high efficiency [1,2], blasting technology is widely adopted in various engineering applications across a wide range of domains, such as mining, transport infrastructure construction, and building demolition [3][4][5]. In recent years, a large number of new blasting equipment has entered the blasting industry, among which the digital electronic detonator has been highly recognized by many researchers and users due to its simple operation, high delay accuracy, and detectable blasting network [6,7].…”

A Comprehensive Review of Traditional, Modern and Advanced Presplit Drilling and Blasting in the Mining and Construction Industries

“…An important aspect of the analysis of blasting mechanics is the numerical simulation of the blasting process. One of the most effective methods, LS-DYNA3D, is used to analyse the nonlinear dynamic questions, such as stress propagation and crack evolution characteristics, in order to study the deephole presplit cracking mechanism with an empty hole [36]. Numerical model takes the model test as the prototype, which consists of three components: air, explosives, and concrete.…”

“…Figure 4 Near-zone damage nephogram of a blasting model with different delay times [36] Modelling and grid specification Following simulations by Chen et al [4], this modelling and grid meshing were devised based on Cartesian theory. A 50 mm-diameter explosive cylinder and 0.1 m x 0.1 m rock rectangles were used in the model's centre to refine the grid.…”