Numerical Simulation Research of Smooth Wall Blasting Using the Timing Sequence Control Method under Different Primary Blast Hole Shapes

Abstract

To make sure the integrity and stability of surrounding rock structure during blasting excavation of important structural planes in deep underground caverns, two kinds of fine blasting methods, timing sequence control fracture blasting network and notch blast hole, are innovatively combined and the formation of cracks between smooth blasting holes with different delay initiation and different shapes of primary blast holes (PBHs) are compared and analyzed. The results show that when the delay initiation time between the successive explosion holes is greater than or equal to the transverse wave of the PBH propagates to the target blast hole (TBH), the concentrated stress along the connection direction of the hole on the wall of the TBH is larger than the other directions of the hole wall. After the TBH is detonated, cracks will preferentially expand along the connection direction of the blast holes. If the PBH is the notch blast hole, more explosive energy will be directed to the wall of the TBH so that the hole wall along the connection direction of the blast holes will be subjected to greater tension stress before the initiation of the TBH. In this way, the interval between successive holes can be increased and the efficiency of blasting excavation of rock mass can be improved accordingly.

A Study on Cut Blasting with Large Diameter Charges in Hard Rock Roadways

“…In this simulation, the explosive and air were defined as ALE grids, and the Lagrange algorithm was performed for the rock mass and stemming. Using the keyword * CONSTRAINED_LAGRANGE_IN_SOLID, the fluidsolid coupling algorithm was defined to realize the transfer of blasting energy from the detonation products to the rock mass and stemming [38,39]. Nonreflecting boundaries were applied to the model surface in addition to the working face to reduce the influence of stress wave reflections on the simulation results [40,41].…”

WITHDRAWN: Theoretical analysis model and optimization scheme of shape-effect damage in cut blasting

“…Regarding the crack damage evolution of an empty hole in the blasting groove area, Meng et al (2020) established the rock mass damage tension constitutive model plate with LS-DYNA, studied the rock mass damage caused by the empty hole effect, and concluded that the existence of the empty hole significantly improved the tensile stress and stress concentration coefficient near the empty hole. In this work, the stress wave propagation during cut blasting was analyzed, and through dynamic blasting experiments, the bastings in specimens with circular, square and cut holes were analyzed and compared, and the propagation of the corresponding stress waves and explosion cracks were observed (Li et al 2019). Sun et al (2019) determined that the hole arrangement will affect the rock breaking effect of the groove area and determined the most suitable empty hole spacing.…”

Study on timing sequence control fracture blasting excavation of deep rock masses with filled joints

“…Since it takes approximately twice as long to drill a notched hole than a round hole, the construction process of blast excavating the underground powerhouse will be affected. Based on the TSC fracture blasting excavation method proposed by Li 48 , only PBHs are notched in the rock mass model with filled joints; the distance between adjacent boreholes is taken as approximately 19 times the diameter of the boreholes, i.e., 800 mm; the delayed initiation time between PBH and TBH is taken as 1 ms. To compare and analyse the effects of the round target borehole with and without stress concentration effects on the crack propagation, the method in Fig. 10 is used to connect the smooth blasting borehole circuit.…”