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

Abstract

During the blasting excavation of deep underground caverns, the effects of the structural surface on crack propagation are usually considered in addition to the clamping effects of high in situ stress. Based on the notched borehole and timing sequence control (TSC) fracture blasting method, this paper studies the effects of different borehole shapes on the degree of damage of the surrounding rock and profile flatness of the rock anchor beams and the effects of different filled joint characteristics on the blasting crack propagation rules. The results show that the damage depth of the surrounding rocks by round hole smooth blasting is approximately twice that by notched hole smooth blasting, by which the profile formed is flatter. The notched primary borehole (PBH) remains a strong guidance for crack propagation in a rock mass with filled joints, while the stress concentration effects of the round target borehole (TBH) cannot fully guide the cracks until they fall within a certain distance between the PBH and TBH. It is favourable for cracks to propagate along the lines between boreholes with larger filled joint strengths and larger angles between boreholes.

The Role of Delays in the Performance of Blasting

“…[21] considered the initiation sequence of a row of holes: one-directional initiation vs. initiating the row from the extremities towards the center: the order of ignition of blast holes is from the center to both ends of the row of blast holes can produce a more uniform size of fragmented rocks. Also [22] discuss fracture creation, considering also rock mass joints: for simultaneous holes they state that cracks propagate along the lines between boreholes with larger filled joint strengths. [23]Yin et al, (2021) study crack formation and damage to the surrounding rock could considering shaped charge form and short time delay blasting scheme.…”