Model Test on Failure Modes of Anchorage Tunnels Subjected to Blast Loading

Abstract

The premise of anti-explosion reinforcement design of underground tunnels is to find out the failure form and failure mechanism of anchorage tunnels to take targeted reinforcement measure sunder explosion load. However, the antiexplosion reinforcement effect of bolts(cables) on underground tunnels is seldom studied at present, and the failure law of tunnels is not clear, which cannot provide scientific basis for anti-explosion reinforcement design. In view of this, the model test apparatus for anti-explosion structures in geotechnical engineering and explosive load simulation test technology were firstly developed in this study, and based on Froude similarity theory, a series of anti-explosion model tests on different anchorage tunnels subjected to blast loads, including plane charge and mass charge, were carried out. The failure modes of several kinds of anchorage tunnels under explosion loads were obtained. Some conclusions were drawn from the model test results. Under the same test conditions, spalling occurs in tunnel roof in the plane charge test, while shear cracks and stagger cracks occur in tunnel spandrel in the mass charge test. The anti-explosion capacity of the tunnel reinforced by full-grouted bolts is better than that by part-grouted bolts. The augmentation of bolt length has no control effect on preventing crack extension in surrounding rock, when bolt spacing decreases to a certain density, it just prevents cracks from extending into the reinforced region. The local and dense lengthening bolts in tunnel spandrel can prevent or interdict cracks from extending in surrounding rock, or compel cracks to detour the reinforced region; consequently, it can enhance anti-explosion capacity of the tunnel. This study provides a significant reference for improving reinforcement measures of the underground anti-explosion structures and its anti-explosion capacity.

Distribution of cracks in an anchored cavern under blast load based on cohesive elements

“…Scholars have investigated the failure modes of underground anchored caverns without pre-existing fractures. Xu et al 5 and Wang et al 6 investigated the failure of anchored caverns under blast load through physical model testing. Sivalingam et al 7 surveyed the stress redistribution around adjacent tunnels during blasting excavation.…”

Distribution of Cracks in an Anchored Cavern Under Blast Load Based on Cohesive Elements

“…Scholars have investigated the failure modes of underground anchored caverns without pre-existing fractures. Xu et al [5] and Wang et al [6] investigated the failure of anchored caverns under blast load through physical model testing. Sivalingam et al [7] surveyed the stress redistribution around adjacent tunnels during blasting excavation.…”