A novel V-cut method for explosive-free breakage of biaxially loaded rock using soundless chemical demolition agents

Abstract

Interest in soundless chemical demolition agents (SCDAs), also known as expansive cements, as potentially viable alternatives to explosives for rock fragmentation, has been growing in recent years. Consequently, there is an increasing amount of literature on the use of SCDA for the breakage of rock blocks and boulders. Limited research has been conducted so far on the breakage of excavation fronts, such as tunnel or drift faces, using SCDA. This is due to the perception that the planar compressive in-situ stresses in the face would inhibit the creation and propagation of fracturing due to expansive pressure. This study proposes a novel V-cut method for demolishing rock panels under biaxial stress using SCDA. This method was examined through large-scale tests and numerical modelling. The rock panels were subjected to high biaxial confinements of 26 and 40 MPa. Such a level of confinement corresponds to an in-situ stress state 1000 m below the surface in the Canadian shield. The V-cut drillhole pattern employs two sets of three SCDA holes angled at 45° from the face of a Stanstead granite panel. The drillhole arrangement aims to create a V-shaped wedge in the plane of major principal stress. When angled drillholes are subjected to expansive pressure, they tend to cast out of the panel face, causing fragmentation. Two panels of 1 m × 1 m × 0.25 m were successfully demolished using the proposed method. The three-dimensional fast Lagrangian analysis code FLAC3D modelling was used to reconstruct the panel failure mechanism owing to the V-cut. This study demonstrates the feasibility of fragmenting an excavation front, such as a rock excavation face, with SCDA using a V-cut drill hole pattern while subjected to high biaxial confinement.