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...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 MPa 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 45from 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.展开更多
The method of drilling and blasting with explosives is widely used in rock fragmentation applications in the mining industry for mine development and ore production.However,the use of explosives is associated with rig...The method of drilling and blasting with explosives is widely used in rock fragmentation applications in the mining industry for mine development and ore production.However,the use of explosives is associated with rigorous safety and environmental constraints as blasting creates toxic fumes,ground vibrations,and dust.This study is focused on the use of Soundless Chemical Demolition Agents(SCDA)as a more environmentally friendly method for rock breakage and a potential replacement of explosives.In this paper,the results of a series of experimental tests are reported to identify the efect of SCDA on hard rock breakage under no load and under uniaxial loading conditions.Stanstead granite prismatic specimens of 152.4 mm(6″)×152.4–203.2 mm(6–8″)×406.4 mm(16″)are used to test the infuence of borehole size on the time to fracturing with SCDA borehole size of 25.4 mm(1″),31.75 mm(1.25″)and 38.1 mm(1.5″).It is shown that the fracturing time decreases with increasing borehole size.It is also shown that specimens subjected to uniaxial compression of 5 MPa fracture as early as 7 h after SCDA mixing.A borehole spacing to borehole diameter ratio of 12.8 to 14.6 is suggested for practical applications.展开更多
基金supported by a research grant from Natural Resources Canada,Clean Growth Program(Grant No.CGP-17-1003)and industry partner Newmont Corporation.
文摘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 MPa 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 45from 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.
基金supported by a research grant from Natural Resources Canada,Clean Growth Program,Grant No.CGP-17-1003 and industry partner Newmont Corporation。
文摘The method of drilling and blasting with explosives is widely used in rock fragmentation applications in the mining industry for mine development and ore production.However,the use of explosives is associated with rigorous safety and environmental constraints as blasting creates toxic fumes,ground vibrations,and dust.This study is focused on the use of Soundless Chemical Demolition Agents(SCDA)as a more environmentally friendly method for rock breakage and a potential replacement of explosives.In this paper,the results of a series of experimental tests are reported to identify the efect of SCDA on hard rock breakage under no load and under uniaxial loading conditions.Stanstead granite prismatic specimens of 152.4 mm(6″)×152.4–203.2 mm(6–8″)×406.4 mm(16″)are used to test the infuence of borehole size on the time to fracturing with SCDA borehole size of 25.4 mm(1″),31.75 mm(1.25″)and 38.1 mm(1.5″).It is shown that the fracturing time decreases with increasing borehole size.It is also shown that specimens subjected to uniaxial compression of 5 MPa fracture as early as 7 h after SCDA mixing.A borehole spacing to borehole diameter ratio of 12.8 to 14.6 is suggested for practical applications.
