Abstract
Large-scale testing of SCDA Performance under confinement
Tuo Chen*, Isaac Vennes, Hani Mitri
Soundless chemical demolition agents (SCDA) are powdery cementitious materials, which upon mixing with water and being poured into a confined borehole, generate high pressure causing the destruction of the surrounding material. The implementation of SCDA has advantages over the traditional drilling and blasting method for rock fragmentation, such as reducing greenhouse gas emissions, no vibration, and lowering the cost of ventilation and rock supports. However, few attempts have been done on applying SCDA in underground mines as the presence of hard rock and high in-situ stress. This study will explore the potential application of SCDA performance on underground mining excavations, which is part of a multi-phase project aiming to revolutionize an alternative, explosive-free method for rock breakage in underground mines.
In this work, a modelling methodology is firstly proposed to simulate rock breakage under loading conditions using discrete-element code PFC2D/3D. The fractures induced by SCDA expansion under uniaxial loading are simulated explicitly in PFC3D code. The simulated fracturing direction is the same as the observation from the uniaxial test, corresponding to the maximum principal stress direction, proving that PFC code is capable of modelling pressure and volume change of SCDA by assuming a cylinder wall with an increased radius. Then, PFC2D code is used to model SCDA performance under biaxial loading. Various panels with different borehole patterns are examined in PFC2D model. Modelling results indicate that the uniaxial stress relief pattern is not sufficient for SCDA to break the panel. The pattern will only break when applying biaxial stress relief pattern. Two panels are eventually selected and tested in the large-scale tests under confinement to validate the modelling results. The test results show that the modelling results are in line with large-scale tests, proving the PFC code can be used to optimize the borehole pattern under confinement. Also, the large-scale tests show the promise of implementing SCDA for hard rock excavation under high in-situ stress in underground mines.