Abstract
A brief literature review of numerical studies on excavation damage zone (EDZ) is conducted to compare the main numerical methods on EDZ studies. A hybrid finite-discrete element method is then proposed to model the EDZ induced by blasts. During the excavation by blasts, the rock mass around the borehole is subjected to dynamic loads, i.e., strong shock waves crushing the adjacent rocks and high-pressure gas expanding cracks. Therefore, the hybrid finite-discrete element method takes into account the transition of the rock from continuum to discontinuum through fracture and fragmentation, the detonation-induced gas expansion and flow through the fractured rock, and the dependence of the rock fracture dynamic behaviour on the loading rates. After that, the hybrid finite-discrete element method is calibrated by modelling the rock failure process in the uniaxial compression strength (UCS) test and Brazilian tensile strength (BTS) test. Finally, the hybrid finite-discrete element method is used to model the excavation process in a deep tunnel. The hybrid finite-discrete element method successfully modelled the stress propagation and the fracture initiation and propagation induced by blasts. The main components of the EDZ are obtained and show good agreements with those well documented in the literature. The influences of the initial gas pressure, in situ stress, and spacing between boreholes are discussed. It is concluded that the hybrid finite-discrete element method is a valuable numerical tool for studying the EDZ induced by blasts in deep tunnels.
Highlights
Blast is widely employed to develop an underground space, such as tunnels, mines, and shafts
Due to the blasting impact, the original state of rock mass around a tunnel is inevitably changed in the form of creation of new fractures, closure and opening of preexisting fractures, and redistribution of stress [1]. e disturbance zone is often referred interchangeably to as excavation damaged zone (EDZ), damaged rock zone (DRZ) [2, 3], or blast-induced damaged zone (BIDZ) [4]
A hybrid finite-discrete element model to be used for modelling excavation damage zone (EDZ) formation process by blasts can include a single discrete element body or a number of interactive discrete bodies, and each of which is of general shape and size and can be discretized into finite elements. e interactions of discrete bodies are model by the discrete element method while the deformability, fracture, and fragmentation of discrete bodies are modelled by the finite element method
Summary
Blast is widely employed to develop an underground space, such as tunnels, mines, and shafts. A combined finite-discrete method, originally proposed by Munjiza [18], was used to study the fracture and fragmentation of rock mass induced by impact loads [13], the fracturing behaviour of unsupported circular excavations in laminated rock masses under various in situ stress conditions [19], and damage process and failure mechanisms around underground openings in clay shales [20]. According to the brief literature review, rare numerical methods are able to model the entire formation process of the blast-induced EDZ, i.e., stress propagation, crack initiation and propagation, and separation, between the newly formed tunnel wall and excavated rock masses. Erefore, in this study, a hybrid finite-discrete element method is employed to model the EDZ formation process in a deep tunnel to gain insight into the rock crack initiation and propagation during excavation by blasts According to the brief literature review, rare numerical methods are able to model the entire formation process of the blast-induced EDZ, i.e., stress propagation, crack initiation and propagation, and separation, between the newly formed tunnel wall and excavated rock masses. erefore, in this study, a hybrid finite-discrete element method is employed to model the EDZ formation process in a deep tunnel to gain insight into the rock crack initiation and propagation during excavation by blasts
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