Understanding parameters impacting the mechanism leading to spalling around underground excavations in massive rocks under high stress

Abstract

Underground excavation is required for mining engineering and nuclear waste repository. As the excavation progresses, the stress increases, and brittle failures frequently exist. Brittle failures are arranged into two types: spalling and rock bursting. Spalling in the shape of a V-notch may severely damage the machine and workers involved in its development. This potential hazard can be mitigated by fully representing all parameters that cause spalling in the model. Thus, optimized tunnel design can be achieved. As a result, the company can strike a balance between profit and safety. Several possible results can be proposed by conducting a series of sensitivity studies on a credible model based on a real-world case study of spalling in the Underground Research Laboratory (URL) in Canada. It includes predicting the Depth of Failure (DOF) of spalling by changing two main parameters, particularly strength (tensile and crack initiation) and stress (σ1). The result reveals that increasing tensile strength over UCS decreases DOF, increasing percentages of crack initiation (CI) over UCS decreases DOF, and increasing σmax over UCS increases DOF. Moreover, systematic errors in the generated model can lead to inaccurate DOF estimation. This problem must be approached with engineering judgment in order for the solution to correspond to the actual spalling phenomenon.