Cutting parameter optimization for one-step shaft excavation technique based on parallel cutting method |
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Authors: | Qi-yue LI Kai LIU Xi-bing LI Ze-wei WANG Lei WENG |
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Affiliation: | 1. School of Resources and Safety Engineering, Central South University, Changsha 410083, China;2. School of Civil Engineering, Wuhan University, Wuhan 430072, China |
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Abstract: | The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters (such as the hole spacing L and the empty hole diameter D) and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress. |
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Keywords: | shaft excavation prime cutting blasting numerical analysis cutting parameter optimization loading rate |
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