Abstract
Abstract Free surface-assisted TBM disc cutter for rock breaking is an important direction for the optimizing of TBM cutter structure. To study the influence of free surface on TBM excavation, the free surfaces of limited-width opening and unlimited-width opening were presented, and six different free surface combinations were proposed. The penetration tests of sandstone with different free surface combinations were carried out. The results showed that the rock mass adjacent to the free surface of unlimited-width opening fell off after sample fracture. The rock mass adjacent to the free surface of limited-width opening caused the free surface to close after the rock broke. Under different free surface combinations, the auxiliary effect for rock breaking was not obvious when the free surface depth was shallow, and the failure morphology of the sample changed from vertical splitting to inclined fracture with the increase of free surface depth. The free surface-assisted rock-breaking method can reduce energy consumption during rock breaking. Among all combinations, the cumulative energy before peak load of the SDL sample dropped the most to 37.62% of the intact sample. Finally, the free surface combinations can affect the design of the cutter layout of TBM.
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