The Influence of Confining Stresses on Rock Fragmentation, Thrust Force, and Penetration Energy in Sandstone Indentation Tests Using Disc Cutters

Abstract

Hard rock Tunnel Boring Machines (TBMs) engaging disc cutters as cutting tools have been employed in considerable underground coal mines to accommodate the requirement of more stone drivage as operations are going deeper. This study conducted a set of disc cutter indentation tests to explore the influence of confining stresses on rock fragmentation, thrust force, and penetration energy on sandstone, which is commonly encountered in underground coal mines. The test results show that there exists a critical confining stress, under which the maximum thrust force and penetration energy keep increasing with confining stress mounting while the maximum thrust force and penetration energy will decrease or flatten if it is surpassed. By combining with previous studies and comparing the critical confining stress values to the rock mechanical properties’ values, the critical value is most likely to be of cohesion. For subsurface rock fragmentation, the Constant Cross Section (CCS) disc cutter indentation has denser cracks and their orientations are more lateral than those under the V shape one; the V shape disc cutter indentation is less sensitive to confining stresses, with no notable increase of crack number and crack reorientation with increasing confinement. Thus, the CCS disc cutter is more favorable than the V shape one from the perspective of rock fragmentation under confining stresses.

Dynamic Rock‐Breaking Process of TBM Disc Cutters and Response Mechanism of Rock Mass Based on Discrete Element

“…e disc cutter, at the foremost end of TBM, is an important part of TBM, which determines whether it can effectively break rock and directly generate load on the surrounding rock to cause dynamic damage to the rock mass. In order to better achieve the destructive effect, the generation, propagation, failure mechanism, and mode transformation of rock cracks have become a hot topic that many scholars pay attention to, and it is of great significance to how to optimize the design of the disc cutter for efficient rock breaking [1][2][3][4][5].…”