Rock Fragmentation Characteristics by TBM Cutting and Efficiency under Bi-Lateral Confinement

Abstract

Abstract:In this study, the mechanisms of rock breakage are assessed using tunnel boring machine (TBM) disc cutters under bi-axial pressure. Sequential indentation tests were conducted on granite specimens using a tri-axial testing platform. The morphology and volume of the fractured surface were measured and analyzed using a three-dimensional surface profilometer. An analysis of rock breaking growth and efficiency was performed as well. When the minor confining pressure (σ 1 ) is constant, the results show that a larger difference in confining pressure leads to a larger volume of fractured surface, thereafter improving the rock-breaking efficiency even though the penetration energy is enlarged. On the other hand, when the major confining pressure (σ 2 ) is constant, the penetration energy increases proportionally with the σ 1 ; however, the volume of fractured surface is decreased, and the breaking efficiency is attenuated as well.

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

“…e governing factor for the critical value was however not identified in the study, and only one CCS disc cutter was adopted in the tests. Chen and Song [29] studied the confining stresses' influence on penetration energy, which is calculated by integrating the thrust force with indentation displacement. e penetration energy continuously increased with the rising of confining stresses [29].…”

“…Chen and Song [29] studied the confining stresses' influence on penetration energy, which is calculated by integrating the thrust force with indentation displacement. e penetration energy continuously increased with the rising of confining stresses [29]. However, only a CCS disc cutter was utilized in the tests.…”