Dynamic Indentation Characteristics for Various Spacings and Indentation Depths: A Study Based on Laboratory and Numerical Tests

Abstract

Laboratory and numerical study tests were conducted to investigate the dynamic indentation characteristics for various spacings and indentation depths. First, laboratory tests indicate that the increase in the indentation depth first resulted in enlarged groove volumes, caused by fiercer rock breakages between indentations for a fixed spacing; then, the groove volume slightly increased for further increase in indentation depth, whereas the increase in spacing restrained rock breakages and resulted in shrunken grooves. In addition, the numerical study agreed well with laboratory tests that small chips formed at the shallow part of the rock specimen at the early indentation stage, and then, larger chips formed by the crack propagation at deeper parts of the rock specimens when the indentation depth increased. With further increase in indentation depth, crushed powders instead of chips formed. Moreover, the numerical analysis indicates that crack propagation usually leads to the decrease of the indentation force and the dissipation of the stress concentrations at crack tips, whereas the cessation of crack propagation frequently resulted in the increase of the indentation force and the stress concentrations at crack tip with the increase in indentation depth.

Stress Evolution in Punch-Through Shear Tests: A Numerical Study Based on Discrete Element Method

“…However, the crack propagation sequence is still unclear. The previous studies [26][27][28] show that the stress evolution relates to the crack development. According to the comparisons on the axial compression force and the fracture pattern between laboratory and numerical results, we may infer that the stress evolution may relate to the crack development and the fluctuations in axial compression force.…”

“…Especially, among these methods, the discrete element method can record the crack development [23][24][25]. Thus, with the recent studies, using the measure circle logic to study stress evolution characteristics [15,[26][27][28], we applied Particle Flow Code 2D (PFC 2D) to relate the stress evolution to crack development in the punch-through tests.…”

Multiobjective Optimization Design for Structural Parameters of TBM Disc Cutter Rings Based on FAHP and SAMPGA

“…With the rapid development of tunnel constructions, tunnel boring machines (TBMs) are widely employed in tunnel excavation due to their high excavation efficiency, excellent safety, and less ground disturbance [1,2]. Disc cutters mounted on TBM cutterhead are the main rock breaking tools, and cutter rings interact with and cut rocks directly during the TBM tunneling process [3,4]. When tunneling in the complex and harsh geological conditions, the cutter ring suffers from high contact stress and strong impact vibration.…”