Meso response mechanism of diorite under loading and unloading conditions

doi:10.16265/j.cnki.issn1003-3033.2026.03.1000

Abstract

Abstract:

In order to explore the microscopic response characteristics of hard rock under the loading and unloading stress paths, the diorite numerical model under 20 MPa confining pressure was carried out by using the PFC^3D program. Then, the numerical simulation results were compared with the laboratory test results to verify the reliability of the numerical simulation scheme. On this basis, the change characteristics of micro particle velocity, contact force and tensile shear micro-crack along the axial and radial direction of the model during loading and unloading were studied. The results show that in the pre-peak stage, driven by synergistic effects of terminal energy input and lateral confinement, particle axial velocity exhibits higher values at the ends and lower values in the central region, while radial velocity increases linearly from interior to exterior. Contact normal forces demonstrate enhanced distribution characteristics along both axial (ends > center) and radial (periphery > core) directions, with sustained growth during loading. Tensile cracks dominate damage initiation, concentrating radially near unloading surfaces while distributing uniformly axially. In the post-peak stage, an abrupt reduction of lateral confinement triggers a dramatic particle velocity surge. Disintegration of force chains precipitates rapid decay in contact normal and shear forces. Accelerated propagation of tensile-shear micro-cracks occurs at the mesoscopic level, particularly with shear cracks concentrating and coalescing along double-shear planes, directly precipitating macroscopic bearing-capacity collapse.

Key words: loading and unloading condition, diorite, microscopic, numerical simulation, distribution characteristics

CLC Number:

X915.5

AN Xuexu, HU Zhiping, WANG Zhenlin, TIAN An'an, ZHANG Yonghui. Meso response mechanism of diorite under loading and unloading conditions[J]. China Safety Science Journal, 2026, 36(3): 221-228.

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参数	量值	参数	量值
最小半径/m	0.000 6	摩擦因数	0.001
粒径比	2.50	内摩擦角/(°)	4.5
安装间距/m	0.000 2	颗粒密度/ (kg·m^-3)	2 710
黏结弹性模量/GPa	8.563	黏结张拉强度/MPa	20.02 ± 0.275

围压/MPa	10	20	30	40
试验最大偏应力/MPa (对应轴向应变值/%)	190.274 (1.320)	221.412 (1.485)	243.919 (1.626)	275.674 (1.811)
数值最大偏应力/MPa (对应轴向应变值/%)	185.511 (1.337)	222.051 (1.527)	248.520 (1.633)	280.871 (1.872)
相对强度误差/% (相对轴向应变误差/%)	2.503 (1.288)	0.289 (2.828)	1.886 (0.431)	1.885 (3.368)