Pull-out characteristics of rock bolts under the influence of “natural” coupled fractures

IF 2.8 3区 工程技术 Q1 MATHEMATICS, INTERDISCIPLINARY APPLICATIONS
Hao Shi, Wenlong Chen, Houquan Zhang, Xuepeng Zhang, Lei Song, Ming Li, Linlin Liu
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Abstract

This study investigates the pull-out characteristics of rock bolts with “natural” fractures induced by coupled dynamic-static load, which is imperative for assessing the stability of engineering structures and averting engineering disasters. “Natural” fractures under dynamic-static coupled load were simulated using a biaxial compression model and a SHPB model utilizing the PFC2D software. These coupling fractures were then incorporated into the bolt pull-out model after extraction and amplification. The impacts of these fractures on bolt’s anti pull-out properties and the related micro-mechanical mechanism of bolt-rock interaction were analyzed. The results are as following: (1) The axial bolt load peak value, new crack numbers, and AE event peak values generally decrease as the pull-out specimen’s damage degree increases. There’s a critical threshold for impact damage affecting the bolt’s pull-out characteristics, indicating that significant structural failure of the pull-out specimen must occur for notable changes in bolt pull-out characteristics. (2) The bolt’s peak axial load declines with increasing fracture numbers and impact time and is weakly related to the peak displacement. Bolt tensile stiffness decreases with the rise in fracture number, biaxial compression confining pressure, and impact time. (3) The contact force accumulation within the rock mass evolves from a layered to a networked form as confining pressure increases. The distribution number of dynamic load-induced fractures directly impacts the rock mass’s loading area and contact force transfer path. (4) The magnitude of normal and tangential contact forces is positively correlated with the load level. Rapid changes in particle’s indirect contact force lead to a certain deviation in the distribution direction of normal and tangential contact forces during the post-peak phase.

“自然”耦合裂缝影响下锚杆拉拔特性
研究动-静耦合作用下具有“天然”裂隙的锚杆的抗拔特性,对评估工程结构的稳定性和避免工程灾害具有重要意义。利用PFC2D软件,采用双轴压缩模型和SHPB模型对动静耦合载荷下的“天然”裂缝进行了模拟。在提取和放大后,将这些耦合裂缝纳入锚杆拔出模型。分析了这些裂缝对锚杆抗拔性能的影响以及锚杆-岩石相互作用的微观力学机制。结果表明:(1)随着拉拔试件损伤程度的增加,轴向锚杆荷载峰值、新裂纹数和声发射事件峰值普遍减小。冲击损伤对锚杆拔离特性的影响存在一个临界阈值,说明拔离试样发生重大结构破坏后,锚杆拔离特性才会发生显著变化。(2)锚杆峰值轴向载荷随断裂次数和冲击时间的增加而减小,与峰值位移的相关性较弱。锚杆抗拉刚度随断裂次数、双轴压缩围压和冲击时间的增加而减小。(3)随着围压的增大,岩体内部的接触力积累由层状向网状演化。动载裂隙的分布数量直接影响岩体的加载面积和接触力传递路径。(4)法向接触力和切向接触力的大小与荷载水平呈正相关。颗粒间接接触力的快速变化导致峰后阶段法向和切向接触力的分布方向出现一定偏差。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Computational Particle Mechanics
Computational Particle Mechanics Mathematics-Computational Mathematics
CiteScore
5.70
自引率
9.10%
发文量
75
期刊介绍: GENERAL OBJECTIVES: Computational Particle Mechanics (CPM) is a quarterly journal with the goal of publishing full-length original articles addressing the modeling and simulation of systems involving particles and particle methods. The goal is to enhance communication among researchers in the applied sciences who use "particles'''' in one form or another in their research. SPECIFIC OBJECTIVES: Particle-based materials and numerical methods have become wide-spread in the natural and applied sciences, engineering, biology. The term "particle methods/mechanics'''' has now come to imply several different things to researchers in the 21st century, including: (a) Particles as a physical unit in granular media, particulate flows, plasmas, swarms, etc., (b) Particles representing material phases in continua at the meso-, micro-and nano-scale and (c) Particles as a discretization unit in continua and discontinua in numerical methods such as Discrete Element Methods (DEM), Particle Finite Element Methods (PFEM), Molecular Dynamics (MD), and Smoothed Particle Hydrodynamics (SPH), to name a few.
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