【作者】 王志民；

【导师】 陈仕阔；

【作者基本信息】 西南交通大学 ， 地质工程（专业学位）， 2024， 硕士

【摘要】 岩石和混凝土材料中存在大量非贯通的狭缝或软弱界面,这些缺陷在外部荷载等作用下萌生、扩展和贯通,破坏了材料的完整性并致使其开裂、掉块、破碎,降低了材料的抗变形破坏能力和工程性质,甚至引发严重的工程灾害。岩石等材料内部裂纹的起裂、扩展和贯通破坏的机理一直是岩石力学研究的热点问题,但由于微裂纹本身的复杂性质使其难以被准确表征和描述,以及温度、压力等环境因素的影响,直接对岩石内部的大量微裂纹开展研究将面临巨大挑战,因此开展预制裂纹的类岩石材料的裂纹起裂扩展破坏行为研究具有重要的现实意义。本文采用理论分析、物理试验及有限元数值模拟等方法,基于真/常三轴试验仪开展了内置单裂纹的类岩石材料标准试件单轴压缩试验,基于断裂力学理论,利用有限元数值模拟软件和二次开发平台编写程序模拟计算了预制单、双和多裂纹的标准试件模型的裂纹扩展路径和试件破坏形态,并与物理试验结果、已有文献研究结果对比验证了所提裂纹扩展模拟计算方法的可行性,并将结果推广应用到具体的实际工程中分析危岩的失稳问题。本文主要研究内容如下:（1）通过相似理论与量纲分析,设计了相应的物理模型试验,在试件中预置石蜡圆片制成含单裂纹的类岩石材料标准试件。基于真/常三轴试验仪开展物理力学参数测试,获取原岩和模型试样的材料参数。通过单轴压缩试验得到裂纹扩展路径、试件破坏形态和应力—应变曲线等结果,为数值模拟计算提供参数支持。（2）根据断裂力学及相关理论,提出了基于最大周向应力准则的裂纹扩展模拟计算方法,利用Comsol with Matlab二次开发平台编写程序,对预制单裂纹和双裂纹的标准试件模型在单轴压缩条件下的裂纹扩展路径进行模拟计算。探究了不同裂尖网格划分、裂纹扩展步长和强度折减法的运用对单裂纹扩展模拟结果的影响。（3）综合最大周向应力准则、Ⅰ-Ⅱ复合型裂纹起裂判断方法和Ⅱ型裂纹起裂角数值解,提出了一种Ⅰ-Ⅱ复合型裂纹扩展模拟计算方法,在单裂纹扩展计算中得到了试件的拉-剪复合破裂模拟结果。在此基础上模拟了预制多裂纹的标准试件在单轴压缩条件下的裂纹扩展路径和试件破坏形态,深入揭示了不同K_ⅡC/K_ⅠC值、不同裂纹倾角和不同预制裂纹数对模拟结果的影响。（4）基于提出的Ⅰ-Ⅱ复合型裂纹扩展模拟方法,选取实际工程中的危岩体进行了潜在拉裂式崩塌发育过程的模拟分析,通过在危岩体后缘预制裂缝以表征真实演化过程,模拟计算了自重应力场条件下裂缝的扩展路径和危岩的失稳过程。更多还原

【Abstract】 Rock and concrete materials often contain numerous cracks or weak interfaces.When subjected to external loads,these internal flaws can initiate,propagate and coalesce,destroying the integrity of the material.This can lead to the material splitting,collapsing,and ultimately causing serious engineering disasters.Understanding the mechanism of initiation,propagation and coalescence of cracks in rock and other materials is a crucial topic in rock mechanic’s research.However,due to the complex nature of microcracks,it is difficult to accurately characterize and describe them.Moreover,given the influence of environmental factors such as temperature and pressure,it will pose great challenges to directly study a large number of microcracks in rocks.Therefore,investigating the behavior of crack initiation and propagation in pre-cracked rock-like materials is of great practical significance.This thesis employs theoretical analysis,physical tests and finite element method simulations.Based on the true triaxial test instrument,the uniaxial compression tests were conducted on standard specimens of rock-like material with a prefabricated single crack.Based on the fracture mechanics,programs were developed to simulate the crack propagation path and the failure mode of the standard specimens with prefabricated single,double and multiple cracks using finite element numerical simulation software and a software development platform.The feasibility of the proposed crack propagation simulation method is verified by comparing with the experimental results and the existing literature research results.The simulation methods are applied to the specific practical engineering to analyze the instability of unstable rock.The main contents of this thesis are as follows:（1）According to the similarity theory and the dimensional analysis method,the physical model tests are designed.Based on the true triaxial test instrument,the parameters of the rock and the rock-like sample are obtained.A rock-like material standard specimen,featuring a single crack,was crafted by embedding a paraffin disk within the specimen,followed by conducting a uniaxial compression test.The obtained results,including crack propagation path,failure mode and stress-strain curve of the specimen were obtained,serve as valuable parameters and reference for subsequent numerical simulation calculation.（2）Drawing from the fracture mechanics and related theories,we established a crack propagation simulation calculation method based on the maximum circumferential stress criterion.Using the Comsol with Matlab software develop platform,we developed Matlab programs to simulate the crack propagation path of the standard specimen model with prefabricated single crack or double crack under uniaxial compression.Our investigation explored the effects of different meshing strategies at the crack tip,crack propagation distances,and the implementation of the strength reduction method on simulation results for single crack propagation.（3）Utilizing the maximum circumferential stress criterion alongside,the Ⅰ-Ⅱ mixed mode crack initiation judgment method and the numerical solution of the mode Ⅱ crack initiation angle,we devised a mixed model Ⅰ-Ⅱ cracks propagation simulation method.By applying this method,we obtained simulation results for the propagation of a single crack exhibiting tensile-shear composite fracture behavior.Then we extended our analysis to simulate the crack propagation path and the failure mode of the standard specimen with multiple cracks under the uniaxial compression.We investigated the impacts of the effects of different K_ⅡC/K_ⅠC,different crack inclinations and different number of initial cracks on the simulation results.（4）Based on the established mixed model Ⅰ-Ⅱ cracks propagation simulation method,a potential tensile collapse of dangerous rock body in an actual project is selected for simulation analysis.Ⅰn this simulation,we consider the presence of a pre-existing crack at the trailing edge of dangerous rock body.Our aim is to ascertain the propagation path of the crack and the deformation model of the dangerous rock body under the influence of its self-weight stress field.更多还原