基于PFC的单节理岩石裂缝演化数值模拟

Numerical simulation of single-joint rock fracture evolution based on PFC

岩石中普遍存在各向异性裂隙,其中单节理作为一种简单基础的裂隙结构,其力学行为研究可为评价和预测更复杂岩石体系的力学性能奠定基础。为研究单节理岩石的微观裂缝演化机制与规律,探究其对宏观力学参数和破坏特征的影响,该文以滇中引水工程大理段香炉山隧洞的节理岩体为研究对象,采用二维颗粒流数值程序对完整岩石和单节理岩石进行单轴压缩模拟试验,分析节理长度及倾角的变化对宏观力学参数和破坏特征的影响。结果表明:单节理岩石的节理越长、倾角越小,单轴抗压强度、峰值应变和弹性模量越小;节理越长,节理倾角对峰值应力、峰值应变和弹性模量的敏感性越高;试样大多呈张拉破坏,裂纹萌生顺序为翼裂纹、剪切裂纹、次生剪切裂纹和远场裂纹;随着节理倾角增大,起裂位置由节理中部向尖端转移,起裂方向由垂直于节理倾向转为平行于节理倾向;节理长度越长,破坏形成的主拉裂纹越少,裂纹类型越简单,翼裂纹起裂越早,剪切裂纹起裂越晚。

[Objective]In the expansive field of geology,where anisotropic fractures intricately pattern rocks,this study focuses on unraveling the nuanced evolution mechanisms of microscopic cracks within rocks featuring a solitary joint.Rooted in the jointed rock mass of the Xianglushan Tunnel in the Dianzhong Diversion Project,China,the research aims to discern the profound impact of single joints on a broad spectrum of macroscopic mechanical parameters and failure characteristics.This exploration seeks to deepen our understanding of the intricate interplay between micro-mechanical phenomena and the broader geological context,contributing valuable insights to the field of rock mechanics.[Methods]In this pioneering study,the methodology hinges on leveraging the advanced two-dimensional particle flow code(PFC2D)to meticulously orchestrate uniaxial compression simulation tests.The experimental scope spans both pristine rock specimens and those featuring a distinct single joint.The crux of the analysis entails a detailed exploration into the repercussions of joint length and inclination on a diverse array of macroscopic mechanical parameters and failure characteristics.To dissect the intricate relationships between joint attributes and the mechanical response of the rock mass,the study employs numerical experiments.These simulations,akin to a virtual laboratory,diligently replicate the dynamic response of the rock mass under varying joint conditions.The computational prowess of PFC2D ensures a high-fidelity representation,unraveling the nuanced interplay between joint characteristics and macroscopic mechanical behaviors.The numerical experiments extend beyond the confines of traditional physical testing,enabling a systematic investigation across a spectrum of joint conditions.This not only enhances the efficiency of the study but also broadens the horizons of exploration,providing insights into diverse joint scenarios that might pose challenges in a laboratory setting.[Results]The results indicated that for rocks with a single joint:(1)smaller joint inclinations and larger lengths corresponded to decreased uniaxial compressive strength,peak strain,and elastic modulus.(2)Longer joints exhibited increased sensitivity of joint inclination to peak stress,peak strain,and elastic modulus.(3)Specimens predominantly underwent tensile failure,with a sequence of crack initiation:wing cracks,shear cracks,secondary shear cracks,and far-field cracks.(4)As the joint inclination increased,the crack initiation location shifted from the middle to the tip of the joint,and the crack initiation direction changed from perpendicular to the joint strike to parallel.(5)Longer joints resulted in fewer primary tensile cracks,simpler crack types,earlier initiation of wing cracks,and delayed initiation of shear cracks.[Conclusions]This groundbreaking research represents a significant leap forward in unraveling the micro-mechanical intricacies inherent in single-joint rocks and their profound implications on macroscopic mechanical parameters and failure characteristics.The acquired insights not only substantively contribute to the academic discourse in the field of geomechanics but also hold practical implications for the assessment and prediction of the mechanical behavior of jointed rock masses in engineering applications.The findings serve as a cornerstone,providing a robust foundation for future research endeavors in the dynamic realm of rock mechanics.The practical implications extend beyond theoretical boundaries,offering valuable guidance for engineers and practitioners engaged in the design and evaluation of structures within jointed rock formations,thereby bridging the gap between theoretical understanding and real-world applications.