基于PFC^(2D)数值试验的异性结构面剪切强度特性研究  

Study of shear strength characteristics of heterogeneous discontinuities using PFC^(2D) simulation

作　　者：张雅慧[1] 汪丁建[1] 唐辉明[1] 李长冬[1] 易贤龙[1] 

机构地区：[1]中国地质大学(武汉)工程学院,湖北武汉430074

出　　处：《岩土力学》2016年第4期1031-1041,共11页Rock and Soil Mechanics

基　　金：国家重点基础研究发展计划(973)项目(No.2011CB710606);国家自然科学基金重点项目(No.41230637)~~

摘　　要：天然岩体中广泛发育两侧岩性不同的异性结构面,开展异性结构面变形和强度特性研究旨在为岩体稳定性评价和利用提供依据。选取三峡库区侏罗系典型的砂岩-泥岩异性岩层,首先运用分形几何理论,定量计算了平直和4种不同不规则起伏形态结构面的粗糙度系数JRC值,然后基于PFC^(2D)颗粒流程序,分别开展了以上5种形态异性结构面的数值剪切试验,获得了各形态结构面在不同正应力下的剪切应力-位移曲线。根据数值试验结果,采用巴顿的JRC-JCS模型分析了异性结构面强度特性,并与同性结构面强度性质进行对比研究。最后,在考虑异性结构面剪切破坏机制的基础上,引入强度因子的概念,提出了新的适用于异性结构面强度评价的两类改进巴顿准则。研究结果表明:异性岩体结构面抗剪强度介于相同粗糙度的两种同性结构面强度之间,在较低正应力下接近软岩同性结构面强度,符合Ⅰ型改进巴顿准则;在较高正应力下偏向硬岩同性结构面强度,符合Ⅱ型改进巴顿准则。实际工程中可利用改进准则并根据异性结构面应力状态对岩体稳定性进行评价,弥补了以往研究的不足。Heterogeneous discontinuities with different properties are widely distributed in rock masses. The unconformity is usually beyond consideration; however the deformation and strength characteristics of heterogeneous discontinuities yield the basis for the stability evaluation of rock mass. In this study, samples from the typical sandstone-mudstone interbeds in the Jurassic in Three Gorges Reservoir Region are tested. The joint roughness coefficient（JRC） values of flat discontinuity and four different irregularly shaped discontinuities are calculated in a quantitative approach using the fractal geometry theory. Then the numerical shear tests on these five kinds of samples are carried out by the PFC^（2D） software. The shear stress-displacement curves are acquired for heterogeneous discontinuities with different roughnesses under various normal stresses. According to numerical results, the strength characteristics of heterogeneous discontinuities are analyzed using Barton＇s JRC-JCS model and compared with the homogeneous discontinuities. At last, on the basis of shear failure mechanisms of heterogeneous discontinuities, two types of modified Barton criteria（i.e., type Ⅰ and type Ⅱ） are proposed by introducing a concept of strength factor, which are applicable to strength evaluation of heterogeneous discontinuities. The results indicate that shear strength of heterogeneous discontinuity falls between those of two homogeneous rock discontinuities with the same joint roughness, and is close to strength of soft rock discontinuity at low normal stress, which follows the modified type I Barton criterion. At high normal stress, the strength of heterogeneous discontinuity is close to that of the homogeneous discontinuities of hard rock, which follows the modified type Ⅱ Barton criterion. In practical project, the evaluation of rock mass stability can employ the modified criteria in combination with the stress state of heterogeneous discontinuities, which improves on some of the shortcomings of previous st

关 键 词：异性结构面 抗剪强度 PFC2D程序 数值试验 JRC-JCS模型 

分 类 号：P642.3[天文地球—工程地质学]