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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。
In natural rock mass, different anisotropic structural planes with different lithology are widely developed. The research on the deformation and strength characteristics of heterosexual structural planes aims to provide the basis for the evaluation and utilization of rock mass stability. This paper selects the typical Jurassic sandstone-mudstone heterotrophic strata in the Three Gorges Reservoir Area. Firstly, using the fractal geometry theory, the roughness coefficient JRC values of flat and 4 different irregular undulating structural planes are calculated quantitatively. Then, Particle flow program, the numerical shear tests of the above five kinds of morphological anisotropic structural planes were carried out respectively, and the shear stress-displacement curves of the morphological structural planes under different normal stresses were obtained. According to the results of numerical experiments, the JRC-JCS model of Barton is used to analyze the strength characteristics of the heterosexual structural plane, and the comparison is made with that of the isotropic structural plane. Finally, based on the shear failure mechanism of the heterosexual surface, two concepts of strength factor are introduced and two new types of improved Barton criteria are proposed. The results show that the shear strength of the heterosexual rock mass is between that of two isotropic structural planes with the same roughness, and the strength of the isotropic structural plane is close to that of the soft rock under lower normal stress, High normal stress deviate to hard rock isostructural surface strength, in line with the type Ⅱ improved Barton’s criterion. In practical engineering, the improvement criterion can be used and the stability of the rock mass can be evaluated according to the stress state of the heterostructural surface, which makes up for the deficiencies of previous studies.