考虑三维岩体结构面各向异性特征的剪切强度研究

The presence of discontinuities is inherent to almost any rock mass and is a major contributor to strength and deformation of rock structures. To date, many criterion have been proposed to estimate peak shear strength of rock discontinuities. Although these criteria have improved our understanding of the shear behavior of rock joints, there are still some limitations that should be recognized. Especially, the criterion cannot describe anisotropic properties of rock discontinuities. To comprehensively predict peak shear strength of rock discontinuities, it is a key issue how to accurately quantify characteristics of rock discontinuities and how to accurately estimate the relationship between the surface’s characteristics and the shear behavior. First，On the basis of the structural properties and randomness characteristic of spatial distribution about rock mass, the variogram of geological statistics is used to analyze the anisotropic character of rock discontinuities and a new method is proposed to describe anisotropic characteristics of rock discontinuities roughness which is expressed by the sill and the range of variogram. Second，we obtain the data described discontinuities topography by 3-D laser scanner, and on the basis, calculate the parameters both the sill and the range along different direction on the discontinuities and analyze the anisotropic characteristics used the proposed method. Therefore, we can verify the feasibility of this method. And then, we develop anisotropy and size effects of shear strength test based on 3-D printing technology. Furthermore, we can test the validity and reliability of the method. Third, we develop a new shear strength criteria based on anisotropic properties of rock discontinuities and data of shear strength experiment. The results will be useful for comprehensively understanding the shear behavior and provide a helpful way to estimate the shear strength of rock discontinuities.

结构面抗剪强度是影响岩体稳定性的重要因素。因此，岩体结构面峰值剪切强度一直是岩石力学界研究的热点。由于结构面形貌的复杂性，特别是各向异性特征的存在，现有剪切力学模型不能反映其抗剪强度的全部力学特性。模型能否准确进行预测，关键是结构面形貌特征如何定量化表征及如何准确评估形貌参数与其力学行为的关系。基于岩体参数具有空间变异性的考虑，本课题将变异函数法应用到岩体结构面粗糙度各向异性的分析中，提出用变异函数参数（变程和基台）表征结构面粗糙度各向异性的新方法。然后，采用三维激光扫描仪获取岩体结构面三维形貌数据，计算其各方向的变异函数参数，应用所提方法分析其各向异性特征。同时，采用3D打印技术开展类岩体结构面各向异性及尺寸效应的剪切力学试验。最后，通过试验数据分析，结合结构面粗糙度各向异性表征方法，建立考虑岩体结构面各向异性特征的峰值剪切强度模型。研究结果为科学预测岩体结构面抗剪强度提供一种新方法。

结构面对岩体力学性质有重要的影响，在某种程度上直接控制岩体工程的稳定性。该项目针对岩体结构面粗糙度对其剪切力学特性的影响，开展了考虑各向异性特征的岩体结构面粗糙度的定量化表征；进行了岩体结构面各向异性及尺寸效应剪切力学试验，建立了考虑各向异性特征三维岩体结构面剪切强度模型。. 具体研究工作如下：①采用地质统计学中变异函数分析方法提出了描述结构面粗糙度各向异性特征的SRv（Surface Roughness by variation function）法，于此同时结合数字图像处理技术开发了相关计算程序，实例分析证明，该方法能够较好地定量表征结构面粗糙度各向异性特征；②基于投影覆盖法计算结构面分形维数时三角形单元划分的缺陷，从概率分析角度考虑，改进了估算结构面分维数的投影覆盖法，并开发了相关计算程序，实例分析证明，基于随机数进行三角形单元划分更符合实际结构面形貌特征，从而估算结构面分维数更精准；③分别采用SRv法和改进投影覆盖法研究了不同类型结构面粗糙度的尺寸效应特征，结果表明，结构面类型不同，尺寸效应特征有所区别，总的来讲包含正尺寸效应特征、负尺寸效应特征、无尺寸效应特征；④采用描述结构面粗糙度各向异性特征SRv法，结合Barton 强度公式，提出了考虑各向异性特征的岩体结构面峰值剪切强度模型，试验表明，该模型能够较好地预测结构面峰值剪切强度；⑤基于岩石试件力学试验具有不可重复性缺陷，应用三维扫描技术和3D打印技术开展了类岩石结构面各向异性和尺寸效应的剪切力学试验，该研究方法是岩体结构面各向异性、尺寸效应剪切力学试验新探索，为全面认识结构面剪切力学性质提供一种新方法。. 该项目开展取得的成果将为岩体结构面剪切力学性质的精准把握提供一种新的评估方法；另外结构面粗糙度的定量化描述也将为深入研究复杂应力场作用下节理岩体渗流机理奠定一定的基础。