柱状节理岩体各向异性特性及尺寸效应研究

 白鹤滩水电站坝基基岩及深部洞室围岩以柱状节理岩体为主，其力学特性极其复杂。为此，开发多弱面软化本构模型，可以方便地定义和描述多组斜交节理面的力学属性和屈服后的软化特性；并考虑柱状节理岩体内部介质的非均匀性，从细观角度建立整体力学属性满足Weibull分布的概率模型；在对概率分布参数进行敏感性分析的基础上，结合刚性承压板试验结果，确定反映现场岩体结构的概率分布参数。同时，采用Voronoi算法构建了无规则性和随机性排列的四面体、五面体和六面体柱面的随机模型，综合该三方面因素对柱状节理岩体的各向异性特性展开研究，得出不同方向承载性能和变形特性的差异。对不同尺寸下多组试块进行分析计算，获取了不同方向的弹性模量和抗压强度随试块尺寸的变化曲线，证明柱状节理岩体还具有明显的尺寸效应，并确定了其特征尺度。

RESEARCH ON ANISOTROPIC CHARACTERISTICS AND SIZE EFFECT OF COLUMNAR JOINTED ROCK MASS

The mechanical properties of columnar jointed rock mass，which is the main composition of dam foundation and surrounding rock of deep cavern at Baihetan hydropower station，are very complex. In order to study the anisotropic characteristics of columnar jointed rock mass，three factors are considered. First，a mixed multi-weakness planes softening constitutive model is built. It can be used to define and describe the mechanical properties and the softening characteristics of multiple oblique joint planes after failure. Second，considering the heterogeneity of the columnar jointed rock mass，a probability model is established through assigning mechanical parameters throughout the numerical specimens by following Weibull distribution. On the basis of sensitivity analysis of probability distribution parameters，combining with the experimental results of rigid bearing plate，the reasonable distribution parameters that fit the structure of field rock mass are computed. Third，column section of jointed rock mass is composed by tetrahedron，pentahedron and hexahedron randomly and irregularly. Voronoi algorithm is used to achieve the randomness of geometric shape and irregularity of arraying order. Taking all these factors into account，the bearing capacity and deformation characteristics in different directions are obtained. The results turn out to be obviously distinct in different directions. At the same time，multiple test blocks with different sizes are analyzed；and the curves of equivalent elastic modulus and unconfined compressive strength in different directions changing with size are acquired. It is shown that the columnar jointed rock mass has obvious size effect；meanwhile the characteristic scale is determined.