RESEARCH ON ANISOTROPIC CHARACTERISTICS AND SIZE EFFECT OF COLUMNAR JOINTED ROCK MASS
ZHU Daojian1，2，YANG Linde1，2，CAI Yongchang1，2
(1. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China；2. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education，Tongji University，Shanghai 200092，China)
Abstract：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.
