基于Oda裂隙结构张量的流纹岩各向异性试验研究

岩石内天然存在长度、倾角和形态不同的裂隙,造成岩石的各向异性特征。为揭示岩石内天然随机裂隙发育特征对岩石物理力学特性的影响规律,以泥巴山隧址区采集裂隙性流纹岩为研究对象,首先对试样裂隙进行素描统计分析;然后基于Oda裂隙结构张量,获得天然随机分布裂隙的几何统计参数;最后对裂隙性流纹岩试样分别进行单轴和常规三轴压缩试验,得到不同应力路径下流纹岩的应力-应变曲线及物理力学参数。分析Oda裂隙结构张量定义的各向异性参数与试验获得的力学参数之间的规律,研究结果表明:(1)Oda裂隙结构张量适用于天然随机分布裂隙的几何统计分析,各向异性参数A(F)越大,裂隙优势方向越明显;(2)单轴压缩下,随着各向异性参数I1和A(F)的增大,流纹岩各向异性程度增大,弹性模量减小,泊松比增大;(3)常规三轴压缩下,流纹岩弹性模量和泊松比随各向异性参数改变的规律较不明显,Oda裂隙结构张量不再适用。

Experimental Study of Rhyolite Anisotropy based on Oda Crack Fabric Tensor

A number of cracks with different length, dip angle and pattern exit naturally in rocks, which cause rock's anisotropy. In order to reveal the influence of random crack feature in natural rock on its physical and mechanical properties, taking the rhyolite sampled from Niba Mountain tunnel worksite as object of study, sketching of crack and statistical analysis were conducted first. Then, the geometric statistical parameters of random distributed cracks were obtaine based on Oda crack fabric tensor. Finally, a series of uniaxial compression tests and conventional triaxial compression tests for cracked rhyolite sample were carried out respectively, to obtain its stress-strain curve and mechanical parameters through different stress paths. The anisotropy parameters defined from Oda crack fabric tensor and the experimentally obtained mechanical parameters were analyzed. Results show that (1) Oda crack fabric tensor is applicable to the geometric statistical analysis of random distributed cracks, and the larger the A^(F) is,the more obvious the advantage of crack direction; (2) under uniaxial compression, with the increasing of anisotropy parameters I<\i>₁ and A^(F), the anisotropic degree of rhyolite becomes greater, its elasticity modulus decreases and Poisson's ratio increases; (3) under conventional triaxial compression, the variation of rhyolite elasticity modulus and Poisson's ratio with the variation of anisoptropy parameters becomes unconspicuous,which means that Oda crack fabric tensor is not suitable for above analysis.