断续预制裂隙脆性大理岩变形破坏特性单轴压缩试验研究

 采用岩石力学伺服试验机，对断续预制裂隙脆性大理岩进行单轴压缩试验，基于全程变形曲线的试验结果，分析裂隙参数(岩桥倾角、裂隙间距、裂隙长度、裂隙数目与裂隙倾角)几何分布对大理岩变形破坏特征的影响规律。研究结果表明，与完整大理岩相比，断续预制裂隙大理岩变形呈现出局部化渐近破坏特征，其峰值强度、弹性模量及峰值轴向应变均明显降低，且降低幅度与预制裂隙参数分布形式密切相关；但变形模量除裂隙间距48 mm(降幅24.8%)、含119°岩桥倾角(降幅23.7%)以及含60°裂隙倾角(降幅43.8%)的岩样以外，其他含2条预制裂隙岩样的变形模量降幅均为－3.8%～7.8%，差异较小。裂隙长度越长、裂隙数目越多及裂隙倾角越大，其峰值强度、弹性模量及峰值轴向应变也越低；而岩桥倾角和裂隙间距与力学参数之间规律性不明显。岩样宏观贯通模式主要呈现出拉贯通、压贯通、剪贯通和混合贯通4种，且与预制裂隙的几何分布密切相关。完整岩样呈典型的轴向劈裂拉贯通模式。含较短裂隙长度(16 mm)及较小裂隙倾角(30°)的岩样呈现出拉贯通模式；而含较长裂隙长度(24 mm)和较大裂隙倾角(60°)的岩样呈现出拉剪混合贯通模式。裂隙间距越小以及裂隙数目越多，岩样的贯通模式趋于复杂，呈现出拉剪压混合贯通模式。

UNIAXIAL COMPRESSION EXPERIMENTAL RESEARCH ON DEFORMATION AND FAILURE PROPERTIES OF BRITTLE MARBLE SPECIMEN WITH PRE-EXISTING FISSURES

Uniaxial compression experiments were carried out for brittle marble with pre-existing fissures by the rock mechanics servo-controlled testing system. Based on the experimental results of complete deformation curves,the effect of the geometric distribution of fissure parameters(bridge angle,fissure distance,fissure length,fissure number and fissure angle) on the deformation and failure properties of brittle marble were analyzed. Compared with the intact marble,the marble with pre-existing fissure takes on the localization deformation and asymptotic failure. The peak strength,elastic modulus and peak axial strain of marble with pre-existing fissure are all lower than that of intact marble,and the reduction extent is closely related to the distribution forms of pre-existing fissure. Expect for the marble sample with fissure distance equals 48 mm(the reduction amplitude of deformation modulus is 24.8%),the marble specimen with bridge angle equals 120°(23.7%) and the marble sample with fissure angle equals 60°(43.8%),the reduction amplitude of deformation modulus is in the range of -3.8% to 7.8% for other marble samples with two pre-existing fissures,in which the difference is smaller. The longer the fissure length is,the more the fissure number is and the larger the fissure angle is;the lower the peak strength,the elastic modulus and peak axial strain are;however there are no distinct laws between the bridge angle,fissure distance and mechanical parameters of marble sample. The failure mode of marble specimen takes mainly on the four modes:tensile mode,compression mode,shear mode and mixed mode,which are closely related to the geometric distributions of pre-existing fissure. The intact marble sample takes on the typically axial splitting tensile mode. The rock samples with the shorter fissure length(16 mm) and the smaller fissure angle(30°) take on the tensile mode,however the rock samples with the longer fissure length(24 mm) and the larger fissure angle(60°) take on mixed mode(shear and tensile). The smaller the fissure distance is,and the more the fissure number is,the more complexed the coalescence mode of rock samples is,which takes on mixed mode(shear,tensile and compression).