UNIAXIAL COMPRESSION EXPERIMENTAL RESEARCH ON DEFORMATION AND FAILURE PROPERTIES OF BRITTLE MARBLE SPECIMEN WITH PRE-EXISTING FISSURES
YANG Shengqi1，DAI Yonghao2，HAN Lijun1，HE Yongnian1，LI Yushou1
(1. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and Technology，Xuzhou，Jiangsu 221008，China；2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China)
Abstract：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).
