In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station,uniaxial creep tests were carried out by using the triaxial testing machine RC-2000.The axial compressive load was applied step by step and each creep stage was kept for over several days.Test results show that:(1) The lateral deformation of rock specimens is 2-3 times the axial compressive deformation and accelerates drastically before damage,which may be employed as an indicator to predict the excavation-induced instability of rocks.(2) The resultant deformation changes from compression to expansion when the Poisson's ratio is larger than 0.5,indicating the starting point of damage.(3) In the step-loading stages,the Poisson's ratio approximately remains constant;under constantly imposed load,the Poisson's ratio changes with elapsed time,growing continuously before the specimen is damaged.(4) When the applied load reaches a certain threshold value,the rock deteriorates with time,and the strength of rocks approximately has a negative exponent relation with time.(5) The failure modes of the deep marble are different in long-and short-term loading conditions.Under the condition of short-term loading,the specimen presents a mode of tensile failure;while under the condition of long-term loading,the specimen presents a mode of shear failure,followed by tensile failure.
Xiaojun ZhaoBingrui ChenHongbo ZhaoBinghui JieZhengfang Ning
