The Research of Shear Creep Behaviors of Saturated Sericite-Quartz Phyllite

Along with the thorough development of underground engineering, people pay more attention on the long-term deformation stability of the tunnels. However, creep characteristic is an important factor to arouse surrounding rock deformation failures and control engineering designs. Phyllite is a common soft rock in engineering practice, when sample is saturated, water will not only impose the softening effect on phyllite, but also it will influence their creep mechanical properties under the long-term loads. In this paper, selecting samples from headrace tunnel GaoPingpu hydropower station in China, we carried out the shear creep test of saturated phyllite along the schistosity surface under different stress levels. Further, we systematically analyzed and compared the test results with the samples in air-dried conditions, and found that water has great effects on the strength of phyllite: the long-term strength and yield stress of saturated phyllite are only 70-78 and 75-89 % of the air-dried ones respectively. At the same time, based on the Burgers creep model, we discussed the impacts of water on the creep parameters' values of phyllite. This result can provide a theoretical basis to calculate the creep deformation of the tunnel surrounding rocks.