Laboratory creep tests for time-dependent properties of a marble in Jinping II hydropower station
Xiaojun Zhao1, Bingrui Chen2*, Hongbo Zhao1, Binghui Jie3, Zhengfang Ning4
1 School of Civil Engineering, Henan Polytechnic University, Jiaozuo, 454003, China
2 State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan, 430071, China
3 Ertan Hydropower Development Co., Ltd., Chengdu, 610051, China
4 School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China
Abstract: 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 c0nstant; under c0nstantly 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 conditi0ns. 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.
Key words: time-dependent mechanical behaviors; marble; long-term strength; the Poisson’s ratio of rocks;
rock creep
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