Presentation Information
[3K0101-07-03]Research on the Loading-rate Dependency of Rock under Shear Conditions
○Jingai Wang1[Student presentation: Master’s course], Kimihiro Hashiba1, Katsunori Fukui1 (1. The University of Tokyo)
Chairperson: 濵中 晃弘（九州大学）
Keywords:
Direct shear test,Shear strength,Loading-rate dependency,Time-dependent behavior
Rock engineering structures such as tunnels, underground caverns, and slopes are subjected to complex stress states involving compression, tension, and shear throughout their service life. While compression and tension tests provide fundamental information on rock strength, they are insufficient to fully describe deformation and failure under realistic stress conditions, making shear testing indispensable. Rock strength is influenced by multiple factors, including stress state, specimen geometry, water content, and loading rate. Although these influences have been extensively studied for compressive and tensile behavior, their effects on the shear response of rocks, particularly with respect to loading-rate dependency and shear geometry, remain poorly understood. In this study, the loading-rate dependency of shear strength of Kimachi sandstone was investigated through a series of laboratory shear tests. All experiments were performed under dry conditions at room temperature. Cylindrical specimens with a diameter and height of 25 mm were tested using a newly designed shear fixture developed for a uniaxial loading machine. Shear tests were carried out at four shear angles to examine the influence of shear geometry on rate-dependent behavior. Two types of shear tests were conducted: constant loading-rate shear tests at three displacement rates, and loading-rate switching shear tests in which two loading rates were alternated at a constant displacement interval within a single test. The loading-rate dependency of shear strength was evaluated using a power-law relationship between shear strength and loading rate. The results show that shear strength generally increases with loading rate and that a useful quantitative index for characterizing the time-dependent shear behavior of the sandstone was obtained. These findings contribute to a systematic understanding of loading-rate effects on shear failure and provide a basis for evaluating time-dependent rock behavior in engineering applications.