Numerical approach to evaluate the influence of water saturation on the strength of Neogene Tuff in Utsunomiya city, Japan

Evaluation of the deformation behavior due to drying is crucial in underground construction works. Especially, geological repository for High-Level Radioactive Waste (HLW) shall be carefully selected to act as a natural barrier to prevent radioactive nuclide leaks. Uniaxial Compressive Strength (UCS) is one such governing factors when designing or selecting a suitable location for such underground storage compartments or access tunnels. Since nuclide leakage through geological repositories, intact rocks UCS will vary with the drying conditions. Hence, it is vital to evaluate the behavior of UCS subject to the conditions prescribed. A variety of statistical models has been built to govern the interdependency between UCS and water content. However, there are no significant amount of research have been conducted to emphasize the UCS variation with the degree of saturation under the influence of drying condition. Numerically, Richard’s equation exact solution in Neuman boundary condition has been derived to exploit the degree of saturation with respect to time and position. Experimentally, obtain the UCS variation with the degree of saturation pertaining to the Neogene Tuff in Utsunomiya city, Japan. A best fit statistical model was generated for experimental data between UCS variation and the degree of saturation. Then, the experimental saturation degree was replaced by Richard’s equation exact solution saturation degree values. Surprisingly, produced graphs for experimental data and numerical analysis data for exact solution were perfectly overlapped. Results point out that change of UCS shows similar characteristics, which exponentially decrease, with both experimental saturation values and exact solution saturation values influenced the drying condition. Moreover, it suggests that UCS value can be predicted subject to the time and position in the sedimentary rocks under drying conditions.