Browsing by Author "Sainoki, A"

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item: Conference-Full-text
Effect of fracture stiffness in a fault damage zone on seismic source parameters of induced fault-slip
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Gang, M; Sainoki, A; Kodama, J; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
It is well recognized that inherent stress concentration within a fault damage zone may lead to induced fault-slip, resulting in severe damage to underground facilities. Previous research suggests that the intensity of fault-slip is influenced not only by the mechanical properties of the fault core but also by the stiffness of the surrounding rock mass, implying that fracture stiffness could be an important factor that needs to be studied. Therefore, in this study, the effect of the fracture stiffness on seismic source parameters of induced fault-slip is investigated using a mine-wide scale heterogeneous continuum model. The model is constructed based on a discrete fracture network within a fault damage zone, utilizing the crack tensor theory and boundary traction method. The fault core is simulated as a discontinuous plane with interface elements at the center of the model, and fault-slip is induced by gradually reducing the effective normal stress on the fault plane. Seismic source parameters are computed and analyzed under various fracture stiffness conditions. Seismically radiated energy is defined as the work done by the stress perturbation across a closed surface at a distance from the earthquake source, while seismic moment is calculated using the moment tensor of a seismic source in an anisotropic medium. This study investigates increasing fracture stiffness while maintaining a normal-to-shear stiffness ratio of three. Dynamic analysis results reveal a notable impact of fracture stiffness on seismically radiated energy and seismic moment, both of which decrease significantly with increasing fracture stiffness. These findings imply the importance of considering fracture stiffness for more accurate estimation of seismically radiated energy and seismic moment.
item: Conference-Full-text
Fundamental study of the influences of discontinuities on rock slope displacement due to excavation
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Kubo, T; Zhang, C; Sainoki, A; Kodama, J; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
In the Higashikagoe limestone quarry, discontinuities are thought to be one of the factors contributing to the deformation of the rock slope. In this study, we investigated the impact of discontinuities and dip angles on slope deformation through numerical simulations, developing four models: a model without any discontinuity and three models with discontinuities of different dip angles. Results showed that discontinuities significantly influence deformation, with forward movement observed in models with discontinuities, aligning with field measurements. This suggests that discontinuities are critical to the deformation of the rock slope in the Higashishikagoe quarry.
item: Conference-Full-text
Numerical analysis of effects of clay on a cut rock slope deformation at an open-pit limestone mine, Japan
(Department of Earth Resources Engineering, University of Moratuwa, 2021-12) Amagu, AC; Zhang, C; Kodama, J; Iwasaki, H; Ikegami, S; Sainoki, A; Fukuda, D; Fujii, Y; Dissanayake, DMDOK; Jayawardena, CL
Rock slope instability is one of the major challenges of rock engineering projects, including open-pit mining. In this regard, rock slope deformation due to excavation, change in temperature, and influence of rainfall and snowfall have been previously investigated to understand characteristics and causes of slope deformation observed at an open-pit limestone quarry in Japan. The results only revealed characteristics of the deformation as forward and downward displacement of the cut rock slope, but its causes were not clarified. To deduce the causes of the rock slope deformation, we employed the 2-dimensional finite element method (2-D FEM) to investigate the deterioration effect of clay found at the footwall of the rock slope in terms of reduction in Young's modulus of the clay based on experimental results. Firstly, change in distances was analysed from displacement data measured by the automated polar system (APS) over five years, which decreases gradually with time. Secondly, the simulation results were discussed and then compared with the measured displacement data, which shows similar tendencies at the middle and top of the rock slope revealing maximum displacement at the middle of the rock slope. Conclusively, deterioration of clay at the footwall of the rock slope is one of the possible causes of the deformation in the quarry.