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[SSS07-P08] Rapid transition of friction-wear properties of siliceous sandstone with increasing work rate
The friction-wear properties associated with a fault are important factors to control fault strength and wear accumulation rate, respectively. The evaluation of those properties helps understand the earthquake nucleation mechanisms and improves the estimation of seismic histories inferred from the structure of fault zone. Although the friction-wear properties of various rock types have been experimentally investigated, those of siliceous sandstone remain to be fully clarified. Hirose et al. (2012, JSG) showed a relationship between the decrease in wear rate and the formation of a shiny slickenside on the fault surface (hereinafter, “fault mirror”) inferred from their experiments using carbonate sandstone. Maeda et al. (2021SSJ) then revealed that the friction-wear properties and the conditions for fault mirror generation and destruction of the Indian sandstone (siliceous sandstone), which dominantly comprising quartz (68%), are different from those of carbonate sandstone. They also indicated that the friction-wear properties are classified into four phases based on the state of the sliding fault surface observed after the experiments. In this study, we focus our analysis on the transition associated with two of the four phases from a state with the fault surface completely covered with a fault mirror (Phase 1) to the next state where the mirror surface starts to be partially broken (Phase 2).
We conducted the experiments using a rotary-shear friction apparatus installed in National Research Institute for Earth Science and Disaster Resilience. We recorded normal stress, shear stress, slip velocity, slip displacement, temperature data, and weight of wear products collected after the experiments. We conducted friction-wear experiments at the slip displacement up to ~200 m under the constant normal stress of 0.5 or 1.0 MPa. We calculated friction coefficient and work rate (the product of the shear stress and the slip velocity) based on averages of those values with the displacement between 60 and 100 m as a representative value. We also calculated the integral of the shear stress with respect to the displacement, referred to as the frictional work. The wear rate was also estimated based on the weight of wear products relative to the frictional work. We monitored temperature at the outer rim of the sliding surface using a radiation thermometer (Keyence, IT2-02, IT2-50).
We found that there is a clear difference in friction-wear properties between Phase 1 and Phase 2. For the case with Phase 1, the friction coefficient tends to decrease from 0.6 to 0.2 with increasing work rate from 10-4 to 10-2 (MJ/m2s). The maximum temperature near the sliding surface is less than 100℃, and the wear products are almost negligible in this range of work rate. On the contrary, for the case with Phase 2, the friction coefficient tends to increase with increasing work rate (>10-2 MJ/m2s). The maximum temperature near the sliding surface exceeds 100℃, and the wear rate rapidly increases with the work rate.
Boneh et al. (2013, EPSL) showed that the tribological styles on the simulated fault using carbonate rocks evolves from a brittle two-body mode to a ductile three-body mode where the wear production decreases due to the lubrication caused by the gauge powder covering the fault surface with the increase in slip velocity. In contrast, our results show that the siliceous sandstone has the opposite trend during the transition from Phase 1 to Phase 2, where the wear production increases with the slip velocity. Therefore, it is necessary to construct a wear model that differs from Boneh et al. (2013, EPSL) for siliceous stone.
We conducted the experiments using a rotary-shear friction apparatus installed in National Research Institute for Earth Science and Disaster Resilience. We recorded normal stress, shear stress, slip velocity, slip displacement, temperature data, and weight of wear products collected after the experiments. We conducted friction-wear experiments at the slip displacement up to ~200 m under the constant normal stress of 0.5 or 1.0 MPa. We calculated friction coefficient and work rate (the product of the shear stress and the slip velocity) based on averages of those values with the displacement between 60 and 100 m as a representative value. We also calculated the integral of the shear stress with respect to the displacement, referred to as the frictional work. The wear rate was also estimated based on the weight of wear products relative to the frictional work. We monitored temperature at the outer rim of the sliding surface using a radiation thermometer (Keyence, IT2-02, IT2-50).
We found that there is a clear difference in friction-wear properties between Phase 1 and Phase 2. For the case with Phase 1, the friction coefficient tends to decrease from 0.6 to 0.2 with increasing work rate from 10-4 to 10-2 (MJ/m2s). The maximum temperature near the sliding surface is less than 100℃, and the wear products are almost negligible in this range of work rate. On the contrary, for the case with Phase 2, the friction coefficient tends to increase with increasing work rate (>10-2 MJ/m2s). The maximum temperature near the sliding surface exceeds 100℃, and the wear rate rapidly increases with the work rate.
Boneh et al. (2013, EPSL) showed that the tribological styles on the simulated fault using carbonate rocks evolves from a brittle two-body mode to a ductile three-body mode where the wear production decreases due to the lubrication caused by the gauge powder covering the fault surface with the increase in slip velocity. In contrast, our results show that the siliceous sandstone has the opposite trend during the transition from Phase 1 to Phase 2, where the wear production increases with the slip velocity. Therefore, it is necessary to construct a wear model that differs from Boneh et al. (2013, EPSL) for siliceous stone.