Abstract
Pore-water pressure generation in the saturated carbonate fault zone plays a key role in the initiation of the Daguangbao landslide, which is the largest landslide triggered by the 2008 Wenchuan earthquake in China. This paper examines the pore-water pressure behavior and the influence of cyclic stress and initial stress state, and establishes a pore-water pressure model of carbonate fault materials. A series of cyclic triaxial tests of saturated carbonate fault materials were carried out, covering a broad range of frequencies, cyclic shear stress ratios and confining pressures. The test results show that the pore-water pressure in the materials increases rapidly under cyclic loading, revealing a significant liquefaction potential. The generation of pore-water pressure is barely affected by frequency. The higher cyclic shear stress ratio accelerates the generation of the pore-water pressure, while the higher confining pressure increases liquefaction resistance. Furthermore, an energy method is proposed to evaluate the development behavior of the pore-water pressure. An energy-based pore-water pressure model that accounts for the effects of frequency, cyclic shear stress ratio and confining pressure is established. The generation of the pore-water pressure is attributed to the grain crushing in the special fault materials with low-strength calcareous cementation. This work provides a novel model and some innovative observations for better understanding the pore-water pressure behavior of carbonate fault materials under seismic loading.
Highlights
IntroductionDuring the long-term tectonic activities, the bedding fault was formed and developed (Wang, 2009)
The generation of pore-water pressure under seismic loading resulted in the strength degradation in the sliding zone, which was the key factor for the initiation and movement of landslide
Frequency and cyclic shear stress ratio have little effect on the total dissipated energy required to trigger liquefaction, while the confining pressure has a significant effect
Summary
During the long-term tectonic activities, the bedding fault was formed and developed (Wang, 2009). The strength of bedding fault materials is very low. It has been previously reported that some large landslides initiated along the bedding fault, such as the Carbonate Fault Materials Tests. The generation of pore-water pressure under seismic loading resulted in the strength degradation in the sliding zone, which was the key factor for the initiation and movement of landslide. Wang et al (2014) proposed that liquefaction of the runout path material enhanced the mobility of the Donghekou landslide through the ring shear test. Pei et al (2017) reported that the steady-state strength of the sliding zone was close to 0 due to the generation of pore-water pressure, which was the reason for the long-distance and fluidized movement of the Shibeiyuan landslide
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