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<p>On December 18, 2023, a 6.2-magnitude earthquake in Jishishan, Gansu Province triggered a large-scale loess liquefaction flow-slip disaster in Zhongchuan Township, resulting in 20 fatalities. It is crucial to investigate the liquefaction characteristics and occurrence mechanism of this disaster to understand the long-distance and low-angle liquefaction instability slip mechanism of loess slopes. Therefore, field investigations were conducted at the Zhongchuan liquefied flow-slip site, and undisturbed samples of saturated loess were collected from the site. Based on indoor dynamic triaxial tests, scanning electron microscopy (SEM), and particle and crack analysis system (PCAS) analysis, this study systematically investigated the cumulative evolution of dynamic pore water pressure and dynamic strain, stress path response, and mesostructural change during liquefaction, and further explored the underlying mechanism of the earthquake liquefaction disaster. The results demonstrated that the dynamic strain and dynamic pore water pressure accumulated with the number of vibrations, transitioning from the initial steady slow growth to rapid and fluctuating growth. During liquefaction, the area of the stress–strain hysteresis loop increased with an increase in the number of vibrations, the slope of its long axis decreased, and the short axis elongated. The effective stress path exhibited a linear variation under different dynamic stresses, and the average effective stress in cyclic shear continued to decrease but rarely reached the state of initial liquefaction. The undisturbed loess was characterized by a point-contact-dominated and weakly cemented overhead macropore structure with clear particle boundaries. After liquefaction, the soil structure was damaged, the number of pores increased, and the shape coefficient distribution indicated that the proportion of irregular and slender pores increased significantly. Under the coupling effect of the seismic load and hydraulic force, the soil skeleton deforms rapidly, and the failure of cementation and the contact system leads to the collapse of the overhead structure, redistribution of particle migration, pore collapse, and pore connectivity. These processes caused a surge in dynamic pore water pressure and a sharp decrease in effective stress, ultimately inducing liquefaction.</p>

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Study on the liquefaction mechanism of the saturated loess in Zhongchuan County induced by the Jishishan MS 6.2 earthquake

  • 期刊论文

  • 发表日期：

    2026年4月20日

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  • Shichao Jia,
  • Qian Wang,
  • Xiumei Zhong,
  • Yi Wang,
  • Xuefeng Hu,
  • Yingshi Wang,
  • Wanxiao Li

摘要

On December 18, 2023, a 6.2-magnitude earthquake in Jishishan, Gansu Province triggered a large-scale loess liquefaction flow-slip disaster in Zhongchuan Township, resulting in 20 fatalities. It is crucial to investigate the liquefaction characteristics and occurrence mechanism of this disaster to understand the long-distance and low-angle liquefaction instability slip mechanism of loess slopes. Therefore, field investigations were conducted at the Zhongchuan liquefied flow-slip site, and undisturbed samples of saturated loess were collected from the site. Based on indoor dynamic triaxial tests, scanning electron microscopy (SEM), and particle and crack analysis system (PCAS) analysis, this study systematically investigated the cumulative evolution of dynamic pore water pressure and dynamic strain, stress path response, and mesostructural change during liquefaction, and further explored the underlying mechanism of the earthquake liquefaction disaster. The results demonstrated that the dynamic strain and dynamic pore water pressure accumulated with the number of vibrations, transitioning from the initial steady slow growth to rapid and fluctuating growth. During liquefaction, the area of the stress–strain hysteresis loop increased with an increase in the number of vibrations, the slope of its long axis decreased, and the short axis elongated. The effective stress path exhibited a linear variation under different dynamic stresses, and the average effective stress in cyclic shear continued to decrease but rarely reached the state of initial liquefaction. The undisturbed loess was characterized by a point-contact-dominated and weakly cemented overhead macropore structure with clear particle boundaries. After liquefaction, the soil structure was damaged, the number of pores increased, and the shape coefficient distribution indicated that the proportion of irregular and slender pores increased significantly. Under the coupling effect of the seismic load and hydraulic force, the soil skeleton deforms rapidly, and the failure of cementation and the contact system leads to the collapse of the overhead structure, redistribution of particle migration, pore collapse, and pore connectivity. These processes caused a surge in dynamic pore water pressure and a sharp decrease in effective stress, ultimately inducing liquefaction.