The Promotion Mechanism of Frozen Stagnant Water on the Sliding in the Loess Landslide Zone of Heifangtai

Mingli Zhang,Zhixiong Zhou,Dekai Wang,Weilin Ye,Zhao Ma,Guang Li,Kai Xia,Huie Chen

doi:10.1155/2021/9749011

Mingli Zhang, Zhixiong Zhou + Show 6 more

Open Access

https://doi.org/10.1155/2021/9749011

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Abstract

Freeze-thaw cycles can significantly change the hydrologic and thermal state of slopes in cold regions and affect their stability. Landslides occur continuously in the slip area of seasonally frozen soil area during the freezing period. The freeze-thaw action and the difference in the characteristics of the underlying surface of the slope are important factors inducing landslides. Taking Heifangtai slope in Gansu Province as an example, the freezing-thawing characteristics of the slope surfaces under different underlying surface conditions were analyzed by field monitoring. A thermohydromechanical coupling model was established to reconstruct the frozen stagnant water process of the Heifangtai landslide zone, and the impact of freeze-thaw action on the loess landslide zone was studied. The results show that differences in the underlying surface led to different freezing-thawing characteristics between the unsaturated area and the groundwater overflow zone. During the freezing period, the soil freezing depth was greater, and the freezing duration was longer in the unsaturated area. The frozen stagnant water effect of the Heifangtai loess landslide zone is obvious. The maximum difference in the groundwater level between February and August could reach nearly 1 m. Meanwhile, the frozen stagnant water process of the Heifangtai landslide zone has a slip-promoting action on the slope. The factor of safety declined during the freezing period and increased during the thawing period. It reached a minimum of 1.42 in February.

Highlights

Loess is distributed in 12 provinces in China, accounting for approximately 6.6% of the total land area of China [1]
If the soil of the groundwater overflow zone freezes during the freezing period, the groundwater level will continue to rise in the slope, increasing the dynamic and static water pressure, which is extremely unfavorable to the stability of the slope
Compared with the soil in the groundwater overflow zone, the soil in the unsaturated area reaches lower temperatures during the freezing period, higher temperatures during the thawing period, thicker freezing depths, and a longer freezing duration. This is because the water content of the soil in the groundwater overflow zone is close to saturation, which is much higher than that of the soil in the unsaturated area of the slope

Summary

Introduction

Loess is distributed in 12 provinces in China, accounting for approximately 6.6% of the total land area of China [1]. Owing to the special structure and water sensitivity of loess, the ecological environment of the Loess Plateau is fragile, and soil erosion is serious, resulting in frequent occurrence of geological disasters, especially landslides. The number of landslides that occur on the Loess Plateau accounts for approximately 1/3 of the total number of landslides every year [4]. A large number of loess landslides result in the destruction of arable land and the inundation of villages. With the advancement of the Belt and Road policy, the increase of engineering activities will further induce loess geological disasters. Landslides have become a major risk of human life and property safety in loess areas

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