How Heavy Rain and Slope Angle Affect Slope Stability and Failure

Jim Crocker
1st March, 2025

How Heavy Rain and Slope Angle Affect Slope Stability and Failure
Image Source: © Natural Science News. This image is an artistic rendition.

Key Findings

  • In China’s Three Gorges area, heavy rains and steeper hills greatly raise landslide risks
  • More rain washes away fine soil, weakening slopes and making them unstable
  • Researchers created formulas to better predict and prevent future landslides
Slope stability is a critical concern in regions prone to heavy rainfall and earthquakes, such as the areas affected by the 2008 Mw7.9 Wenchuan earthquake in China. Landslides triggered by such events can cause significant environmental and infrastructural damage. Understanding the factors that influence slope stability is essential for effective disaster prevention and land management. A recent study conducted by researchers at Chongqing Three Gorges University and Guizhou University[1] delves into the impact of rainfall intensity and slope inclination on the stability of soil-rock mixture slopes. While previous research has primarily focused on the role of rock content in slope failure, this study explores the combined effects of varying rainfall intensities and slope angles, providing a more comprehensive understanding of the conditions that lead to slope instability. The research builds on earlier findings, such as those from the Wenchuan earthquake, where the proportion of gravel in landslide deposits was shown to influence runoff and sediment yield[2]. Additionally, studies on loess spoil slopes under rainfall conditions highlighted different failure modes and the importance of soil composition in slope stability[3]. By integrating these insights, the current study offers a deeper analysis of how mixed soil-rock compositions respond to environmental stressors. To investigate these dynamics, the research team conducted model tests on soil-rock mixture slopes under controlled conditions. They varied both the intensity of artificial rainfall and the inclination of the slopes to observe changes in water content, earth pressure, pore water pressure, and eventual failure modes. The experiments revealed that higher rainfall intensities and steeper slopes significantly increase the likelihood of slope instability. Specifically, increased rainfall leads to higher water content within the soil-rock mixture, elevating earth and pore water pressures. These factors collectively weaken the slope structure, making it more susceptible to failure. One of the key findings is the progressive loss of fine particles from the slope as rainfall intensity and slope inclination increase. This loss undermines the soil's cohesion, further destabilizing the slope. The study quantified these effects by establishing calculation formulas that relate fine particle content, maximum water content, maximum earth pressure, and maximum pore water pressure to the influencing factors of rainfall intensity and slope inclination. These formulas provide a valuable tool for predicting slope behavior under various environmental conditions. The research also identified specific failure modes induced by rainfall. In line with previous studies[2][3], the failure process occurs in distinct stages. Initially, water infiltration increases the slope's water content, followed by a rise in earth and pore water pressures. Eventually, the slope succumbs to failure, often resulting in landslides that can vary in size and depth depending on the slope's composition and the intensity of the rainfall. By incorporating these findings, the study enhances existing erosion and landslide models, offering more accurate predictions and better-informed strategies for landslide prevention and soil conservation. The role of gravel, as highlighted in prior research[2], is further elucidated in the context of soil-rock mixtures, demonstrating how different proportions can influence the overall stability of slopes. The practical implications of this research are significant for regions like the Wenchuan earthquake zone, where landslides pose ongoing risks. The established relationships and predictive formulas can aid in designing more resilient slope structures and implementing effective water and soil conservation measures. Additionally, understanding the interplay between rainfall intensity and slope inclination allows for better risk assessment and disaster preparedness planning. In summary, the study by Chongqing Three Gorges University and Guizhou University advances our understanding of slope stability by examining the combined effects of rainfall intensity and slope inclination on soil-rock mixtures. By building on previous research and introducing new methodological approaches, the study provides valuable insights and tools for mitigating landslide risks and enhancing environmental resilience in earthquake-prone areas.

Environment

References

Main Study

1) Investigating the coupling effects of rainfall intensity and slope inclination on soil-rock mixture slope stability and failure modes

Published 28th February, 2025

https://doi.org/10.1371/journal.pone.0314752

Related Studies

2) Water and soil loss from landslide deposits as a function of gravel content in the Wenchuan earthquake area, China, revealed by artificial rainfall simulations.

https://doi.org/10.1371/journal.pone.0196657

3) Experimental study on the failure process and modes of loess spoil slope induced by rainfall and engineering disturbance.

https://doi.org/10.1371/journal.pone.0305871


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