It is important to couple the analysis of the effects of topography, climate, vegetation, and human activities on soil erosion to understand the dynamic characteristics of soil erosion under environmental change. This study investigated the impacts of geographic unit difference on soil erosion in the Shaanxi Province in China through the model simulation (RUSLE) and quantitative analysis. The following results were achieved. First, the amplitudes of environmental change varied at different rates in the three regions over the past 35 years (1980–2015). The frequency of severe rainstorms, the main trigger for soil erosion, intensified most in the Loess Plateau compared to the Qinling Mountains and Guanzhong Plain and led to an increase in the number of geological disasters in that region. In addition, after the 1990s, vegetation improved most in the Loess Plateau, and socioeconomic activities related to urbanization, another important driver of soil erosion, increased the most in Guanzhong Plain. Second, improved vegetation cover was the most significant contributor to the reduction in soil erosion during the past 35 years, although intensified rainstorms and human activities enhanced the risks of soil erosion. Third, the comparative study revealed that different environmental parameters dominated soil erosion processes in the three regions.
Rainfall usually leads to soil slope sliding and instability, which affects the safety of foundation pit, especially in the case of heavy rainfall. This study took the 7.20 Henan rainstorm as the background, where in the process of construction, after three days of rainstorm of 617.7 mm deep, the horizontal displacement of supporting structures of a foundation pit in Zhengzhou city increased by 6.3 mm. Therefore, it is of great significance to study the mechanism of deformation induced by rainstorm of foundation pits. Five numerical models considering different rainfall factors were developed to simulate the rainstorm process based on the monitoring data. The deformation mechanism and the effect factors of deformation on the foundation pit during rainstorm were analyzed, and some preventive measures were put forward for when the foundation pit engineering faces a heavy rainstorm. Under the action of the rainstorm, the supporting structure and the surface settlement had a signification deformation caused by the heavy rainfall on this typical foundation pit, and the maximum bending moment and maximum displacement of the supporting structure shifted up to different degrees. The main factors affecting the deep foundation pit of the metro by heavy rain are the steel strut falling off and the whole foundation pit filling with water, while the influence caused by the rise in the groundwater level, water standing load, and soil softening is small.
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