Rainfall infiltration threshold for loess slope instability
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Abstract:
With the growth of the infiltrated water amount,the loess matrix suction will decrease,and lead to the reduction of slope shearing strength that lets the slope under an unstable condition and prone to occur landslides or other geotechnical disasters.The variation of the seepage field as one of the important influence factors of slope stability has been widely agreed with the majority of geotechnical scholars.However,most of the simulation analyses were limited to experimental or hypothetical simulation due to the lack of real monitoring data. According to the measurement of loess property in both southern and western slopes,the Geo-Studio software was selected to study and analyze the impact of rainfall seepage on loess slope stability in Baota Mountain.Based on four kinds of geotechnical data ("slow shear","triaxial","effective",and "total stress"),the stability of the western slope of Baota Mountain was analyzed and simulated under different rainfall scenarios. By comprehensively comparing the results simulated by four kinds of loess parameters,the influence of rainfall infiltration on slope stability was relatively lower with "total stress" and "slow shear" parameters.When the rainfall over 100 mm in 24 h,the slope stability decreased abruptly under the condition of "triaxial" and "effective".The "triaxial" test can strictly control the drainage conditions and can obtain the effective shear strength indexes of the soil through the pore water pressure.The base of Baota Mountain is generally stable,and the possibility of having large landslides is relatively lower. However,the potential risk of slope collapse disaster still existed on the Baota Mountain.Under extreme climatic conditions,where the accumulated rainfall exceeded 100 mm in 24 h,the surface loess on the slope will be supersaturated,and then prone to have small/mediumscaled collapse.It is recommended to take relevant measures to manage the risk slope of Baota Mountain from the perspective of how to prevent slope erosion and reduce rainfall infiltration on the slope.In addition,combined with the simulation results,a reservation system based on real-time rainfall monitoring should be established to properly carry out disaster prevention.