Stability Analysis Of Rainfall-induced Shallow Landslide

The stability evaluation of rainfall-induced landslides using a physical determination model supports disaster prevention,but it is mostly applied to the area with few landslides,and there is a lack of quantitative study on rainfall and landslide stability.Therefore,we take the group-occurring landslide event(976 shallow landslides)in the Niangniangba basin,Gansu Province as a typical case.This paper combined the Scoops3D model with the TRIGRS model to predict the shallow landslide spatiotemporal distribution and compared the simulation results with those of the TRIGRS model alone,aiming to obtain more accurate assessment results.At the same time,the relationship between landslide stability and accumulative rainfall was quantitatively fitted to improve the real-time landslide prediction system.Finally,the better model was selected to simulate and predict the spatiotemporal distribution of landslide stability under three rainfall scenarios of continuous rain,short-term rainstorm and long-term heavy rainfall,and the influence of rainfall on landslide stability was discussed in combination with topography.The main conclusions are as follows:(1)Rainfall is the positive factor affecting the occurrence time and spatial distribution characteristics of shallow landslides.In the initial condition,the proportion of the extremely unstable area predicted by one-dimensional model and three-dimensional model is 4.03%and1.07%,respectively.While in the saturated condition,the proportion of extremely unstable area predicted by the two models increased significantly,accounting for 20.50%and 12.07%,respectively.(2)Both models have good applicability on the watershed scale of the loess areas.The%LRclass index of two models is 74.08%and 80.11%,respectively.The TRIGRS model has the limitation of over-prediction in the stable region,while the combination of TRIGRS and Scoops3D model can obtain more effective landslide prediction results with a smaller unstable region.(3)The relationship between instability proportion and accumulative rainfall in the 1D and 3D model can be represented byy(28)24.5 7x^0.18andy(28)11.5 9x^0.33,respectively.The 3D model is more dependent on rainfall and makes more accurate predictions.The rainfall threshold analysis proposed in this paper can provide reference for the time of most landslides in the case of insufficient data.(4)In the case of continuous rain,the landslide stability decreases with the increase of rainfall duration.In the case of short-term rainstorm,the stability of the landslide decreases with the increase of rainfall intensity,and the impact of the short-term rainstorm on the stability of the landslide is more obvious than that of continuous rain.The area of extremely unstable region under long-term heavy rainfall is higher than that under the other two scenarios,and the influence of rainfall intensity on slope stability is greater than that of continuous rainfall cycle.Combined with topographic analysis,steeper areas with slopes of15-30°and south-facing slopes are more susceptible to rainfall.