A Study on the Threshold Model of Landslide Rainfall in Chongqing Based on Different Geological Environment Zones
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摘要: (目的)考虑区域历史滑坡的降雨特征与地质环境,构建合理的降雨阈值模型,对区域滑坡灾害的预测预报十分重要。(方法)本文以重庆市2013-2021年的1368个降雨型滑坡为研究对象,基于详细的滑坡编录数据和区域地质环境资料,划分降雨事件,构建滑坡样本库。利用随机森林(RF)算法,建立了当日激发降雨量-前期有效降雨量(Rd-Rp)降雨阈值模型,基于概率分级划分了不同预警等级。以中等预警概率按孕灾环境、工程岩组、土地利用和土壤类型四种地质环境分别构建了19个临界降雨阈值判据。(结果)结果表明:Rd-Rp阈值模型能够很好的反映当日激发降雨和前期有效降雨对滑坡发育的影响,且前期有效降雨量在滑坡诱发中占主导作用。不同的地质环境类型对降雨因子的敏感性不同,地质构造、岩土体工程性质、植被覆盖以及土壤性质等对滑坡发育有重要影响。以坚硬岩为主的岩组阈值高于以软弱岩为主的岩组,林地的阈值大于耕地,受人类工程活动破坏严重的区域阈值会降低。(结论)本文利用随机森林方法为重庆市不同地质环境分区建立了降雨阈值判据,本研究可为重庆市降雨型滑坡的气象预警管理方面提供新的思路与借鉴依据。Abstract: Considering the rainfall characteristics and geological environment of historical landslides in the region, it is important to construct a reasonable rainfall threshold model for the prediction and prediction of regional landslide disasters. In this paper, 1368 rain-induced landslides in Chongqing from 2013 to 2021 were selected as the research objects. Based on detailed landslide cataloging data and regional geological environment data, rainfall events were divided and landslide sample database was constructed. Based on Random forest (RF) algorithm, a rainfall threshold model of the day's triggered rainfall - previous effective rainfall (Rd-Rp) was established, and different warning levels were divided based on probability classification. Based on the medium early warning probability, 19 threshold criterions of critical rainfall were constructed according to four geological environments, namely disaster pregnant environment, engineering rock group, land use and soil type. The results show that the Rd Rp threshold model can well reflect the impact of the daily excitation rainfall and the early effective rainfall on the landslide development, and the early effective rainfall plays a leading role in the landslide induction. Different geological environment types have different sensitivity to rainfall factors, and tectonics, engineering properties of rock and soil mass, vegetation coverage and soil properties have important effects on landslide development. The threshold of rock formations mainly composed of hard rocks is higher than that of rock formations mainly composed of soft rocks, and the threshold of forest land is higher than that of cultivated land. The threshold of areas severely damaged by human engineering activities will decrease. The study can provide new ideas and reference for the meteorological early warning management of rainfall landslides in Chongqing.
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