不同降雨条件下黄土高原浅层滑坡危险性预测评价

Risk Assessment and Prediction of the Shallow Landslide at Different Precipitation in Loess Plateau

黄土地区浅层滑坡发育非常广泛,由于其具有分布规律性差、前期变形迹象小、分布范围大、面小点多等特征,目前还无法进行有效预测,因此给黄土地区工程安全带来严重威胁。根据无限边坡模型,结合降雨入渗-土体强度衰减规律和GIS(地理信息系统)技术,构建了不同降雨条件下黄土地区浅层滑坡发育危险性评价模型,并将该评价模型应用到延河一级支流幸福川流域,预测在有效降雨量30、50、100、200mm条件下,该流域浅层滑坡发育程度,并与当前较为流行的SINMAP模型(地形稳定性模型)进行对比。结果表明:①不稳定和潜在不稳定浅层滑坡主要分布在末级河流的两侧和源头,稳定和较稳定区域主要分布在一级河流河道两侧和塬面上;通过对比分析,SINMAP模型计算的结果与本文建立的模型在降雨强度30mm时的计算结果较为一致。②在本文建立的模型评价结果中,随着有效降雨量的增加,Fs(稳定性系数)<1.00的不稳定区域所占比例逐渐增加,从30mm的1.12%到200mm的4.79%;相反,稳定区域则出现逐渐减少的趋势。③根据已发生灾害点的分布,随着有效降雨量的增加,研究区域已发生的灾害点分布在Fs<1.25的比例明显增加,从30mm的62%到200mm的88%,在SINMAP评价模型中,研究区域已发生的灾害点的64%分布在不稳定和潜在不稳定区域内,说明本文所建立的评价模型具有一定的精度。通过与SINMAP评价模型对比,本文建立的模型主要采用基于降雨入渗规律,而SINMAP评价模型主要基于降雨汇流过程,因此在利用过程中应根据区域特征选择利用。

The shallow landslide is universal in loess plateau with no distribution law and no distortion evidence.There is no good method to forecast the frequent occurrence of shallow landslide,causing risk to the residence,traffic and river ecology.The assessment and prediction formula of shallow landslide under different rainfall was established by means of the infinite slope model combined with rainfall infiltration-strength reduction law and GIS technology.Then the build assessment model was used to predict the landslide occurrence at the effective rainfall of 30 mm,50 mm,100 mm and 200 mm in Xingfuchuan watershed,a first tributary of Yanhe River.In order to check the applicability of the predict formula,it was compared with the popular assessment model of shallow landslide.The results are as follows： ①the instable and potentially instable shallow landslides are mainly distributed in both sides and source of the final class river,the stable and more stable region are mainly distributed in both sides of the first class river and highland surface;by comparing,the assessment results of SINMAP model are more consistent with the assessment results obtained by the predict formula built in this paper at the effective rainfall of 30 mm.②according to the assessment results obtained by the predict formula built in this paper,the area of unstable region（safe factor,Fs1） is gradually increased from 1.12% at the effective rainfall of 30 mm to 4.79% at the effective rainfall of 200 mm;on the contrary,and the stable region presents a decreasing trend.③according to the distribution of shallow landslides had occurred,the proportion of the happened shallow landslides that located in the unstable region are significantly increased with the growth of effective rainfall,from 62% at the effective rainfall of 30 mm to 88% at the effective rainfall of 200 mm;and 64% of the happened shallow landslides are located in the unstable region according to the assessment result of SINMAP model.So the assessment model built in this paper is more accurate compared with the SINMAP model.Finally,advantages and disadvantages of the established prediction formula in shallow landslide assessment in loess plateau were discussed.