基于覆盖土层厚度识别的区域斜坡降雨入渗稳定性定量评价

Regional Hillslope Stability Analysis under Rainfall Based on Characterization of Overburden Soil Layer Thickness

区域内覆盖土层孕育着斜坡浅表层破坏,是区域斜坡破坏的最主要来源,但由于覆盖土层厚度的空间变化,导致堆积层滑坡灾害发育的底界难以合理确定,进而使稳定性评价结果未能指示实际滑坡状况.以黄冈市九资河镇为例,对该区域的覆盖层厚度进行详细调查,并通过基于地貌过程的估计方法确定了研究区覆盖层厚度的空间分布;在此基础上,运用斜坡稳定性定量模型,分析了研究区斜坡在降雨条件下的稳定性,并据此估计了区域堆积层滑坡的分布情况和可能性.结果显示:所提出的方法有效且具有很强的实用性,基于GIST模型估计的区域覆盖层厚度与实际情况较为接近(集中在0.5~3.0 m).覆盖层厚度的合理确定使得区域斜坡降雨入渗稳定性评价结果更加精细且具有实际滑坡指示意义;该区基本稳定和稳定斜坡主要分布于阶地平台或河漫滩等覆盖层厚度大但坡度较小区域,欠稳定及不稳定斜坡主要分布在水库及各支流靠岸位置,这些部位覆盖层厚度虽小但坡度较大、地形外凸且受地下水影响明显;短时间的强降雨对斜坡稳定性影响巨大.该研究有助于推动区域斜坡灾害评价向精细化方向发展.

The overburden layer in the region conceives the shallow surface damage of slopes and is the main source for the regional slope damage.But,the spatial variation in the thickness of the overburden layer makes it difficult to reasonably determine the bottom of hazard development,which in turn makes it difficult for the stability assessment results to indicate actual landslide conditions.Taking Jiuzihe Town of Huanggang City as an example,the overburden thickness in this area was investigated in detail,and the spatial distribution of overburden thickness was determined by a geomorphic process-based method.On this basis,the stability of slopes in the study area under rainfall conditions was analyzed using a quantitative model of slope stability,and the distribution and likelihood of regional accumulated layer landslide were estimated accordingly.The results show that the proposed method is effective and highly practical,and that the estimated regional overburden thickness based on GIST model is close to the actual situation,mainly concentrated in 0.5-3.0 m.The reasonable determination of overburden thickness makes the evaluation results of regional slope rainfall infiltration stability more precise and has practical landslide indication significance.The basically stable and stable slopes are mainly distributed in the areas with large overburden thickness but small slope,such as terrace platform or floodplain.While the less stable and unstable slopes are mainly distributed in the reservoir and the bank of various tributaries.Short period of heavy rainfall has great influence on slope stability.This study is helpful to the development of regional slope disaster assessment towards the fine direction.