片麻岩类堆积层滑坡滑带土特性研究——以黄冈地区为例

Studying the Properties of Sliding Zone Soil in Gneiss Accumulation Landslide:A Case Study in Huanggang City

片麻岩是黄冈地区主要的孕灾地层,片麻岩类堆积层滑坡是黄冈地区主要的地质灾害类型,研究片麻岩类堆积层滑坡的滑带土特性对滑坡稳定性评价具有重要意义。选取黄冈地区8处典型滑坡为研究对象,将其分为两类滑坡(Ⅰ类——花岗质片麻岩堆积层滑坡,Ⅱ类——斜长片麻岩堆积层滑坡),采集滑带土样开展结构特征、物理性质和矿物组成等方面的研究。结果表明,在颗粒特征方面,黄冈地区片麻岩类堆积层滑坡的滑带土均呈现粗粒化,但Ⅰ类滑带土的砾粒和砂粒含量更高;在物理性质方面,两类滑带土均表现出含水率高、干密度低的特点,反映了滑带土内部黏结效果差、土体强度低;在矿物组成方面,两类滑带土均是以蒙脱石、累托石和伊利石为主的黏土矿物占比较高。直剪试验和正交试验表明,两类滑带土的黏聚力均值几乎相同,但Ⅱ类滑带土的内摩擦角均值有所增高;黏聚力和内摩擦角的影响因数从大到小依次为干密度、含水率和分维度。

Gneiss is the main disaster-prone formation in Huanggang area,and gneiss accumulation landslide is the main type of geological disasters.It is of great significance to study the characteristics of sliding zone soil of gneiss accumulation landslide for the evaluation and calculation of landslide stability.Eight typical landslides in Huanggang area were selected as the research object,and they were divided into two types(type I is granitic gneiss accumulation landslide,type II is plagioclase gneiss accumulation landslide).Soil samples were collected from the sliding zone to study the structural characteristics,physical property,mineral constituent and other characteristics.The results show that in terms of particle characteristics,the slip zone soils of gneiss accumulation landslides in Huanggang area are coarse-grained,but the gravel and sand contents of type I slip zone soils are higher;in terms of physical properties,both types of sliding zone soils show the characteristics of high water content and low dry density,reflecting the poor internal bonding effect and low soil strength of sliding zone soils.In terms of mineral composition,clay minerals dominated by montmorillonite,rectorite and illite account for a relatively high proportion in both types of slip zone soils.The direct shear test and orthogonal test design show that the mean value of cohesion of the two types of sliding zone soil is almost the same,but the mean value of internal friction angle of type II sliding zone soil is increased.The influence factors of cohesion and internal friction angle from large to small are dry density,moisture content and fractal dimension.