川西松潘黄土发育特征与工程地质力学特性分析

ANALYSIS ON THE DEVELOPMENT CHARACTERISTICS AND ENGINEERING GEOMECHANICAL PROPERTIES OF THE SONGPAN LOESS,WESTERN SICHUAN PROVINCE,CHINA

以松潘幅和漳腊幅1∶5万工程地质调查为基础,通过野外地质调查、地质测年、地理空间分析、室内试验和大型原位直剪试验等工作手段,对松潘黄土的发育分布特征和工程地质力学特性进行研究分析,认为松潘黄土具有以下特性:(1)松潘黄土为风成黄土,局部地形的变化通过控制近地面气流的运动从而影响松潘黄土的堆积,使得松潘黄土的分布与研究区地形、地貌的变化联系密切;(2)松潘黄土粉砂含量大于80%,大多含有碎石,碎石物质成分主要以砂板岩、炭质板岩和石英为主;(3)研究区内的松潘黄土主要分布于2712~3437 m的高程范围内,在山体南坡的分布远多于北坡,在地形开阔的断陷盆地内,黄土发育厚度大且呈广泛连续式分布,在高深的峡谷区,黄土的发育厚度变化大且呈零星的片状分布;(4)松潘黄土结构性明显,其力学性质受物质成分、含水率和天然结构面的影响,具有中等—强的湿陷性,黄土的结构性、水敏性、湿陷性等性质是该套地层内地质灾害发育的主要因素,松潘黄土的不良工程地质特性严重影响着研究区内未来重大工程的规划建设。

Based on the 1 ： 50000 geological survey of Songpan map and Zhangla map, t h r o u g h th e field geological survey, geological dating, geography space analysis, laboratory test and in-situ large scale direct shear test, the development and distribution characteristics and engineering geomechanical properties of the Songpan loess are studied in this article. The Songpan loess has the following features ： （ 1 ） T h e Songpan loess is an eolian deposi tand the changes of local terrain affect the accumulation of the Songpan loess by controlling the movement of the air near the ground. So the distribution of the Songpan loess is closely related to the topography and geomorphology of the study area. （2） The Songpan loess contains more than 80% silt and mostly with gravels, and the material composition of gravels mainly are sandy slate, carbonaceous slate and quartz. （3） The Songpan loess in the study area is mainly distributed within the scope of elevation between 2712 ？2712 m, mostly in the south slope of the mountain, within the broad fault basin. It has a large and extensive continuous distribution, while in the deep canyon area with a patchy distribution. （4） The Songpan loess has a distinct structure, and its mechanical properties are influenced by material composition, moisture content and natural structure plane, with an intermediate to high collapsibility. The loess characteristics of structure, water sensitivity and collapsibility are the main factors in the development of geological disasters in the strata and the construction of the future major projects in the research area will be influenced by the undesirable engineering geological characteristics and geological disasters of the Songpan loess.