万州西溪铺松散堆积体成因分析及稳定性评价

根据勘探钻孔资料,对西溪铺一带松散堆积体的特征及成因进行了详细的探讨.研究结果表明:分布在基岩面高程190m以下的斜坡与基岩面高程140～150 m平台上的粉质黏土夹碎石土层是由滑坡作用形成的(即西溪铺滑坡);分布在基岩面高程190 m以上的粉质黏土夹碎石土层是由崩积、残积及坡积作用形成的;卵石砂土层是苎溪河的冲积作用形成的.对西溪铺滑坡的形态、滑动面特征、水文地质条件及形成年代等进行了论述,这些特征说明西溪铺滑坡曾发生过一次大型的堆积体滑动、多次小型的表层滑动,其是在一级阶地形成时代T1以后的几千年之内形成的.根据下伏卵石砂土层的地质结构,对西溪铺滑坡的稳定性进行了评价,评价结果表明库水位的变化对西溪铺滑坡的稳定性有巨大的影响,在滑坡的防治设计中必须引起高度的重视.

Mechanism Analysis and Stability Assessment of Xixipu Soil Deposits in Wanzhou

The paper firstly discusses the characteristics and mechanism of Xixipu soil deposits based on the material of 98 boreholes. The results show that these gravel silty clays distributed at the range between the rock slope with an altitude lower than 190 m and the rock platform with an altitude about 140-150 m are formed from sliding (called Xixipu landslide) ;and that those gravel silty clays distributed above 190 m of the rock surface are residual, colluvial and talus deposits; and that the gravel sand layer located along Zhuxi River is a kind of alluvial deposit. Then the paper studies in detail the characteristics of configuration, sliding surfaces,hydrogeology,and forming time of Xixipu landslide. It is proved that a large scale of landslide and several small scale landslides have occurred in Xixipu,and the sliding time is after Terrace 1, within several thousand years. Finally,based on the geological structure underlain by gravel sand,it calculates the stability factors of Xixipu landslide with the remained slip force method under several water conditions. The results show that the variation of water level in Three Gorge Reservoir has significant influence on the stability of Xixipu landslide. Therefore, great attention should be taken to Xixipu landslide in the prevention design.