金沙江其宗河段河床深厚覆盖层特征及其工程效应研究  

A study on the characteristics of deep overburden in Qizong segment of Jinsha River and its engineering effects

作　　者：王运生[1] 邓茜[1] 罗永红[1] 王自高 高建 吴俊峰[1] 孙刚[1] 

机构地区：[1]成都理工大学地质灾害防治与地质环境保护国家重点实验室,成都610059 [2]中国水电顾问集团昆明水电勘测设计研究院,昆明650051

出　　处：《水文地质工程地质》2011年第1期40-45,64,共6页Hydrogeology & Engineering Geology

基　　金：国家自然科学基金项目(中国西部深切河谷谷底卸荷松弛带形成机理及其工程效应研究;40472143/D0214)

摘　　要：金沙江其宗河段发育60～120m的河床深厚覆盖层。深厚覆盖层纵向上可分为三大层:河床底部为卵(块)砾(碎)石层夹中细砂或粉质粘土,为冲积及冰水堆积成因(al+fglQ3),厚11.1～33m;中部为细砂、粉细砂、粉质粘土层及卵(块)砾(碎)石层,该层为加积层,由冲积、泥石流堆积、洪积、崩坡积、堰塞多成因堆积组合而成(al+pl+sefQ3),厚10.04～35m;中上部为漂(块)卵(碎)砾石夹砂层透镜体,冲积堆积形成(alQ3-4),厚9.5～59m。河床覆盖层中的砂层透镜体分布范围广泛,埋藏深,最大埋深达83.1m,最大厚度达到29.4m,最小厚度仅0.5m,一般厚度在5m以内。研究表明砂层不具有湖相堆积的特征,而是相对静水环境条件下及正常河流漫滩相等堆积形成。通过原位及室内取样试验表明,其宗河段河床覆盖层中粗粒土(漂(卵)碎块石等)强度相对较高,中下部细粒土工程性质具有超固结性,不具液化性,上部细砂层强度较低,地震工况下可能液化。该河段深厚覆盖层的工程效应主要有坝基地质条件差,仅适合堆石坝、坝基开挖方量大、砂层处理深度大、防渗处理难度较高等。Overburden of 60-120m deep is developed in the Qizong segment of Jinsha River.The deep overburden can be divided into three layers upward.Pebble and gravel intercalated with minor fine sand or silty clay with the thickness of 11.1-33m at the bottom of the riverbed;a layer of fine sand,silty clay,pebble and gravel which with the thickness of 10.04-35m in the middle of the riverbed;coarse lenses of the drift（blocks）,pebble（broken） and gravel layer with the thickness of 9.5-59m in the upper part.Sand lens are widely distributed in the deep overburden.The maximum buried depth is 83.1m,the maximum thickness is 29.4m,and the minimum thickness is only 0.5m.The thickness of the sand lens is generally within 5m.Studies show that the sand lens is not formed by the accumulation of lacustrine,but is formed by accumulation of the relatively still water environment and the normal river floodplain.By indoor sampling tests,it shows that coarse-grained soil（boulder-pebbles accumulation,etc.） in the overburden of the river bed is relatively strong and hard,fine-grained soil in the lower place is excess consolidated,but non-liquefaction.Fine sand lens at the upper are relatively weak,so it is possible to be liquefied under an earthquake.The engineering effects can be concluded that because of the bad geological conditions it is only suitable for rock-fill dam,the excavated volume is huge,the sand layer treatment depth is large and impermeable treatment is quite difficult.

关 键 词：深厚覆盖层 发育特征 工程效应 金沙江 

分 类 号：P642.2[天文地球—工程地质学]