大渡河色斯满沟泥石流形成条件及风险性评价

Formation Mechanism and Risk Assessment of Debris Flow in Sesiman Gullyof Daduhe River

色斯满沟为大渡河上游右岸一级支流,由于该沟在历史上曾发生过泥石流,因此其沟口处水电站工程的安全问题成为关注焦点。通过野外详细调查和室内综合分析,探讨了该沟泥石流基本特征和形成条件,并进行了风险性评价。研究探明:色斯满沟主要出露燕山期花岗岩,风化程度低,但末次冰碛物发育,沟口堆积扇主体形成于晚更新世末次冰期;全新世以来,因水源条件发生了较大变化,以低频泥石流为主;在极端降雨、地震及沟道等多因素耦合条件下,色斯满沟可暴发大规模堵溃式泥石流。对色斯满沟进行泥石流风险评价,结果为高度风险泥石流沟。

Sesiman gully is the main tributary at the right bank of upstream of Daduhe River.Debris flow occurred in the gully,thus the security of hydropower station at the gully entrance is an important problem.In this paper,on the basis of field investigations and comprehensive laboratory analysis,the formation conditions and risk assessment of debris flow in the Sesiman gully were discussed.The results showed that（1）the host rock of Sesiman gully is Yanshanian granite which has low weathering degree,but the glacial till is well developed and the main deposit fan at the gully entrance was formed in Last Glacial of Late Pleistocene;（2）the hydrologic conditions have varied significantly with the occurrence of low-frequency debris flow since Holocene;and（3）a huge dam-breaking debris flow can occur under the conditions of earthquake and extreme rainfall.The risk assessment results of debris flow in the Sesiman gully indicated that the gully has high risk of occurrence of debris flow.