西南某水电站闸址区右岸泥石流特征及其工程效应研究

Study on characteristics and engineering effects of debris flow on the right bank of a hydropower station,southwest of China

西南某水电站闸址区右岸三坪子沟,历史上曾多次发生泥石流活动。通过现场系统调查和室内的综合分析认为,该泥石流的特点如下:①地处扬子板块西缘(槽台结合部位),小流域主要出露浅变质的三叠系岩层,岩体经历多期强烈变形,具有复杂的构造背景;②小流域内见11条不同规模的断层,并发育多组节理,岩体破碎,有利于次生改造;③新构造活动强烈,第四纪以来抬升幅度大,多在2mm a以上;④降雨丰富,年降雨达1000mm以上,而且集中在6～9月份;⑤泥石流形成区汇水面积大,崩坡积及洪积物发育,物源丰富;⑥流通区窄陡,有利于泥石流的加速;⑦堆积区位于离沟口上游2km的古堰塞湖内;⑧由于沟口泥石流搬运的大部分固体物质未到沟口就已堆积下来,然后被携沙水流所代替;⑨该泥石流沟仍有发生泥石流的可能性;⑩三坪子沟100a一遇泥石流输送到雅砻江的泥沙量在3×104m3以下。因此,即使未来发生100a一遇的泥石流,对上、下闸址也不会构成直接威胁。

Sanpingzi valley on the right bank in the dam site region of a hydropower station,southwest of China,there were many debris flow events happened in the history.Based on engineering geological survey and comprehensive analysis,the authors think that the main characteristics of these debris flows are as follows:①The debris flow valley is located in the western boundary of Yangtze plate (transition belt of the Songpan-Ganzi geosyncline fold system and Yangtze platform),which mainly consists of Triassic schist,marble,slightly metamorphical sandstone,slate,and Quaternary accumulations,and where the rockmass has been undergone many tectonic movements,and the tectonic background is complicated;②11 different-scaled faults can been found in the valley,texture surfaces(at least 4 sets of texture surfaces)are well developed,and the rockmass is fragmented and easy for secondary alteration;③The neotectonic is intensive,which has been uplifted quickly since Quaternary,and over 2mm/a uplift velocity formed typical canyon Landform;④Rain fall in the region is rich and can reach 1000?mm/a,which is mainly concentrated in June-September;⑤The prevenance of the debris flow is large,and colluvial and slope wash are well developed,which can provide rich material resources for the debris flow;⑥Flow section of the debris flow is narrow and steep,being good for the acceleration of it;⑦The accumulative region of the debris flow is located at Sanpingzi,2?km upstream from the valley mouth,rather than the accumulative region of a common debris flow located at the valley mouth area.⑧As most solid material of the debris flow is accumulated in Sanpingzi,then instead by flow slightly with sands and gravels in the downstream;⑨As there are favorable conditions for the debris flow formation mentioned above,a debris flow may happen in the future,⑩A debris flow of once 100 years just transports 3×10~4?m^3 solid material to Yalong River,therefore,even the future debris flow of once 100 years happens in Sanpingzi valley,it will not strongly influence the upper and lower lock location.