西北某水电站泥石流发育特征及危险性评价

DEVELOPMENT CHARACTERISTICS AND RISK ASSESSMENT OF DEBRIS FLOW IN A HYDROPOWER STATION IN NORTHWEST CHINA

西北某拟建水电站下库泥石流沟具有流域面积大、沟谷切割深、沟道长度大等特点。其中东沟穿该抽水蓄能电站拟设下库而过,若爆发泥石流,会对主体工程施工和安全运行将造成严重威胁,因此有必要对该冲沟进行调查和泥石流评价。通过现场踏勘、试验,结合无人机解译和室内计算,对拟设电站下库东北侧泥石流沟发育特征及危险性进行分析和评价。研究结果表明:东沟沟道总长度2.89 km,流域周长7.37 km,流域面积2.15 km^(2),流域内高差近710 m,平均纵坡降约220.64‰,河道整体弯曲系数1.10;流域内物源总储量为17.59×10^(4)m^(3),以坡面侵蚀物源为主,其次为崩坡堆积物源,再次为崩塌堆积物源,沟道堆积物源最少。按设计暴雨频率1%计算,在拟设工程枢纽位置处,泥石流流速3.411 m/s,一次过流总量为3286.53 m^(3),一次固体冲出物质1250.88 m^(3),泥石流整体冲压力15.34 kPa,设计暴雨频率下单块块石按2 m计算,最大撞击力10.5 kN。东沟若发生泥石流,则将对下库工程及施工安全造成影响。

The debris flow gully in the lower reservoir of a proposed hydropower station in northwest China has the characteristics of large basin area,deep gully cutting and large gully length.The Dong gully passes through the planned storage of the pumped storage power station.If debris flow breaks out,it will pose a serious threat to the construction and safe operation of the main project.Therefore,it is necessary to investigate the gully and evaluate the debris flow.The development characteristics and risk of debris flow gully on the northeast side of the lower reservoir of the proposed power station were analyzed and evaluated through field survey and test,combined with UAV interpretation and indoor calculation.The results show that the total length of Dong gully Channel is 2.89 km,the basin circumference is 7.37 km,the basin area is 2.15 km^(2),the elevation difference within the basin is nearly 710 m,the average longitudinal gradient is about 220.64%o,and the overall bending coefficient of the channel is 1.10.The total provenance reserves in the basin were 17.59×10^(4)m^(3),with slope erosion as the main source,followed by slope collapse deposit,and then collapse deposit,and gully deposit was the least.Calculated according to the design rainstorm frequency of 1%,at the planned engineering hub location,the flow rate of debris flow is 3.411 m/s,the total amount of primary overflow is 3286.53 m,the primary solid outflow material is 1250.88 m^(3),the overall impact pressure of debris flow is 15.34 kPa,the design rainstorm frequency of a single block is 2 m,and the maximum impact force is 10.5 kN.If debris flow occurs in Dong gully,it will affect the engineering and construction safety.