岷江上游叠溪古堰塞湖溃坝堆积体的沉积特征及溃决洪水反演

发布时间：2018-03-07 08:58

本文选题：古堰塞湖　切入点：溃坝堆积体　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：滑坡堰塞坝的形成是一个快速堆积的过程,其物质来源非常复杂,使得坝体结构松散、杂乱,易发生溃决事件,形成“溃坝堆积体”。作为地貌学和沉积学等地质地貌信息的物质载体,溃坝堆积体是研究古堰塞湖沉积环境、溃决演进过程和古洪水动力学及山区地质环境演化规律的一个重要途径,对于古环境重建和地质灾害防治具有十分重要的现实指导意义。叠溪古堰塞湖位于岷江上游叠溪河谷段(叠溪古镇至上游太平村附近),全长约30 km,其下游发育长约5 km的天然溃坝堆积体,规模实属罕见。本文综合运用野外地质调查、测量采样、室内试验及定量计算等方法,深入分析叠溪古滑坡堰塞湖溃坝堆积体的沉积特征和粒度特征,并对溃决洪水进行了定量反演研究,最后对叠溪古滑坡堰塞湖的成因及溃决事件发生的年代进行了分析。本研究得到以下认识和成果:(1)叠溪古堰塞湖溃坝堆积体是由高流态灾难性洪流及常态流和河流态机制形成的。这些堆积体具有叠瓦构造、孔洞构造、块状构造、杂基构造、支撑—叠置构造及韵律互层构造。溃坝堆积体具有两大类沉积相——巨砾层相(Bcm)及砾石层和砂层相(Gm、Gfm、GRm、Sh、St/Sp),每个巨砾层相代表一个高流态沉积事件,而砾石层相和砂层相则是由脉动流形成的。(2)叠溪古滑坡堰塞湖溃坝堆积体的粒度主要由巨砾、砾石(细~粗)、砂(极细~粗)、粉砂和粉土及少量的黏土物质组成,其中,松散粗大的块石成分很可能来源于上游坝体物质,而细粒成分则可能来自坝体物质、坝体上游的湖相沉积物或者河床物质等。(3)叠溪溃坝堆积体具有很好的粒度分形特征和统计自相似性。从上段至下段,堆积体粒度分维值呈依次减小的趋势。(4)推断叠溪古滑坡堰塞事件是由古地震活动引发的。堰塞湖形成后在全新世早期(10~40 ka BP之间)发生了溃决。经水动力学中的水流能量法估算,叠溪古滑坡堰塞湖溃口处溃决洪水平均流速为17.23 m/s,洪峰流量为49821.28m3/s,是岷江常年流量的数十倍。
[Abstract]:The formation of landslide damming dam is a fast accumulation process, the material source is very complex, the dam structure is loose, messy, prone to outburst events, the formation of "dam accumulation body". As the material carrier of geomorphology and sedimentology geological information, dam accumulation is of ancient sedimentary environment of a lake. An important way to break the evolution process and the ancient geological environment and mountain flood dynamic evolution law, has very important practical significance for the reconstruction of the paleo environment and geological disaster prevention. The Diexi ancient dammed lake of Minjiang River Valley is located in Diexi (near Diexi town to the upper reaches of Taiping Village), a total length of about 30 km and its downstream development the natural dam about 5 km long accumulation, the scale is rare. This paper used comprehensive field geological investigation, sampling, laboratory test and quantitative calculation methods, in-depth analysis of ancient landslide damming Sedimentary characteristics and grain size characteristics of the accumulation body lake dam, and the flood of quantitative inversion, formation of the ancient landslide lake and finally break the chronology of events was analyzed. The following achievements obtained in this study: (1) the Diexi ancient dammed lake dam accumulation body is formed by high flow and normal flow and catastrophic flood river flow mechanism. These accumulation has imbricate structure, pore structure, block structure, matrix structure, support overlay structure and rhythmic interbed structure. The dam accumulation has two types of sedimentary facies: giant gravel layer (Bcm) and gravel layer and sand phase (Gm, Gfm, GRm, Sh, St/Sp), a high fluid phase deposition events representing each layer of gravel and boulders, sand and phase are formed by pulsating flow. (2) ancient landslide lake dam break pile size is mainly composed of boulders, gravel, coarse (fine (very), sand Fine to coarse silt and silt), and a small amount of clay material composition, the composition of thick loose stone probably derived from the upstream dam material, and fine ingredients may come from the dam material, dam upstream of lake sediments or bed material. (3) the Diexi dam body has accumulated grain size fractal characteristics and good statistical self similarity. From upper to lower, accumulation of grain size fractal dimension showed a decreasing trend. (4) concluded that ancient landslide damming events are caused by the paleo earthquake. After the lake formed in the early Holocene (10~40 Ka BP) occurred the estimation by the water outburst. The energy method in water dynamics, ancient landslide dammed lake outburst flood breach average flow rate is 17.23 m/s, the peak flow is 49821.28m3/s, ten times Minjiang perennial flow.

【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.2

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