泥石流底部侵蚀作用影响因素水槽实验研究

发布时间：2018-05-12 21:48

本文选题：泥石流 + 松散堆积体　；参考：《成都理工大学》2017年硕士论文

【摘要】：四川汶川“5.12”大地震震后在地震重灾区引发了多种次生地震灾害,其中尤其以泥石流影响最为严重。地震中以及震后大量的崩塌、滑坡都会在沟道中形成大量松散堆积体的累积,这也为泥石流在爆发后运移过程中规模的不断扩大提供了丰富的物质条件。本文在资料查阅、野外现场勘察的基础上,以震后沟道松散堆积体为研究对象,采用室内水槽模拟实验,对泥石流底部侵蚀作用的相关影响因素进行研究。通过大量物理实验,获得泥石流对沟道底部侵蚀作用与初期泥流浆体浓度、沟道坡度及初始含水率等因素的关系,主要研究成果如下:(1)泥浆流经铺满松散砂料的沟槽时,可以形成挟带大量颗粒并在前端有明显陡立的龙头,且龙头速度远小于后续流体流速。这一现象随坡度、泥浆浓度的改变而改变。当坡度较大时,泥浆冲刷作用明显,流体前峰会有明显隆起的龙头,且龙头内固体颗粒含量较高;当坡度较小,或泥浆浓度较大时,泥流前峰不会形成龙头,且前峰中几乎不含固体颗粒。(2)实验过程中,泥浆入流初期,浆体动能较大,在实验槽上部的松散堆积体中迅速冲蚀,被泥浆冲刷带走的固体颗粒混入浆体继续向下运动,进而在后续运移冲刷过程中表现为下切侵蚀。整个模式表现为逐渐侵蚀加剧,所形成的泥石流容重不断增加。(3)浆体浓度、沟槽坡度可以影响泥石流的入渗能力和侵蚀速率。仅考虑浆体浓度的影响时,随着浆体浓度的增加,泥石流在沟道松散堆积物的入渗能力降低,侵蚀速率减小,侵蚀量也随之减小;仅考虑坡度的影响时,坡度不仅会影响泥石流起动的临界流量,也会显著影响泥石流作用于沟床底部的侵蚀作用。坡度越大,浆体对松散堆积体的侵蚀速率越大,泥石流的后期规模也会越大。(4)除了浆体浓度、沟床坡度外,沟道松散堆积体的初始含水率也会显著影响泥石流流经沟道时的流动性和入渗能力,从而影响泥石流的侵蚀速率,相对于含水率较高的松散堆积物,干性砂料更容易被浆体吸附并随泥浆运移;浆体内的细小固体颗粒会进入松散堆积体的原生骨架并与其结合形成级配较好的相对稳固的堆积体,这会使泥浆的侵蚀能力降低。
[Abstract]:After the May 12 earthquake in Wenchuan, Sichuan Province, it caused many secondary earthquake disasters, especially debris flow. During and after the earthquake a large number of collapses and landslides will form a large number of loose accumulations in the channel which provides abundant material conditions for the continuous expansion of the scale of debris flow in the process of migration after the eruption. Based on the reference of data and field investigation, this paper takes the loose accumulation body of channel after earthquake as the research object, and uses the indoor flume simulation experiment to study the influence factors of debris flow bottom erosion. Through a large number of physical experiments, the relationship between the erosion of debris flow to the bottom of the channel and the initial mud slurry concentration, channel slope and initial moisture content is obtained. The main research results are as follows: 1) when the mud flows through the channel filled with loose sand, A large number of particles can be formed with a sharp front end, and the faucet velocity is much smaller than that of the subsequent fluid flow rate. This phenomenon changes with the change of slope and mud concentration. When the slope is high, the mud scour is obvious, and there is a clear bulging faucet at the pre-fluid summit, and the solid particle content in the tap is higher; when the slope is low or the mud concentration is high, the faucet does not form at the mudflow front peak. In the process of the experiment, the kinetic energy of the slurry is larger at the initial stage of the mud flow, and the slurry is rapidly eroded in the loose accumulations in the upper part of the experimental tank, and the mixed solid particles removed by the mud continue to move downward. And then in the course of subsequent migration erosion, it is shown as undercutting erosion. The whole model is characterized by gradually increasing erosion and increasing bulk density of debris flow. The slope of groove can affect the infiltration capacity and erosion rate of debris flow. Considering only the effect of slurry concentration, the infiltration ability of debris flow in the channel loose accumulation decreases, the erosion rate decreases, and the erosion amount decreases with the increase of slurry concentration. The slope will not only affect the critical flow of debris flow starting, but also affect the erosion of debris flow at the bottom of trench bed. The larger the slope, the larger the erosion rate of the slurry to the loose accumulation, and the larger the scale of debris flow in the later stage. The initial moisture content of the channel loose accumulation also significantly affects the fluidity and infiltration ability of debris flow through the channel, thus affecting the erosion rate of debris flow, relative to the loose accumulation with higher water content. Dry sand is more easily adsorbed by the slurry and transported with the slurry, and the fine solid particles in the slurry will enter the primary skeleton of the loose accumulation and combine with it to form a relatively stable accumulation with better gradation, which will reduce the erosion ability of the slurry.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.23

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