粘性泥石流堵江的临界条件实验研究
本文选题:泥石流 + 堵江 ; 参考:《成都理工大学》2017年硕士论文
【摘要】:泥石流是我国山区常见的自然灾害现象,是一种介于滑坡和水流之间的含泥、沙和石块的固、液两相流体,具有爆发突然、运动快速、历时短暂等活动特点,呈紊流和层流的运动状态。含有大量固体物质的粘性泥石流体进入主河以后,受到主河水动力条件和地形条件改变的影响,在交汇处发生淤积形成堆积坝,如果泥石流入汇总量和堆积坝体抗冲击力足够,则有可能发生堵江现象,形成堰塞湖,引发更加严重的灾害链效应:堰塞湖导致上游水灾,溃决后大规模洪水。我国的堵江型泥石流以粘性泥石流为主。近十年来,受地震和极端天气影响,堵江型泥石流的防治已经成为地质灾害防治领域的热点。目前对泥石流堵江的研究方法,多分为三种。一为通过室内水槽实验研究相关影响因素的关系得到堵江判别式。二是通过统计学对已有堵江事件进行分析,得到相关的统计模型。三是进行理论分析,建立基于动量动能的理论力学模型。现行的研究方法各有利弊,存在主要的问题有:判别式的因子选取考虑不全或是选取上存在重复;未对堵江结果定量分析,判别式计算结果以定性为主;对于泥石流的流体性质在灾害中的效用的相关研究不足。本文针对现有研究的不足,引入屈服应力作为描述泥石流体流体性质的指标,对泥石流流体性质的作用进行了进一步探讨。以体积因子V表述泥石流规模与沟床的关系、单宽流量比r表述支沟与主河的冲淤条件、屈服应力因子τ表述泥石流的流体性质、入汇角因子J表述支沟与主河的交汇情况,通过室内水槽实验控制变量,结合野外数据验证,得到可以定量分析堵江结果的临界条件判断式,本文得到结论如下:(1)屈服应力较大的泥石流流体形成的堆积坝在抵抗主河水流扰动和抗冲刷能力上更好,利于堵江发生。反之则不利于堵江的发生。(2)泥石流汇入主河以后,入汇总量必须达到一定标准才能发生堵断主河现象。这个入汇总量与交汇处主河的水深以及主河的宽度有关。较小的河床容量(主河宽度、水深较小)和较大的泥石流入汇总量有利于堵江的发生。(3)大单宽流量比条件下的泥石流可以在主河宽度方向上运动更长的距离,且形成的堆积坝会阻碍主河水流的运动造成上游壅水。小单宽流量比条件下的泥石流不仅在主河宽度方向上运动距离有限,较难形成规模强度足够的堆积坝。(4)泥石流锐角入汇主河时,主河水流可以较容易的侵蚀和搬运泥石流流体,不利于堵江的发生;钝角入汇主河时,泥石流流体大量淤积在交汇处,难以被搬运和侵蚀,利于堵江的发生。(5)通过将影响因素简化为无量纲因子:τ、V、r、J,通过水槽实验控制变量得到因子关系,得到的最终模型为:P =τ0.9×V×r1.1×J0.78,当P≥0.93时有可能发生全堵;当0.6 ≤P 0.93时,有可能发生大部分堵塞;当0.32≤P0.6时,有可能发生局部堵塞;P0.32时,发生堵江可能性较低。本文通过使用实地考察获得的野外数据结合文献记载对公式进行了验证,确认该模型具备较好的普适性和可靠性。
[Abstract]:Debris flow is a common natural disaster phenomenon in the mountain area of China. It is a solid, liquid two phase fluid, which consists of mud, sand and rock between landslides and currents. It has the characteristics of sudden eruption, rapid movement, and short period of movement. It is turbulent and laminar flow. After the viscous debris fluid containing a large amount of solid material enters the main river, it is subjected to the main river. The influence of the dynamic conditions of the main river and the change of the topographic conditions at the intersection and formation of the accumulation dam. If the aggregate amount of the debris flow and the anti impact force of the accumulated dam are sufficient, the phenomenon of blocking the river may occur, forming the weir lake and causing a more serious disaster chain effect: the weir plug Lake leads to the upstream flood and the large-scale flood after the burst. Our country In the past ten years, the prevention and control of the debris flow of the river block has become a hot spot in the field of geological disaster prevention and control. At present, there are three kinds of research methods for debris flow blocking the river. One is to get the discrimination of the river block through the relationship between the related factors of the laboratory water trough experiment. Two is to analyze the existing river blocking events through statistics and get the relevant statistical models. Three is to carry out theoretical analysis and establish a theoretical mechanics model based on momentum kinetic energy. The current research methods have advantages and disadvantages, and the main problems are: the discriminant factor selection is not considered or the selection is repeated; the result is not the result of the river blocking. Quantitative analysis, the result of the discriminant calculation is mainly qualitative; the relative research on the utility of the fluid properties of debris flow is insufficient. In this paper, in view of the shortage of the existing research, the yield stress is introduced as an index to describe the properties of the fluid fluid in the debris flow, and the effect of the fluid properties of the debris flow is further discussed. The volume factor V table is used. The relationship between the scale of debris flow and the trench bed, the single wide flow ratio R expresses the conditions of the branch gully and the main river's erosion and siltation, the yield stress factor tau expresses the fluid properties of the debris flow, and the convergence angle factor J expresses the intersection of the branch ditch and the main river, and through the laboratory control variables and the field data verification, the quantitative analysis of the result of the river blocking can be obtained. The conclusion of this paper is as follows: (1) the accumulation dam formed by the debris flow fluid with large yield stress is better to resist the disturbance and anti scouring ability of the main river, which is beneficial to blocking the river. (2) after the debris flow into the main river, the total amount of sinks must reach a certain standard to block the main block. The total amount of this sink is related to the depth of the main river at the intersection and the width of the main river. The smaller size of the river bed (the width of the main river, the less water depth) and the amount of the larger debris flow are beneficial to the occurrence of the river blockage. (3) the debris flow under the condition of large single width flow ratio can move longer in the direction of the main river, and the formation of the heap The dam will obstruct the upstream flow of the main river flow. The debris flow under the small single width flow ratio is not only limited in the main river width, but it is difficult to form a large scale strength accumulation dam. (4) when the debris flow sharp angle enters the main river, the main river flow can easily erosion and transport the debris flow fluid, which is not conducive to blocking the river. When the obtuse angle enters the main river, the debris flow is deposited at the intersection, and it is difficult to be transported and eroded to block the occurrence of the river. (5) by simplifying the influence factors into dimensionless factors: tau, V, R, J, the final model is obtained through the control variables of the trough experiment, and the final model is: P = tau, tau, V * r1.1 x J0.78, when P is more than 0.93. When 0.6 less than P 0.93, most plugging may occur. When 0.32 is less than P0.6, local blockage may occur. When P0.32, the possibility of blocking the river is low. This paper verifies the formula by using field data obtained by field investigation combined with literature to confirm that the model has good universality and reliability.
【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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