泥石流平衡坡度的试验研究

发布时间：2018-04-10 10:16

  选题：泥石流　视角：平衡坡度　引自：《成都理工大学》2017年硕士论文

【摘要】：泥石流是我国西南山区常见的地质灾害之一,具有爆发突然、运动快速、能量巨大、冲击力强、破坏性大等特点,冲和淤是其主要危害。泥石流的平衡坡度是指泥石流在运动过程中,泥石流的表面流速在沟床内达到一个定值,泥石流对沟床的影响为不冲不淤状态时的沟床坡度。泥石流排导槽是泥石流灾害治理的主要工程手段之一,排导槽的坡度是排导槽设计的重要指标。排导槽的设计坡度就是泥石流的平衡坡度:当排导槽的坡度大于泥石流的平衡坡度时,泥石流对排导槽的影响为冲刷,将缩短排导槽的使用寿命;当排导槽的坡度小于泥石流的平衡坡度时,泥石流将在排导槽内淤积,达不到排导效果。所以,进行泥石流平衡坡度的研究将对泥石流排导槽坡度的设计具有指导作用。泥石流的平均流速是对泥石流评估和防治最重要的参数之一。在野外观测中,泥石流的平均流速难以获得,而表面流速的获得相对容易,通过两者的关系可以将表面流速换算成平均流速。所以,进行泥石流平均流速与表面流速之比的研究也很重要。前人对泥石流平衡坡度和平均流速与表面流速之比的研究,考虑的影响因素主要集中在泥石流的性质或运动特征上,忽略了泥石流沟床对泥石流平衡坡度及平均流速与表面流速之比的影响,研究成果较难满足复杂多变的野外情况。针对前人研究的不足之处,本文结合理论分析、选取研究的重要参数、采用控制变量法进行泥石流平衡坡度和平均流速与表面流速之比的室内水槽实验研究,得到以下结论:(1)泥石流屈服应力(τ)、流深(H)和容重(γ)是影响泥石流平衡坡度的重要参数。无量纲化的屈服应力(τ*)包括泥石流的屈服应力、泥石流流深和容重,τ*=τ/(γgH)。屈服应力τ*越大,粘性越大,内部阻力越大,泥石流的平衡坡度越大;反之,屈服应力τ*越小,粘性越小,内部阻力越小,泥石流的平衡坡度越小。(2)泥石流运动沟床粗糙率是影响泥石流平衡坡度的重要参数之一,泥石流运动的底床粗糙率对流动中的泥石流底部产生阻力,泥石流运动的底床粗糙率越大,需要克服泥石流运动的阻力越大,所需要的驱动力越大,所需的平衡坡度也就越大;相反,泥石流运动的底床粗糙率越小,需要克服泥石流运动的阻力越小,所需要的驱动力越小,所需的平衡坡度也就越小。(3)通过控制变量法,实验研究得出泥石流运动的底床粗糙率(n)和无量纲的屈服应力(τ*)与泥石流平衡坡度的关系式为tana=0.0093e18.39n+30τ/(γgH)。(4)泥石流屈服应力(τ)、容重(γ)和流深(H)是泥石流平均流速与表面流速之比的重要参数。无量纲化后的屈服应力(τ*)包括泥石流的屈服应力、容重和流深,τ*=τ/(γgH)。屈服应力τ*越大,粘性越大,内部粘性阻力越大,平均流速与表面流速的比值就越小;反之,屈服应力τ*越小,粘性越小,内部粘性阻力越小,平均流速与表面流速的比值就越大。(5)泥石流运动的底床粗糙率是泥石流平均流速与表面流速之比的重要参数之一。泥石流运动的底床粗糙率越大,阻力越大,对底部速度影响区域越大,平均流速越小,平均流速与表面流速之比也就越小;相反,泥石流运动的底床粗糙率越小,阻力越小,对底部速度影响区域越小,平均流速越大,平均流速与表面流速之比也就越大。(6)通过控制变量法,实验研究得出泥石流运动的底床粗糙率(n)和无量纲的屈服应力(τ*)与泥石流的平均流速与表面流速之比的关系式为Vm/Vs=(17.17n2-3.41n+0.6)[τ/(γgH)]-0.07。
[Abstract]:Debris flow is one of the common geological disasters in the southwest mountainous area, with a sudden movement, fast, powerful, strong impact, destructive, impulse and silt is the main hazard. Equilibrium slope debris flow refers to debris flow in the process of movement, the surface debris flow velocity reaches a fixed value in the ditch in the bed, on the influence of debris flow gully bed for the silt stable state of the slope of the gully bed. Debris flow channel is one of the main means of debris flow control, drainage trough slope drainage is an important indicator of groove design. Design of slope slope balance slot is: when the balance of debris flow slope drainage groove slope is greater than the impact of debris flow, debris flow drainage groove for erosion, will shorten the service life of the drainage groove; when the equilibrium slope drainage groove slope is less than the debris flow, debris flow in the drainage groove within the deposit, not up To the drainage effect. Therefore, the research of debris flow equilibrium slope will play a guiding role in the design of debris flow drainage groove slope. The average velocity of debris flow is one of the most important evaluation and prevention of debris flow parameters. In the field observation, the average velocity of debris flow is difficult to obtain, and the surface velocity is relatively easy to obtain, through both the relationship can be converted into the mean velocity of surface flow velocity. So, it's also important to study on the debris flow average velocity and surface velocity ratio. The previous study on debris flow equilibrium slope and the mean velocity and surface velocity ratio, the affecting factors are mainly concentrated in nature or movement characteristics of debris flow, ignoring the debris flow the influence of debris flow equilibrium slope and mean velocity and surface velocity ratio. The research results are difficult to meet the complex field situation. According to the former research not The shortage of this paper combines the theory analysis, the important parameters selection, the flume experiments were carried out to study the debris flow balance slope and the mean velocity and surface velocity ratio of the control variable method, we get the following conclusions: (1) the debris flow yield stress (tau), flow depth (H) and bulk density (R) is an important influence the parameters of debris flow equilibrium slope. No yield dimensionless stress (t *) including debris flow yield stress, flow depth of debris flow and bulk density, t / R * = (gamma gH). The yield stress is greater the greater the *, viscosity, the greater the internal resistance of debris flow, the greater the degree of balance of slope on the other hand, the yield stress; t * is smaller, the smaller the viscosity, the internal resistance is small, the balance of slope of debris is small. (2) the debris flow gully bed roughness is one of the important parameters of debris flow equilibrium slope, debris flow bed roughness of debris flow in the bottom of the flow resistance, debris flow the 搴曞簥绮楃硻鐜囪秺澶，

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