导截流工程中的几个随机性问题的研究

发布时间：2019-07-08 12:27

【摘要】：本文以随机性为大的研究背景和研究主题,针对施工导截流过程中的三个由随机性所引发的工程问题,在分析了各问题自身特点的基础上,分别应用了三种不同的随机性分析方法,使各问题从与以往不同的角度得到了新的认识和一定程度上的解决。具体地,本文所分析的三个随机性问题分别为：A.受水文和水力随机性共同影响时的导流风险分析问题；B.由水流脉动随机性以及块体在床面所处位置随机性所产生的,截流块体的随机性起动问题；C.在脉动水压作用下的闸门的随机振动问题。对以上三个问题的研究,分别构成了本论文的第三、四、五章。 1)对于随机性问题A,本文应用了一种概率密度演化的方法,以达到“既能对受多重随机因素影响时的风险演化过程进行分析,又能获取最终的导流风险率”的研究目的。鉴于上游围堰的堰前水位能综合地体现出水文和水力随机性的共同影响,因此,本文以堰前水位作为导流风险的载体,试图采用概率密度演化方法对堰前水位分布在各时刻的概率密度进行求解,以期能据此对导流风险的演化过程进行分析。为此,在第三章中,基于概率密度演化方法的研究思路,首先根据水库蓄量平衡关系,为该方法的应用提供了一个关于堰前水位的状态方程。然后,在分析了水文和水力不确定性的基础上,通过对各随机参数进行以设计值为均值的正态分布假设,向状态方程中引入了水文和水力随机性。根据此状态方程,本章随后建立了针对堰前水位的广义概率密度演化方程,并介绍了基于此方程的对堰前水位分布的概率密度进行求解的计算流程。同时,通过在该计算流程中添加吸收壁边界条件,提出了导流风险率的计算方法。本章最后,以某水电工程为例,通过数值求解带有7个随机变量的广义概率密度演化方程,成功地获取了3个典型流量水平下的堰前水位分布在计算时段内各时刻的概率密度,并对各流量水平下的导流风险率进行了计算,为了对比验证,该风险率还与由Monte-Carlo法所得到的风险率进行了比较。通过以上对实例的分析,可以发现,应用概率密度演化方法能够方便地获取由传统方法所不易得到的堰前水位分布的概率密度及其随时间的变化情况,可以直观、实时地从蕴含有丰富概率信息的该变化过程中,对导流风险进行分析与判断。另外,通过与Monte-Carlo法的计算结果进行对比,说明了基于概率密度演化方法还可以对导流风险率进行有效的求取。 2)对于随机性问题B,本文根据对块体随机性起动现象的一种描述,应用Monte-Carlo法,对处于多种情况下的截流块体的起动概率进行了计算。具体地,在第四章中,首先仅以瞬时流速作为随机参数,对处于无阻挡无遮掩这一简单情况下的截流块体的起动概率用Monte-Carlo法进行了计算,并通过与该情况下的理论解进行对比,说明了Monte-Carlo法在计算块体起动概率方面的可行性。然后,对块体处于更复杂、受更多随机性因素影响下的情况,仍用Monte-Carlo法计算了其起动概率。此处,这些情况包括：有阻挡无遮掩以及有阻挡有遮掩的情况。另外,为能更加合理地反映出截流块体的实际起动情况,本章还首次应用Monte-Carlo法对块体在三维空间内的起动概率进行了计算,得到了块体在该情况下的一些起动规律,并与在二维情况下的相同计算进行了比较。通过以上的一系列计算,显示了Monte-Carlo法可以方便且有效地求取受多重随机性因素影响的截流块体的起动概率,使截流块体在动水作用下的起动难度(或稳定性)可以从概率的层面上进行量化,为截流块体的选取及其带来的相关的风险估计提供了依据。 3)对于随机性问题C,本文应用正交展开的方法,使脉动水压从频域内的随机过程转化为时域内的随机过程,从而为由脉动水压所引起的闸门振动问题建立了激励模型。通过与目标随机过程在均值、方差以及功率谱层面的比较,验证了该激励模型的准确性。进一步地,本章以一个简单的平板结构作为闸门受力体,将由激励模型所生成的252条激励样本作用于该结构,并通过概率密度演化方法对该结构进行了动力响应分析,得到了结构任意位置处的振动位移量在计算时段内任意时刻的概率分布情况,为闸门振动研究提供了一种“频域到时域的激励建模——概率密度演化方法的响应分析”的研究模式。
[Abstract]:Based on the analysis of the characteristics of each problem, three different stochastic analysis methods are applied to the research background and the research topic of the randomness, and based on the analysis of the characteristics of each problem, So that the problems can be solved in a new way and a certain degree from the angle different from that of the past. In particular, the three stochastic problems analyzed in this paper are: A. The problem of the analysis of diversion risk in the case of the mutual influence of the hydrological and hydraulic randomness; B. the randomness of the flow pulsation and the randomness of the block in the position of the bed surface, and the random starting of the shut-off block; C. The random vibration of the gate under the action of pulsating water pressure. The third, fourth and fifth chapters of this thesis are respectively formed in the research of the above three problems. 1) For the problem of randomness A, a method of probability density evolution is applied in this paper to reach the aim of the "The risk evolution process of multiple random factors can be analyzed, and the final diversion risk rate can be obtained.". In view of the fact that the pre-weir water level of the upstream cofferdam can comprehensively reflect the mutual influence of the hydrological and hydraulic randomness, this paper, taking the pre-weir water level as the carrier of the diversion risk, tries to adopt the probability density evolution method to the probability density of the pre-weir water level distribution at all times. The line is solved with a view to the evolution of the diversion risk accordingly. To this end, in the third chapter, based on the research thinking of the method of probability density evolution, firstly, according to the reservoir volume balance relationship, a shape of the water level before the weir is provided for the application of the method. Then, on the basis of the analysis of the hydrological and hydraulic uncertainties, the hydrologic and hydraulic power is introduced into the state equation by assuming a normal distribution hypothesis with a mean value of the design value for each random parameter. In this chapter, the generalized probability density evolution equation for the water level of the weir is set up in this chapter, and the probability density of the water level distribution before the weir is calculated based on the equation. in addition, by adding that boundary condition of the absorption wall in the calculation flow, the invention provides a flow-guide risk ratio meter, In the end of this chapter, a general probability density evolution equation with 7 random variables is solved by means of a numerical solution, and the general probability density evolution equation with 7 random variables is solved by numerical solution. The rate density is calculated and the risk rate of the flow at each flow level is calculated. In order to compare the verification, the risk ratio is also compared with the risk rate obtained by the Monte-Carlo method. By the analysis of the above examples, it can be found that the probability density of the pre-weir water level distribution which is not easily obtained by the conventional method and the change of the time with time can be conveniently obtained by using the probability density evolution method. and the diversion risk can be intuitively and real-time from the change process containing abundant probability information, In addition, by comparing with the calculation results of the Monte-Carlo method, the probability density evolution method can also be used to carry out the flow-diversion risk rate. In this paper, based on the description of the random starting phenomenon of the block, the method of Monte-Carlo method is applied to the start-up of the shut-off block in many cases. The probability is calculated. In the fourth chapter, only the instantaneous flow rate is used as the random parameter, the start-up probability of the shut-off block under the simple condition without blocking is calculated by the Monte-Carlo method, The theoretical solution is compared, and the Monte-Carlo method is used to calculate the block. The feasibility of the dynamic probability. Then, the block is in a more complex and more random factor, and the Monte-Carlo method is still used. The start-up probability is calculated by the method. Here, these conditions include: In addition, the start-up probability of the block in three-dimensional space is calculated by using the Monte-Carlo method for the first time in order to more reasonably reflect the actual start-up of the block. some of the starting laws of the state, and in the two-dimensional case Through the above series of calculations, it is shown that the Monte-Carlo method can conveniently and effectively obtain the starting probability of the shut-off block affected by the multiple random factors, so that the starting difficulty (or stability) of the shut-off block under the action of moving water can Quantization from the level of probability, the selection of the closure block and the phase brought by it In this paper, the stochastic process of the pulsating water pressure from the frequency domain to the random process in the time domain is applied to the stochastic problem C, which is caused by the pulsating water pressure. The excitation model is established by the vibration of the gate. By comparison with the mean, variance and power spectral level of the target stochastic process, Further, this chapter uses a simple plate structure as the force body of the gate, and the 252 excitation samples generated by the excitation model act on the structure, and the probability density evolution method In this paper, the dynamic response analysis of the structure is carried out, and the probability distribution of the vibration displacement in any position of the structure at any time in the calculation period is obtained, and a kind of "The Response Analysis of the Method for the Modeling of the Frequency Domain to the Time Doai" is provided for the gate vibration research.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV551

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