【作者】 刘丽；

【导师】 陈洪凯；

【作者基本信息】 重庆交通大学 ， 港口、海岸及近海工程， 2011， 博士

【摘要】 泥石流爆发突然,冲击破坏力强,是我国主要的公路水毁类型。而水石流是主要的泥石流灾害类型之一,在我国分布广泛,发育典型,灾害严重。本文主要针对水石流的冲击破坏特征,以研究水石流的液冲击为主,分析其对公路桥涵等防护构筑物的破坏机理,对沟道地形的变形特性演变机理。通过理论分析及试验研究,以随机过程分析、运动流体力学、随机信号分析理论、概率论与数理统计、应用统计学、泥石流运动力学等多方面学科交叉来分析研究水石流的瞬时流谱,瞬时加速度谱及瞬时脉动压力谱以及与沟道地形的相互作用关系。主要研究内容及创新成果如下：第一、将随机过程理论应用到水石流中,证明水石流液相瞬时流速具有可测性,同时满足平稳随机过程,具有遍历性及各态历经性。第二、根据水石流模型槽实验,实时量测水石流液相流体的瞬时流速沿断面水深分布,分析水石流液相流体断面平均紊动强度沿水深分布,证实近底部分紊动强烈,同时证明液相流速的信号为低频的或比较平稳的信号,频率一般在20HZ以内,能量主要在1OHZ范围内。而稳定频带主要集中在1HZ以内,说明流速信号在1HZ内信号集中。第三、根据测定的水石流液相流体瞬时流速信号,应用随机过程理论,建立水石流液相流体质点瞬时流速信号随机概率模型。选定测试的60组实验信号进行模拟分析,对其进行时频域转换,分析其振幅、圆频率及随机初相位角的概率分布,找出其给自的伪随机数发生器,模拟信号的构建主要由基波与多次谐波随机组成,并创建了频幅权重系数的构建原则,建立等价的模拟判定准则,模拟信号与原信号的统计特征值及谱密度函数吻合较好。第四、基于水石流液相随机质点流的流速概率模型的各种分析,通过对试验数据的多次计算和数据拟合,推导得到了水石流液相随机质点流的加速度概率模型,随机质点脉动压力的概率模型。并通过其逆过程已知脉动压力谱推导脉动流速谱,验证其推导模拟过程精确可靠。第五、根据推求的脉动压力谱,利用权法,计算出脉动压力的横向分布规律,并与地形等值线对比发现,流速大,脉动压力大,其断面冲刷深度则大,沟槽变化幅度增大。第六、分析了水石流对桥涵墩台冲击破坏机理,水石流液相对基础的冲刷逐步加大,冲刷深度超过基础埋深,基底承载力逐渐降低,导致桥墩失稳；另外由于水石流强大的冲击力,导致墩台的抗倾覆能力逐渐减弱。第七、利用随机质点瞬时流谱至脉动压力谱的转换关系,通过丁坝实测冲刷地形数据与脉动压力信号进行对比发现：脉动压力等值线发育规律与冲刷地形变化走势基本一致,同时,水流冲击力变幅与脉动压力变幅相差较大,分析原因并构建了随机流与物体作用时的能量方程,为后续的流固耦合研究打下坚实基础。更多还原

【Abstract】 Characterized by sudden outbreak and strong destructive power, the debris flow is the main type of water damage of highway. As one of the main debris flows, water-rock flow has the feature of wide distribution, fast formation and serious destruction. Based on the failure characteristics of water-rock flow and liquid rock impact of water-rock flow, the dissertation tries to explore into the negative influence of water-rock flow on highway, bridge and culverts and its impact on deformation characteristics of channel topography. Through theoretical analysis and experimental studies, the relationship among instantaneous flow spectrum, instantaneous acceleration spectrum, fluctuation pressure spectrum and channel topography has been studies based on interdisciplinary research such as fractal stochastic process, fluid dynamics, stochastic analysis theory, probability theory and mathematical statistics, applied statistics and mechanics of debris flow transport. The main contents and innovation achievements are as follows:First, after applying random process theory into water-rock flow, it has been demonstrated that instantaneous velocity of water-rock flow liquid can be measured; meanwhile, it can satisfy stable random process and is characterized by ergodicity.Second, based on water-flow model experiment, distribution of instantaneous velocity of water-rock flow liquid along the section of water depth has been obtained; the relationship between average turbulence intensity of water-rock flow liquid section and water depth has been analyzed; strong turbulence intensity has been verified; the signal of the liquid velocity is low in frequency or stable with the frequency within20HZ and intensity within10HZ. If the frequency band is within1HZ, the velocity signal is within1HZ.Third, on the basis of instantaneous velocity signal of water-rock flow liquid, random probability model of instantaneous velocity signal of water-rock flow liquid has been established with random process theory. Simulation analysis has been conducted to60group experiment signals; based on time-frequency transformation, analysis of amplitude, circular frequency and distribution of random phase angle probability, establishment principle of weight coefficient and equivalent simulated determination principle have been built; statistic eigenvalues and of spectral density function simulation signals and those of original signals are identical.Fourth, according to analysis of velocity probability model of water-rock flow liquid random particle, acceleration probability model of water-rock flow liquid particle and probability model of random particle fluctuation pressure have been established after constant computation and data fitting; fluctuation velocity spectrum obtained from known fluctuation pressure spectrum by inverse process has verified the accuracy and reliability of deduction and simulation process.Fifth, according to fluctuation pressure spectrum, lateral distribution law of fluctuation pressure has been obtained by entropy method; compared with topography isopleth, it has been found that if water-rock flow has fast velocity and large fluctuation pressure, there will be deep section scouring and larger groove variation.Sixth, the influence of water-rock flow on bridges and piers has been analyzed; increasing scouring, deeper scouring and decreasing load of base will lead to unsteadiness of piers; besides, strong force of impact will result in weaker overturning resistance property of piers.Seventh, on the basis of transformation relationship between random particle instantaneous flow pattern and fluctuation pressure spectrum, it has been found after comparing groyne measured topography data and fluctuation pressure signals: development rule of fluctuation pressure isopleth tallies with scouring topography variation; meanwhile, after analyzing the difference between variation of force of impact of water and fluctuation pressure variation, energy equation of random flow has been established which lays a solid foundation for the following study of fluid-structure interaction.更多还原