基于流体力学方法的边坡液化流滑特性研究

发布时间：2018-01-21 08:39

本文关键词： 牛顿流体非牛顿流体 VOF方法液化流滑桩　出处：《江苏大学》2017年硕士论文　论文类型：学位论文

【摘要】：地震后砂土边坡的液化流滑一直是岩土地震工程领域的一个十分重要的课题,也是岩土工程领域的一个研究难点。近些年地震震害结果的调查研究表明,强震作用引起的砂土边坡液化流滑造成的危害不容小觑,砂土边坡的液化流滑机理一直是国内外学者不懈努力的目标。此前,国内外学者大都是从固体力学的角度去研究边坡的液化流滑,也取得了不错的成果。近些年,比较新颖的思路是基于流体力学方法来预测和分析砂土边坡的液化流滑机理,这种思路也更具有工程实际意义。本文首先回顾了近十年典型的地震液化流滑震害,并介绍了部分液化流滑防御措施。然后基于流体力学理论,并运用VOF方法(volume of fluid method,流体体积法)对液化后砂土的流动变形进行了研究,同时也运用VOF方法对液化后砂土进行了流滑推桩效应的研究,最后自主研发了一套测量液化砂土流体特性的试验装置,并进行了相应的试验研究。本文的研究内容包括如下几个方面:(1)回顾了近十年来国内外地震中几种典型的流滑震害,包括地震发生地点以及危害,然后介绍了部分液化流滑的防御措施。(2)基于流体力学理论,利用VOF方法对液化后砂土的流动变形进行了研究。首先将液化后砂土分别视为牛顿流体和幂律型非牛顿流体,建立其流体二维模型,并分析了牛顿流体黏度对其流经定点的速度影响以及非牛顿流体的稠度系数和流动指数对其流经定点的速度影响,并将液化后砂土的工程应变与已有的试验结果进行了简单的对比,验证了本文方法的正确性。然后建立了液化后砂土的三维流体模型,并分别对牛顿流体和非牛顿流体两种情况下流经定点速度的三维结果与二维结果进行了比较,结果发现在误差范围内三维结果与二维结果基本一致。(3)类似地,基于流体力学理论,利用VOF方法对液化后砂土的流滑推桩效应进行了分析。首先,分别建立了单桩模型和液化后砂土的流体模型,通过耦合条件建立了单桩与液化后砂土的流固耦合模型,基于该模型得出了单桩桩身加速度、位移和应力的峰值响应曲线,并据此分析了牛顿流体黏度和非牛顿流体稠度系数和流动指数对桩身加速度、位移和应力峰值响应的影响。然后建立了群桩与液化后砂土的流固耦合模型,与单桩情形类似,分析了牛顿流体的黏度和幂律型非牛顿流体稠度系数和流动指数对桩身加速度、位移和应力峰值响应的影响,所得群桩的结果与单桩情形不同。(4)基于边界层理论,建立了求解液化后砂土黏度的理论公式。然后自主研发了一套测量液化后砂土流体特性的试验装置,并进行了相应的试验研究,得出的结论符合预期结果,从而证明了本装置和公式的适用性,为以后液化后砂土的流体特性研究奠定了试验基础。
[Abstract]:The liquefaction flow slip of sandy slope after earthquake has been a very important subject in the field of geotechnical seismic engineering, and is also a research difficulty in the field of geotechnical engineering. The liquefaction flow slip of sandy slope caused by strong earthquake can not be underestimated. The liquefaction flow slip mechanism of sand slope has been the goal of domestic and foreign scholars' unremitting efforts. Most scholars at home and abroad study the slope liquefaction flow slip from the angle of solid mechanics, and have achieved good results in recent years. The new idea is to predict and analyze the mechanism of liquefaction flow slip of sandy slope based on hydrodynamic method. This idea is also of engineering practical significance. This paper first reviews the typical earthquake liquefaction flow slip damage in recent ten years, and introduces some measures to prevent liquefaction flow slip, and then based on the theory of fluid mechanics. The flow deformation of liquefaction sand was studied by VOF method volume of fluid method (fluid volume method). At the same time, VOF method is used to study the pile-slip effect of liquefaction sand. Finally, a set of experimental device is developed to measure the fluid characteristics of liquefaction sand. The research contents of this paper include the following aspects: 1) reviewing several typical fluid-slip earthquakes in recent ten years, including the location and harm of the earthquake. Then the defense measures of partial liquefaction flow slippage are introduced. 2) based on the theory of fluid mechanics. The flow deformation of liquefaction sand is studied by VOF method. Firstly, the liquefaction sand is regarded as Newtonian fluid and power-law non-Newtonian fluid respectively, and its two-dimensional fluid model is established. The influence of the viscosity of Newtonian fluid on the velocity of flow through a fixed point and the influence of consistency coefficient and flow index of non-Newtonian fluid on the velocity of flow through a fixed point are analyzed. The engineering strain of liquefaction sand is compared with the existing test results, and the correctness of this method is verified. Then, the three-dimensional fluid model of liquefaction sand is established. The results of three-dimensional and two-dimensional velocities of Newtonian fluid and non-Newtonian fluid passing through a fixed point are compared respectively. The results show that in the error range, the three-dimensional results are basically consistent with the two-dimensional results. (3) based on the theory of fluid dynamics, the VOF method is used to analyze the pile-slip effect of sand after liquefaction. The single pile model and the fluid model of the liquefaction sand are established respectively. The fluid-solid coupling model of the single pile and the liquefaction sand is established through the coupling condition. Based on the model, the acceleration of the single pile is obtained. According to the peak response curve of displacement and stress, the pile acceleration is analyzed according to the viscosity of Newtonian fluid, consistency coefficient of non-Newtonian fluid and flow index. Then the fluid-solid coupling model of pile group and liquefaction sand is established, which is similar to that of single pile. The effects of viscosity of Newtonian fluid, consistency coefficient of power-law non-Newtonian fluid and flow index on the peak response of pile acceleration, displacement and stress are analyzed. The results of pile group are different from that of single pile. (4) based on the boundary layer theory, a theoretical formula for solving the viscosity of liquefied sand is established. Then, a set of experimental equipment is developed to measure the fluid characteristics of liquefaction sand. The experimental results are in accordance with the expected results, which proves the applicability of the device and the formula, and establishes the experimental foundation for the later study of the fluid characteristics of the sand after liquefaction.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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