基于Lu模型的土石坝温度场与饱和—非饱和渗流场耦合分析

发布时间：2018-11-06 08:44

【摘要】：渗流问题一直是土石坝工程研究的重点课题,在实际工程的渗流计算中,渗流场多被单独考虑进行研究,然而,渗流场受外界多方面环境影响,温度作为土石坝渗流场的重要影响因素应加以考虑,土石坝渗流场与温度场是相互影响的双向耦合关系,通过研究两场耦合关系,可以建立更为合理的耦合模型,从而得出较为精确的数值解。由于渗流场与温度场具有较强的耦合关系,可以通过研究温度场来反馈渗流场特性,从而将研究成果应用到渗流监测中,为实际工程提供理论参考。本文主要采用理论分析和数值模拟的方法研究土石坝渗流场与温度场耦合特征。首先,通过理论分析揭示了两场相互作用的机理,在此基础上,利用数值模拟方法分析了两场耦合的基本特征,最后,通过实际工程进一步研究了两场耦合关系。本文主要内容和成果如。下:(1)通过探究多孔介质对流传热基本理论以及相关参数的影响因素,认为土石坝饱和区域传热主要受对流传热影响,非饱和区域主要受热传导影响,也受对流传热影响:同时,认为流体的密度和粘度受温度影响的变化会对土体的渗透性产生影响,尤其是流体粘度的变化会对渗流产生较大影响。(2)研究了 Lu导热模型来描述传热参数随含水率的变化关系。通过实测资料与理论分析研究了 Lu导热模型的计算精度,认为其能够较为精准的刻画土体导热系数随含水率的变化关系。计算结果表明:通过估算岩土体石英含量采用Lu模型来描述导热系数与饱和度的定量关系是可以满足精度要求的;相比于常物性耦合模型,变物性渗流场与温度场耦合模型计算更加精确;渗流场对温度场影响较大,饱和区域温度主要受对流传热影响,非饱和区域主要受热传导影响,渗流速度越大,对流传热影响越明显。(3)以某土石坝工程为例,研究分析了大坝的三维渗流状态,同时,建立了防渗墙渗漏下的土石坝两场耦合模型,分析了渗漏情况下的土石坝温度场与渗流场响应特征,当土石坝防渗墙发生渗漏时,渗漏通道附近的岩土体受库水温影响,必将改变其周围温度场的分布,若通过测温仪器监测到该处温度场的变化,便可以捕捉到渗漏点以及渗漏发生的时间。通过分析大坝温度场变化是可以反馈出大坝渗流场的时空分布特征的。
[Abstract]:Seepage problem has always been a key research topic in earth-rock dam engineering. In the seepage calculation of practical projects, seepage field is mostly considered separately. However, seepage field is affected by many aspects of environment. Temperature as an important factor affecting seepage field of earth-rock dam should be considered. The seepage field and temperature field of earth-rock dam are bidirectional coupling relationship of mutual influence. By studying the coupling relation of two fields, a more reasonable coupling model can be established. Thus, a more accurate numerical solution is obtained. Because of the strong coupling relationship between seepage field and temperature field, the characteristics of seepage field can be feedback by studying temperature field, thus the research results can be applied to seepage monitoring and provide theoretical reference for practical engineering. In this paper, the coupling characteristics of seepage field and temperature field of earth-rock dam are studied by means of theoretical analysis and numerical simulation. Firstly, the mechanism of the interaction between the two fields is revealed by theoretical analysis. On this basis, the basic characteristics of the coupling of the two fields are analyzed by using the numerical simulation method. Finally, the coupling relationship between the two fields is further studied by practical engineering. The main contents and achievements of this paper are as follows. The following conclusions are as follows: (1) by exploring the basic theory of convection heat transfer in porous media and the influencing factors of related parameters, it is considered that the heat transfer in saturated region of earth-rock dam is mainly affected by convection heat transfer, and that in unsaturated region is mainly affected by heat conduction. Also affected by convective heat transfer: at the same time, it is considered that the change of density and viscosity of fluid affected by temperature will affect the permeability of soil. Especially the change of fluid viscosity will have a great impact on the seepage. (2) the Lu heat conduction model is studied to describe the relationship between heat transfer parameters and water content. Based on the measured data and theoretical analysis, the calculation accuracy of Lu thermal conductivity model is studied, and it is considered that it can accurately describe the relationship between soil thermal conductivity and moisture content. The results show that Lu model can be used to describe the quantitative relationship between thermal conductivity and saturation by estimating the quartz content of rock and soil. Compared with the constant physical coupling model, the coupling model of variable physical seepage field and temperature field is more accurate. The influence of seepage field on temperature field is great, the temperature in saturated region is mainly affected by convection heat transfer, and in unsaturated region is mainly affected by heat conduction. The larger the seepage velocity is, the more obvious is the influence of convection heat transfer. (3) taking a certain earth-rockfill dam project as an example, The three dimensional seepage state of the dam is studied and analyzed. At the same time, two coupling models of earth and rock dam under seepage of impervious wall are established, and the response characteristics of temperature field and seepage field of earth and rock dam under seepage condition are analyzed. When seepage occurs in the impervious wall of earth and rock dam, The distribution of the surrounding temperature field will be changed by the influence of the reservoir temperature on the rock and soil near the leakage channel. If the temperature field is monitored by the thermometer, the leakage point and the time of the leakage can be captured. By analyzing the variation of dam temperature field, the temporal and spatial distribution characteristics of dam seepage field can be feedback.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV641

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