热流固作用下软土静动力学特性及应用

发布时间：2019-04-19 04:53

【摘要】：近年来,随着核废料填埋、地源热泵、垃圾填埋、热排水固结软基处理等工程技术的兴起,以及大型灾难性爆炸事故产生的高温、高热爆炸产物在岩土体中的传播、扩散及其对地下建构筑物的损伤破坏,使得岩土体中热流固(THM)耦合问题引起广泛的关注,相应的研究也得以迅速发展。由于岩土体热流固耦合效应涉及渗流力学、土(动)力学、传热学等多个学科,影响因素多而复杂,现有研究难以全面、系统地揭示岩土体中热流固耦合作用机理。为此,本文从理论、实验与计算模拟三方面出发对饱和软土在温度影响下的特性变化从固结到动力进行了研究,主要研究内容如下：(1)从Biot固结理论与傅里叶传热理论出发,推导建立了多孔介质热弹性非线性耦合固结方程,并将其退化求解了无限空间中无限长柱形孔洞与有限长圆柱形热源热固结问题,以及各向等压下不排水加热饱和土样热响应问题。在此基础上,分析了各耦合项(水土压缩项、固液相热沉等)与非线性项(热对流)对计算结果的影响。(2)在多孔介质热弹性理论基础上,针对各向等压不排水和排水加热情况,采用弹性、非线性弹性、考虑温度影响的修正剑桥模型,结合温度对水的热膨胀系数的影响,采用COMSOL有限元软件对三轴试样热固结问题进行了求解。同时开展了相应的温控三轴试验,将解析、数值计算结果与试验结果进行了对比分析,讨论了泊松比、弹性模量、水的体膨胀系数等参数对结果的影响。利用COMSOL有限元软件,研究热固结技术在竖井地基加固中的作用机理。在此基础上,建立了热固结本构关系并自主开发了相应的竖井热固结有限元程序TSDSS,弥补了THM耦合理论中采用不考虑温度影响的本构关系无法计算加温排水竖井地基沉降量增大问题,进而通过相应的模型实验,对程序与本构关系进行了验证。(3)对宁波软粘土开展了先固结后不排水加温、先排水加热固结后剪切、先固结再剪切到一定程度变形然后不排水加热、先排水加热固结后不排水动力循环试验四类温控三轴试验,并对试验现象进行了分析,研究了温度对软土的抗剪强度、孔压与变形的影响。其次,在THM耦合理论的基础上,引入考虑温度影响的修正剑桥模型和边界面模型,并在ABAQUS中实现相应的有限元计算方法,对开展的温控三轴试验进行了模拟。(4)基于广义热弹性理论及Biot动力方程,建立了饱和多孔介质热流固耦合动力响应(THMD)控制方程,首先对无限土柱的热动力响应问题进行了求解,并探讨了各因素变化对结果的影响。其次,在COMSOL中建立了无限空间柱形孔洞模型,研究了热流固耦合动力响应(THMD)控制方程中非线性项对计算结果的影响。最后,利用所建立的THMD控制方程,研究了热流固耦合波动问题,探讨各因素对P1波、P2波、T波传播的影响。
[Abstract]:In recent years, with the rise of engineering technologies such as nuclear waste landfill, ground source heat pump, refuse landfill, thermal drainage and consolidation of soft foundation treatment, as well as the high temperature caused by large-scale catastrophic explosion and the propagation of high heat explosion products in rock and soil, Diffusion and its damage to underground structures cause extensive attention to the problem of heat-fluid-solid (THM) coupling in rock and soil, and the corresponding research has been developed rapidly. Because the heat-fluid-solid coupling effect of rock and soil mass involves many disciplines such as seepage mechanics, soil (dynamic) mechanics, heat transfer and so on, the influence factors are many and complex, and the existing research is difficult to reveal systematically the mechanism of heat-fluid-solid coupling in rock and soil mass. Therefore, in this paper, the characteristics of saturated soft soil under the influence of temperature are studied from three aspects: theoretical, experimental and computational simulation, from consolidation to dynamic. The main contents are as follows: (1) based on the Biot consolidation theory and Fourier heat transfer theory, the nonlinear coupled consolidation equations of thermal elasticity in porous media are derived and established. The thermal consolidation problems of infinite cylindrical voids and finite cylindrical heat sources in infinite space and the thermal response of undrained saturated soil samples under isotropic pressure are also solved. On this basis, the effects of coupling terms (soil and water compression term, solid-liquid phase heat sink, etc.) and non-linear term (thermal convection) on the calculation results are analyzed. (2) on the basis of the thermal elasticity theory of porous media, the influence of the coupling terms on the calculation results is analyzed. The modified Cambridge model, which is elastic and nonlinear, considering the effect of temperature on the coefficient of thermal expansion of water, is adopted to solve the problem of non-drainage and drainage heating under isotropic pressure, and the influence of temperature on the coefficient of thermal expansion of water is considered. The COMSOL finite element software was used to solve the thermal consolidation problem of triaxial specimens. At the same time, the corresponding temperature controlled triaxial test was carried out. The analytical and numerical results were compared with the experimental results. The effects of Poisson's ratio, elastic modulus and water expansion coefficient on the results were discussed. By using COMSOL finite element software, the mechanism of thermal consolidation technology in the consolidation of shaft foundation is studied. On the basis of this, the constitutive relation of thermal consolidation is established and the corresponding finite element program TSDSS, for shaft thermal consolidation is developed. It makes up for the problem that it is impossible to calculate the settlement of heated drainage shaft foundation by using the constitutive relation which does not consider the effect of temperature in THM coupling theory, and then through the corresponding model experiment, The program and constitutive relation are verified. (3) the Ningbo soft clay is solidified first and then heated without drainage, then heated and consolidated by drainage and then shear, then deformed to a certain extent and then heated without drainage. Four kinds of temperature controlled triaxial tests were carried out in heating consolidation and undrained dynamic cycle tests, and the effects of temperature on shear strength, pore pressure and deformation of soft soil were studied in this paper, and the effects of temperature on shear strength, pore pressure and deformation of soft soil were studied. Secondly, on the basis of THM coupling theory, the modified Cambridge model and boundary interface model considering temperature effect are introduced, and the corresponding finite element method is implemented in ABAQUS. The temperature-controlled triaxial test was simulated. (4) based on the generalized thermoelasticity theory and Biot dynamic equation, the (THMD) governing equation of thermal-fluid-solid coupling dynamic response for saturated porous media was established. Firstly, the thermal dynamic response of infinite soil columns is solved, and the influence of various factors on the results is discussed. Secondly, the cylindrical cavity model in infinite space is established in COMSOL, and the influence of the nonlinear term in the (THMD) governing equation of heat-fluid-solid coupling dynamic response on the calculated results is studied. Finally, the heat-fluid-solid coupling wave problem is studied by using the established THMD governing equation, and the effects of various factors on the P _ 1 wave, P _ 2 wave and T-wave propagation are discussed.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU447

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