【作者】 张雪东；

【导师】 赵成刚；

【作者基本信息】 北京交通大学 ， 防灾减灾及防护工程， 2010， 博士

【摘要】 摘要：土水特征曲线(Soil-Water Characteristic Curve,简称SWCC)是非饱和土力学中描述土的非饱和状态对其水力、力学特性影响的一个重要工具,它在“含水量-吸力”空间中的位置和形状能够反映土中孔隙结构的特点(孔隙的大小和分布规律)以及土的持水能力；非饱和土力学中的许多研究领域,如强度理论、渗流理论、固结理论、本构理论都涉及到SWCC的应用；由于SWCC的量测成本高、周期长、难度大,且试验数据处理和分析也远比饱和土更加复杂,这在一定程度上导致了非饱和土力学的实践和应用还远远地落后于理论研究。为了使非饱和土力学理论能够方便地应用于工程实践,本文围绕SWCC在工程应用中存在的问题,开展了一系列的研究,主要包括以下几方面的工作：(1)根据SWCC试验散点,拟合得到能够正确地反映土中孔隙结构特点和持水能力的函数,是SWCC应用的基础和前提。本文在分析了SWCC应用的基本步骤、SWCC形状特点的基础上,结合现有SWCC模型的函数形式的特点,分析了拟合SWCC试验散点时可能出现的问题,而后在统计了21种土的SWCC拟合结果的基础上,首次提出了一种使用不完整SWCC(测量未到达残余状态)的试验点,拟合得到能够正确地反映土中孔隙结构特点和持水能力的函数的计算方法,使用这种方法,可以解决在试验条件有限,无法测得完整SWCC时,难以根据试验结果准确地确定一些非饱和土力学模型中的相关参数的取值问题。(2)以概率论为基础,利用SWCC和孔隙(水)分布函数之间的关系,提出了平均孔隙半径的概念,而后以此为基础得到了一个能够模拟变形对SWCC影响规律的计算模型；由于该模型考虑了土中的初始孔隙结构对SWCC随变形的变化规律的影响,所以它能够给出比较理想的计算结果；该模型可为建立分析非饱和土的水力、力学特性相互影响的计算模型奠定基础。(3)以概率论为基础,提出了一个能够考虑土中孔隙结构影响的饱和土渗透系数计算模型,而后结合本文提出的模拟SWCC随变形的变化规律的计算模型,以及Mualem(1976)相对渗透系数模型,建立了一个能够模拟变形对非饱和土渗透系数影响的计算模型,该模型不仅能够考虑孔隙大小的变化对渗透系数的影响,更能够考虑孔隙结构变化的影响,这使得预测结果能够更加接近于实际情况。(4)以传统域模型的基本原理为出发点,提出了一个能够方便地模拟多次浸润(吸湿)、干燥(脱湿)过程,以及在含水量(吸力)变化历史未知的情况下模拟含水量随吸力变化规律的SWCC滞后模型；而后以该模型为基础,得到了一个利用边界干燥曲线以及一条一阶浸润扫描线预测边界浸润曲线的计算方法,使用该方法,可以减少SWCC滞后模型计算时所需实测的数据,从而使现有的一些SWCC滞后模型能够方便地应用于实际工程中。更多还原

【Abstract】 Soil-Water Characteristic Curve(short for SWCC) is an effective tool for describing the influence of unsaturated state on the hydraulic & mechanical behavior in unsaturated soil mechanics; the pore size distribution characteristic, as well as the water retention capacity of a soil sample, can be estimated through the position and shape of a SWCC in the ’water content-suction’ space; in unsaturated soil mechanics, many research fields, such as the strength theory, seepage theory, consolidation theory and constitutive theory, use SWCC to reflect the influence of water content on the mechanical and hydraulic behavior of soil; Measruing SWCC is costly and time consuming, and the way of how to analyze and interpret the experimental data are far more difficult than that in saturated soil mechanics, which may become one of the reasons that prevent the unsaturated soil mechanics theory to be implemented in the engineering practice, to solve this problem, the following research work on SWCC has been carried out in this dissertation.(1) SWCC is usually used for estimating the parameters needed in the numerical calculation in unsaturated soil mechanics, by analyzing the characteristic of the existing SWCC models as well as the shape of SWCC, the aspects that need to be taken into account when determining the related parameters by using measured SWCC data have been discussed, after that, on the basis of the statistical results of 21 kinds of soils, a method that is able to estimate the parameters needed in the numerical calculation in the case that the measured SWCC data has not reached the residual state, has been proposed in this dissertation, with the help of this method, the use of SWCC in the engineering practice can become more convenient to some extent.(2) Based on the theory of probability, together with the relationship between SWCC and the pore water distribution function, a variable called the average pore size radius, which can characterize the pore size of a soil sample, is defined in this paper, and on the basis of this concept, a method for modeling the variation law of SWCC with soil deformation is then proposed. in this method, two measured SWCCs with known porosity is needed for calibrating the parameters, besides, the influence of the initial structure of a soil sample on the variation law of SWCC with deformation could also be taken into account in this method. (3) Based on the theory of probability, a saturated permeability function, which could take the influence of soil structure into account, has been proposed in this paper; combined with the Mualem(1976) relative permeability function model, together with the variation law of the structural parameters during deformation proposed in this dissertation, the influence of deformation on unsaturated permeability function was modeled, which can ensure the calculation results become more close to the practical situation.(4) Taking the fundamental theory of traditional domain model as the starting point, a simple model, which is able to simulate the hysteretic characteristic of a SWCC under arbitary drying and wetting paths, as well as predict the scanning curves in the case when the water content(or suction) variation history is unknown, is proposed in this dissertation; then, based on the proposed model, a method that is capable to predict the boundary wetting curve with the help of a measured boundary drying curve together with a first-order wetting scanning curve is presented, by using this method, the amount of the experiment data nessceary for calibrating the parameters in the hysteresis models could be reduced, which can make the hysteresis models more conveniently used in the engineering practice.更多还原