基于水气二相流的土水特性测试方法研究

发布时间：2018-11-18 17:39

【摘要】：土孔隙中不仅有液相的流动，也有气相的流动。非饱和土的土水特性，表征了非饱和土中基质吸力以及水、气渗透性与含水量的相关关系，包括土水特征曲线和相对渗透率曲线。土水特性是解释非饱和土行为和求解水气运动的基本本构关系，是构筑非饱和土中各种重要关系的基础。传统测试土水特性的方法大都未能考虑土孔隙中气相的作用，而且土水特性三条曲线的测定往往是分开进行的，难以保证三个本构关系的相容性。本文基于水气二相流的基本理论，开展了非饱和土水特性的测试理论和方法的研究，开展的主要研究如下： 1）基于土中水气二相流的基本理论，提出一种新的非饱和土水特性测试方法。测试方法包含数值反算部分和测试试验部分，能反映非饱和土中水、气相互作用特征，同时得到土样的土水特征曲线和水、气相相对渗透率曲线，保证了三条本构关系的相容性。 2）发展了一种水气二相流耦合求解与区间逼近相结合的土水特性反算方法。反算方法找到了合适的水气二相流解耦路径和参数优化路径，能够结合特定的土水特性数学模型反算得到土样的非饱和土水特性。编写了相关计算程序，通过干过程和湿过程的模拟，验证了反算程序的正确性、收敛性及数值稳定性。 3）自主设计了一个干湿循环多步流动试验系统。试验系统能够模拟土样中水气耦合运动，能够根据土样中水流动状态自动施加干湿循环条件，实时采集试样边界条件和溢出水总量，为土水特性数值反算提供了数据支撑。 4）验证了测试方法的正确性和适用性。根据实时采集试样溢出水流量和边界条件、初始条件，结合相应的数值反算程序，同时得到了试样非饱和土水特征曲线和水、气相相对渗透率函数曲线。将测试所得的非饱和土水特性作为已知条件，进行水气二相流耦合求解，对比分析计算的溢出水量与试验采集溢出水量以及水分运移规律，，验证了测试方法的正确性。
[Abstract]:There is not only liquid flow in soil pores, but also gas phase flow. The soil-water properties of unsaturated soils are characterized by the relationship between the matrix suction, water and gas permeability and water content, including soil water characteristic curve and relative permeability curve. The soil-water characteristic is the basic constitutive relation to explain the behavior of unsaturated soil and to solve the water vapor motion. It is the foundation of constructing various important relations in unsaturated soil. Most of the traditional methods for measuring soil-water properties fail to consider the effect of gas phase in soil pores, and the determination of three curves of soil-water characteristics is often carried out separately, so it is difficult to ensure the compatibility of the three constitutive relations. Based on the basic theory of water and gas two-phase flow, the testing theory and method of unsaturated soil-water characteristics are studied in this paper. The main research results are as follows: 1) based on the basic theory of water-gas two-phase flow in soil, A new testing method for unsaturated soil and water characteristics is presented. The test method includes numerical backcalculation part and test section, which can reflect the interaction characteristics of water and gas in unsaturated soil. At the same time, the soil-water characteristic curve and the relative permeability curve of water and gas phase of soil sample are obtained. The compatibility of the three constitutive relations is guaranteed. 2) an inverse calculation method of soil and water characteristics is developed, which combines the coupling solution of water and gas two-phase flow with interval approximation. An appropriate decoupling path and parameter optimization path are found by the inverse calculation method, and the unsaturated soil-water characteristics of soil samples can be obtained by combining with a specific mathematical model of soil-water characteristics. Through the simulation of dry and wet processes, the correctness, convergence and numerical stability of the inverse program are verified. 3) A dry and wet cycle multi-step flow test system is designed. The test system can simulate the coupled motion of water and air in soil sample, can automatically apply dry and wet circulation conditions according to the flow state of water in soil sample, and collect the sample boundary condition and the total amount of overflow water in real time, which provides the data support for the numerical inverse calculation of soil water characteristics. 4) the correctness and applicability of the test method are verified. According to the overflow water flow and boundary conditions, initial conditions and the corresponding numerical inverse calculation program, the characteristic curves of unsaturated soil and the relative permeability function curves of water and gas phase are obtained at the same time. Taking the unsaturated soil-water characteristic of the test as the known condition, the coupling solution of water-gas two-phase flow is carried out, and the correctness of the test method is verified by comparing the calculated overflow water with the experimental collected overflow water and the water migration law.
【学位授予单位】：三峡大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411

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