土的持水及非饱和渗透特性的宏—微观物理机制研究

发布时间：2018-05-25 11:04

本文选题：非饱和土 + 持水曲线　；参考：《西安理工大学》2017年硕士论文

【摘要】：持水和渗透特性是非饱和土领域的核心问题。文本在回顾前人的基础上,利用已有文献中试验实测值及数值计算,分别对压实黏土的孔径分布演化持水曲线模型、斑脱土滞回持水曲线模型、土的非饱和渗透各向异性、以及黏土颗粒液桥演化规律进行了研究,并得到如下认识:(1)基于典型持水曲线模型对压实黏土提出一种考虑团粒内孔隙和团粒间孔隙的持水曲线模型,从而对压实黏土建立表征团粒结构沿不同水力—力学路径演化的持水曲线模型。利用已有文献中两种压实黏土在不同增、减湿和加载路径下的孔径分布实测数据,标定持水曲线模型中的参数,基于这些实测数据可讨论不同水力—力学路径下与进气值有关参数的演化规律。最后,利用已有文献中这两种黏土压实至不同干密度土样的持水实测数据验证了持水曲线模型在表征压实黏土沿不同水力—力学路径的水力特性以及模拟团粒结构演化过程的有效性。(2)在分析了已有文献中高膨胀性土(MX-80斑脱土)的持水试验结果后,以弹塑性理论和线性各向异性硬化规律为基础,推导出了考虑孔隙比和团粒内孔隙结构变化的滞回持水曲线模型,土样给定压实状态的扫描持水特性可通过考虑不同饱和度阶段的团粒内孔隙比变化规律来表征。最后,利用已有文献中斑脱土试样的滞回持水曲线实测值对受孔隙比和团粒内孔隙结构演化影响的滞回持水曲线以及扫描持水曲线的有效性进行验证。结果表明:所提模型均能够较好的预测斑脱土滞回持水曲线实测值。(3)在Mualem提出的非饱和渗透系数函数的基础上,通过引入孔隙—连通弯曲参数推导出了关于有效饱和度的各向异性系数表达式,同时又根据该表达式将非饱和渗透各向异性划分了9种不同类型,研究其在不同条件下的适用性。利用已有文献中非饱和渗透系数数值试验结果验证了该表达式的有效性。最后,结合Van Genuchten-Mualem函数,利用该表达式定量描述基质吸力对已有文献中5种土的非饱和渗透各向异性的影响。结果表明:该表达式能够描述各向异性系数随基质吸力的变化规律。(4)参考已有文献中粗颗粒模型的简化方法,将黏土颗粒简化为一对相互平行的片状颗粒,且不考虑其表面粗糙度的影响并将其间水分视为液桥。然后,以Yang-Laplace方程为基础,结合黏土颗粒间液桥的几何参数推导出关于无量纲液桥体积与固—液接触角的无量纲液桥毛细力的表达式。令该表达式为零,绘制无量纲液桥体积与固—液接触角的关系曲线,并根据液桥从形成至断裂整个过程将该关系曲线划分为三个区域。最后,整理已有文献中的实测数据,并通过该表达式分析了液桥形成时毛细力与液桥体积和固—液接触角间的关系。
[Abstract]:Water retention and permeability are the core problems in unsaturated soils. On the basis of reviewing the previous studies, using the experimental data and numerical calculation in previous literatures, the evolution of pore size distribution of compacted clay, the model of hysteretic retention curve, and the unsaturated permeability anisotropy of the soil are studied, respectively. And the evolution law of clay particle liquid bridge is studied, and the following understanding is obtained: 1) based on the typical water retention curve model, a water retention curve model is proposed for compacted clay, which takes into account the inner and intergranular pores of the compacted clay. Thus, the water retention curve model of compacted clay is established to characterize the evolution of aggregate structure along different hydraulic and mechanical paths. The parameters of the water-holding curve model are calibrated by using the measured data of pore size distribution of two compacted clay soils under different increasing, dehumidifying and loading paths in previous literatures. Based on these measured data, the evolution law of parameters related to inlet air value under different hydraulic and mechanical paths can be discussed. Finally, Using the measured water retention data of the two clay compacted to different dry density soil samples in the literature, the hydraulic characteristics of the compacted clay along different hydraulic-mechanical paths and the evolution of aggregate structure are verified by the water-holding curve model. The effectiveness of the process. (2) after analyzing the water holding test results of the highly expansive soil MX-80), Based on the elastic-plastic theory and the linear anisotropic hardening law, a hysteretic water retention curve model considering the change of void ratio and pore structure in pellets is derived. The scanning water holdup characteristics of soil samples in given compaction state can be characterized by considering the variation of void ratio in aggregates at different saturation stages. Finally, the effectiveness of the hysteresis water retention curve and the scanning water retention curve affected by the porosity ratio and the evolution of the pore structure in the aggregates are verified by the measured values of the hysteresis water retention curve of the spot soil samples in the previous literature. The results show that the proposed models can be used to predict the measured values of hysteresis water retention curve of spot desoiling soil. The proposed model is based on the unsaturated permeability coefficient function proposed by Mualem. The expression of effective saturation anisotropy coefficient is derived by introducing porosity and connected bending parameters. According to the expression, the unsaturated permeability anisotropy is divided into nine different types. Its applicability under different conditions is studied. The validity of the expression is verified by the numerical results of unsaturated permeability coefficient in the literature. Finally, combined with the Van Genuchten-Mualem function, the effect of matrix suction on unsaturated permeability anisotropy of five soils is quantitatively described. The results show that the expression can describe the variation of anisotropic coefficient with the matrix suction. (4) referring to the simplified method of coarse particle model, the clay particle can be simplified into a pair of parallel flake particles. The effect of surface roughness is not considered and the moisture content is regarded as a liquid bridge. Then, based on the Yang-Laplace equation and the geometric parameters of the liquid bridge between clay particles, an expression for the dimensionless capillary force of the dimensionless liquid bridge with the contact angle between solid and liquid is derived. When the expression is zero, the relation curve between the volume of dimensionless liquid bridge and the solid-liquid contact angle is drawn, and the relationship curve is divided into three regions according to the whole process from the formation of the liquid bridge to the fracture. Finally, the measured data in the previous literatures are collected and the relationship between capillary force and the volume of liquid bridge and the solid-liquid contact angle is analyzed by the expression.
【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】：TU43

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