【作者】 陈辉；

【导师】 韦昌富；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2010， 博士

【摘要】 非饱和土水力特性包括土水特征曲线和渗透函数。其中,土水特征曲线描述的是基质吸力与含水量(如：饱和度、体积含水量等)之间的关系；渗透函数描述的是渗透系数与基质吸力或含水量之间的关系。它们在分析有关非饱和土力学行为及污染物地下迁移等问题中起到关键的作用。因此,确定非饱和土水力特性在非饱和土研究及工程实践中具有十分重要的意义。本文围绕非饱和土水力特性的确定问题,开展了测试理论及其方法的研究,具体进行了以下四个方面的工作：1)在利用压力板仪测定非饱和土的土水特征曲线时,常用的取样称量法、溢出水称量法分别存在实测试样质量与实际试样质量不相等、实测排水量与实际排水量不相等问题,从而造成试验结果失真。为此,提出了以溢出水称量法为基础,通过施加修正气压力及校正手段来测量非饱和土水力特性的新方法-溢出水校正称量法。通过取样称量法、溢出水称量法、溢出水校正称量法的对比分析,探讨了它们的适应性。2)针对同一试样的土水特征曲线和水相渗透系数需分开测量及在测量水相渗透系数时采用常水头技术存在的问题,本文介绍了一台能够同时测量非饱和土土水特征曲线和渗透函数的试验装置-非饱和土水力特性联合测试系统,并利用它对两种土样的水力特性进行了测量。通过其测量结果与Tempe仪和VGM模型预测结果的比较,验证了该仪器的适用性。3)基于多孔介质热动力学理论并考虑交界面上各相动态相容条件,建立了一个能描述静态土水特征曲线与动态土水特征曲线间关系的线性粘弹性模型。在此模型的基础上,结合多步流动试验特点,建立了非饱和土的饱和度演化方程,该方程能描述非饱和土流动过程中饱和度的动态变化规律。基于此方程,提出了一种利用非平衡多步流动试验的溢出量试验结果计算非饱和土水力特性的方法,并对该方法的适用性进行了验证。此外,还对该方法应用的相关问题进行了探讨。4)以非饱和土的饱和度演化方程为基础,提出了一种计算试样达到平衡状态所需时间的预估方法,并就时间间隔、容水率及特征时间这几个因素对试样达到平衡状态所需时间的影响进行了研究。更多还原

【Abstract】 The hydraulic properties of unsaturated soils include the soil-water characteristic curve, a relationship between matric suction and water content, and the hydraulic conductivity function, a relationship between hydraulic conductivity and water content or matric suction. These properties play a crucial role in solving the issues related to the unsaturated soils, such as analysis of the mechanical behavior of unsaturated soils, prediction of subsurface flow and transportation, and so on.This research is concerned with the theory and methods that can be effectively applied to determine the unsaturated soil hydraulic properties, and it is summarized as follows:1) In using the pressure plate extractor to measure the soil water characteristic curve, the soil water content is usually determined by weighing the soil sample or weighing the outflow. Due to their intrinsic drawbacks, however, both methods can induce errors in the measurement. To resolve the problem, a new testing method, the adjusted method of weighing outflow, is proposed that can be used to determine the soil water characteristic curve by using the modified air pressure and the adjusted method. By comparing the method of weighing soil and the method of weighing outflow to the adjusted method of weighing outflow, the applicabilities of these three methods are discussed.2) Conventionally, the soil water characteristic curve and the hydraulic conductivity function are not concurrently measured in the same sample, and in measuring the hydraulic conductivity function, the constant head method is usually applied, which is not applicable when the conductivity is very low. To resolve this issue, a combined testing system, which can concurrently measuring the soil-water characteristic curve and hydraulic conductivity function of unsaturated soils, is developed. Comparisons between the testing results using the combined system and those using the conventional methods show that the newly developed testing system works well.3) Based on the theory of multiphase porous media, a linear visco-elastic model is proposed, which can be used to derive the static soil water characteristic curve from the non-equilibrium outflow testing data. Based on this model, a method is proposed to effectively determine the hydraulic properties of unsaturated soils.4) Based on the above model, a novel method is proposed to determine the time for the soil sample to attain the equilibrium. We discuss the effects of the adopted time intervals, the size of suction step, the water capacity and the characteristic time on the equilibrium.更多还原