Research on the Method of Determining Unsaturated Soil Hydraulic Properties by In-Situ or Laboratory Tests

非饱和土壤水力特性的知识是一个基本的要求，通过包气带的流量和污染物输运预测。然而，非饱和土壤水力学特性的获得是困难的。由于确定非饱和土壤水力特性的方法尚未建立，日本土壤的数据积累较少。本研究探讨了确定非饱和土壤水力特性的新方法。本研究取得的主要成果如下：1.提出了一种利用室内pF试验或现场抽水试验资料估算非饱和土水力特性的新方法。该方法采用非线性最小二乘算法，结合非稳定饱和-非饱和渗流有限元分析。该方法的优点在于可以确定最佳的非饱和土壤水力特性，并缩短试验时间.土壤水分 ...更多信息 假设LIC特性由涉及五个未知参数的货车van Schlichten的封闭形式表达式表示。这些未知参数允许液压功能的形状具有很大的灵活性。因此，当这些函数确定后，可以避免在非饱和水流模型中对非饱和土壤水力特性数据的繁琐处理.本文提出的抽水试验数据处理方法，适用于室内试验中采用假定的潜水含水层模型所测得的抽水试验数据实例。预测的饱和导水率和非饱和土壤水力特性进行了比较独立确定的水力特性相同的土壤。良好的协议被发现。4.通过pF试验中的压头数据判断重力泄流的平衡状态。含水量与时间的测量被用来估计三个未知系数的货车vanivhten的表达式。本程序适用于丰浦砂和风化花岗岩土。少

Knowledge of unsaturated soil hydraulic properties is an essential requirement for prediction of flow and contaminant transport through the vadose zone. It is, however, difficult to obtain unsaturated soil hydraulic properties. Because the method of determining unsaturated soil hydraulic properties is not yet established and there are few data accumulation for Japanese soils. In this research, some new methods to determine unsaturated soil hydraulic properties are investigated. The results obtained in this research are as follows :1. A new method of estimating unsaturated soil hydraulic properties from pF tests in the laboratory or in-situ pumping test data is proposed. In this method a nonlinear least squares algorithm incorporating finite element analysis of non-steady saturated-unsaturated seepage flow is used. The advantages of the proposed method are in the possibility of identifying the optimal unsaturated soil hydraulic properties and diminishing experimental time.2. Soil hydrau … More lic properties are assumed to be represented by van Genuchten's closed-form expressions involving five unknown parameters. These unknown parameters allow great flexibility in the shaped of the hydraulic functions. Therefore when these functions are determined, the cumbersome handling of unsaturated soil hydraulic properties data in models of unsaturated flow can be avoided.3. The proposed method for pumping test data is applicable to the examples of pumping test data which are measured by a hypothetical unconfined aquifer model in the laboratory experiments. Predicted the saturated conductivity and unsaturated soil hydraulic properties are compared with independently determined hydraulic properties for the same soil. Good agreement is found.4. Pressure head data in pF test are measured to judge the equilibrium state of the gravity drainage. Water content versus time measurements are used to estimate three unknown coefficients in the van Genuvhten's expressions. This procedure is applied to Toyoura sand and decomposed granite soil. Less