岡山大学環境理工学部 Acta Medica Okayama 1341-9099 4 1 1999 In situ determination of field-saturated hydraulic conductivity of subsurface soil of vadose zone by technique of Pressure Infiltrometer 81 92 EN Ichiro Kohno Yuji Takeshita 10.18926/fest/19726 For reducing or bridging gap between small scale laboratory investigations and large scale field investigations, a simple and portable model which is based on real situation and has a compatibility to laboratory core sampling, the pressure infiltrometer technique is introduced for determination of field-saturated hydraulic conductivity. The field -saturated hydraulic conductivity, K(FS), is obtained from measurements of steady flow rates applying constant head as well as falling head principle. The device is also used for field core sampling on which laboratory constant head as well as falling head tests is carried out. The field device is validated through comparison to laboratory core sample experiment and other existing methods. This paper describes first time a versatile field device representing good performance for in situ determination of hydraulic parameters in a short time. No potential conflict of interest relevant to this article was reported.

岡山大学工学部 Acta Medica Okayama 0475-0071 21 1 1986 Determination of Coefficients of Groundwater Flow in Multilayered Aquifers 71 79 EN 10.18926/15835 It is difficult to determine the coefficients of groundwater flow from the data which were obtained from the drawdown test in a multiaquifer system. In this paper, new methods of analyzing drawdown-tests are developed and illustrated with the example to determine aquifer coefficients. In a double-layered aquifer, the analytical solution of drawdown test, in which water is discharged from both layers, is derived. And also the theoretical solution to determine the coefficient of storage by using an index of elasticity of a confined aquifer is derived. From these solutions, methods of determining the coefficient of transmissibility in a double-layered aquifer and the coefficinent of storage in a confined aquifer are got. The example analysis to determine aquifer coefficients is shown. As a result, the characteristics which were obtained by these methods are verified by the real drawdown test data. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 1 1990 Determining Hydraulic Properties of Multilayered Aquifers from Pumping Test Data by Parameter Estimation 99 109 EN Makoto Nishigaki Yuji Takeshita Iichiro Kono 10.18926/15498 In this paper, a numerical procedure of determining hydraulic properties in multilayered aquifers are presented. From pumping test data in multilayered aquifers, the coefficient of permeability and specific storage for each aquifer are determined by using a combination of finite element analysis and nonlinear least-squares optimization technique. This study especially points out necessity of stress-flow coupling analysis to explain the behaviors of pressure head in multilayered aquifer during pumping test. As a example, practical pumping test data were evaluate and the coefficients of permeability and specific storage of aquifers and aquitard were obtained. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 24 1 1989 Determination of Unsaturated Soil Hydraulic Properties by Transient Flow Experiments and Parameter Estimation 107 114 EN Iichiro Kohno Makoto Nishigaki Yuji Takeshita 10.18926/15483 The numerical feasibility of determining soil water retention and hydraulic conductivity functions simultaneously from one-dimensional transient flow experiments in the laboratory by parameter estimation method is evaluated. Soil hydraulic properties are assumed to be represented by van Genuchten's closed-form expressions involving two unknown parameters: coefficients α and n . These parameters are evaluated by nonlinear least-squares fitting of predicted and observed pressure head with time. Gravity drainage experiments are performed for Toyoura standard sand to evaluate the adequacy of this proposed method. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 22 1988 An Experimental Study on Levee Failure Caused by Seepage and Preventive Measures 45 62 EN Iichiro Kohno Makoto Nishigaki Yuji Takeshita 10.18926/15451 There are two classifications of the mechanism of levee failure caused by floods; local seepage failure and progressive failure. The fundamental causes of levee failure produced by piping and erosion were studied and the safety of river leves during floods evaluated in terms of soil machanics. The critical hydraulic gradient and the process of progressive failure were obtained from one- and two- dimensional model experiments for piping and erosion. Problems inherent in and preventive measures against levee failure are discussed. In particular, effects of the Tsukinowa method, the most representative Japanese flood fighting method, were studied experimentally and improvements proposed. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 28 1 1993 Evaluation of closed-form analytical models for predicting unsaturated soil hydraulic properties 61 69 EN Yuji Takeshita Iichiro Kohno 10.18926/15438 Knowledge of the unsaturated soil hydraulic properties is essential requirement for prediction of seepage flow and contaminant transport through the vadose zone. Unfortunately, these parameters are usually time consuming and expensive to measure in the field and laboratory. At the present condition, there are few data accumulation for Japanese soils. In this paper, van Genuchten's closed-form expressions are described to estimate unsaturated soil hydraulic properties. To evaluate the adequacy of these expressions, comparisons are performed between observed and calculated unsaturated hydraulic properties for typical Japanese soils. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 1 1 1996 Parameter Estimation of Unsaturated Soil Hydraulic Properties by Improved Suction Plate Method 115 119 EN Yuji Takeshita Iichiro Kono 10.18926/fest/11619 The unsaturated soil hydraulic properties are essential data to predict the seepage behavior in the vadose zone. In this paper, a new experimental methodology of determining unsaturated soil hydraulic properties is proposed. The soil hydraulic properties are assumed to be represented by van Genuchten's closed-form expressions. Unknown parameters of this model are identified by using a optimization techniques. The optimization approach is nonlinear least-squares algorithm in corporating finite element analysis of one-dimensional nonsteady seepage flow. The advantages of the methods are in the possibility of identifying the optimal unsaturated soil hydraulic properties and diminishing experimental time. To evaluate availability of our proposed method, experimental results which are determined by proposed methods and conventional method are compared for decomposed granite soil. No potential conflict of interest relevant to this article was reported.

岡山大学環境理工学部 Acta Medica Okayama 1341-9099 5 1 2000 Estimation of Unsaturated hydraulic parameters by In-situ technique 71 79 EN Yuji Takeshita Hiroaki Fujii 10.18926/fest/11569 In-situ determination of fundamental hydraulic parameters like variably saturated hydraulic conductivity (K(FS)) and the matric flux potential (Φ(m)) provides a foundation from which several other unsaturated soil parameters can be estimated, namely the Alpha (α*) parameter. This Alpha parameter is the one of the components of 3D unsaturated flow in vadose zone and its value is the measure of the capillary component of unsaturated flow pattern. Here an in-situ technique, Pressure Infiltrometer is introduced to record the steady flow rate applying a constant positive head on an unsaturated soil surface. The aim of this paper is to check the shape factor of 3D flow geometry and to find out its sensitivity on other unsaturated hydraulic parameters and to find out the influence of Alpha parameters on the results of the in-situ estimation of field-saturated hydraulic conductivity. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1990 地盤の浸透特性値の算定方法に関する研究 EN No potential conflict of interest relevant to this article was reported.