JaLCDOI 10.18926/fest/19726
FullText URL 004_081_092.pdf
Author Kohno, Ichiro| Takeshita, Yuji| Mohammad Jafar Ali|
Abstract 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.
Keywords In-situ test Field-saturated Hydraulic conductivity Matric flux potential Wetting front 3D-flow
Publication Title 岡山大学環境理工学部研究報告
Published Date 1999-02-26
Volume volume4
Issue issue1
Start Page 81
End Page 92
ISSN 1341-9099
language 英語
File Version publisher
NAID 120002309012
JaLCDOI 10.18926/15835
FullText URL Mem_Sch_Eng_OU_21_1_71.pdf
Author Takeshita Yuji| Nishigaki Makoto| Kohno Iichiro|
Abstract 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.
Publication Title Memoirs of the School of Engineering, Okayama University
Published Date 1986-11-15
Volume volume21
Issue issue1
Start Page 71
End Page 79
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307954
JaLCDOI 10.18926/15498
FullText URL Mem_Fac_Eng_OU_25_1_99.pdf
Author Nishigaki, Makoto| Takeshita, Yuji| Kono, Iichiro|
Abstract 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.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1990-12-14
Volume volume25
Issue issue1
Start Page 99
End Page 109
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307452
JaLCDOI 10.18926/15483
FullText URL Mem_Fac_Eng_OU_24_1_107.pdf
Author Kohno, Iichiro| Nishigaki, Makoto| Takeshita, Yuji|
Abstract 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.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1989-11-29
Volume volume24
Issue issue1
Start Page 107
End Page 114
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307749
JaLCDOI 10.18926/15451
FullText URL Mem_Fac_Eng_OU_22_45.pdf
Author Kohno, Iichiro| Nishigaki, Makoto| Takeshita, Yuji|
Abstract 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.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1988-03-31
Volume volume22
Start Page 45
End Page 62
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307536
JaLCDOI 10.18926/15438
FullText URL Mem_Fac_Eng_OU_28_1_61.pdf
Author Takeshita, Yuji| Kohno, Iichiro|
Abstract 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.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1993-11-30
Volume volume28
Issue issue1
Start Page 61
End Page 69
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307801
JaLCDOI 10.18926/fest/11619
FullText URL 001_115_119.pdf
Author Takeshita, Yuji| Kono, Iichiro|
Abstract 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.
Keywords unsaturated hydraulic properties back analysis laboratory test groundwater
Publication Title 岡山大学環境理工学部研究報告
Published Date 1996-03
Volume volume1
Issue issue1
Start Page 115
End Page 119
ISSN 1341-9099
language 英語
File Version publisher
NAID 120002313807
JaLCDOI 10.18926/fest/11569
FullText URL 005_071_079.pdf
Author Jafar Ali Mohammad| Takeshita, Yuji| Fujii, Hiroaki|
Abstract 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.
Keywords Field-saturated hydraulic conductivity Matric flux potential Alpha parameter Shape factor In-situ test
Publication Title 岡山大学環境理工学部研究報告
Published Date 2000-02-29
Volume volume5
Issue issue1
Start Page 71
End Page 79
ISSN 1341-9099
language 英語
File Version publisher
NAID 120002313869
Author 竹下 祐二|
Published Date 1990-09-30
Publication Title
Content Type Thesis or Dissertation