Experimental Study on Determining Unsaturated Property of Soil

This paper deals with the experimental study of hydraulic properties of unsaturated soil. In treating unsaturated zone, a great deal more data are required than are required for the saturated zone, but these properties of soils must be known to apply the finite element approach to actual groundwater flow problems. The purposes of this paper are to propose a rational basis of getting experimental relationships between prossure head() and hydraulic conductivity(K) and between pressure head() and volumetric moisture content(θ) with "the instantaneous profile method" in a laboratory. An apparatus was constructed and test procedures were developed to measure pressure head and volumetric moisture content by using pressure transducers and low-energy gamma ray attenuation. The technique of a low-energy gamma radiation apparatus does provide a means for accurate measurement of water content without disturbing the system into which water is moving. Furthermore rapid measurement of water content becomes possible at any position in a soil so that water content changes with time may easily be followed. The tensiometer~transducer system provides a most valuable means of measuring pressure head with rapid response and with provision of a complete record of the pressure head changes with time

A Consideration on Physics of Saturated-UnsaturatedGroundwater Motion

The purposes of this paper are primarily to research on behavior of groundwater flow in saturated and unsaturated zone, and to present the fundamentals of the theory of groundwater flow. This paper discusses the physics of the saturated-unsaturated groundwater motion. Evaluations confirm the early belief that Darcy's law is of the nature of statistical result giving the empirical equivalent of Navier-Stokes equations. The governing equation of saturated-unsaturated flow in porous media is derived from the law of mass conservation and from the Darcy's law and Richard's equation of motion and is compared with the Klute's diffusion equation which has been widely used in the analysis of unsaturated flow. As a result; it is concluded that the governing equation has the advantage that can be applied for the whole flow region. Typical boundary conditions are enumerated

Analysis of Pump Test Data for Partial Penetrating wells

The solutions of unsteady phreatic flow toward a partially penetrating well in an aquifer of finite thickness are described. Firstly the solution for a confined aquifer is shown. In this case,three methods of analyzing field data with partially penetrating well are given, that is, "Log-Log Method, Log-Log Distance Drawdown Method and Jacob's Method Ajusted for Partial Penetration". By using these methods the hydraulic conductivities and the specific storage of the aquifer may be determined. Secondly the solution for an,unconfined aquifer is shown. In this case, also two methods of analyzing field data with partially penetrating well are given. By using these methods, the anisotropic permeability and the storage coefficient (effective porosity) of the aquifer may be determined. Moreover in each case, the effects of partial penetration are discussed and the limits of adapting the Theis' and Jacob's methods are setted. From these analytic results, some cosiderations are added to determine the anisotropy of permeability and to evaluate the storage coefficient

Transient Flow in Groundwater to Wells in Island Model Aquifer

In order to apply the numerical method to practical groundwater flow problem in the field, the hydraulic properties must be estimated. In this paper, new methods of analyzing drawdown tests were developed and illustrated with some examples to determine hydraulic properties of aquifer. Drawdown tests sometimes have to be performed near the boundary of the aquifer or in the much groundwater supplied aquifer. In such instances, the assumption that the aquifer is of infinite areal extent is no longer valid. Therefore the analytical solutions of unsteady flow due to drawdown test are derived in the conception of "Island Model" that the shape of groundwater level is fixed by the circular water supply which is equilibrium with the pumping rate. By using these solutions, new methods of analyzing drawdown tests which are performed in a confined aquifer and an unconfined aquifer were given respectively and the effect of influence region was evaluated. The example analysis to determine permeability and storage coefficient were shown. As the results,the propriety of the solutions is verified comparing the analytical results with the drawdown test data taken from a real aquifer project

Application of Fininite Element Analysis to Groundwater Flow in Field Problems

The purposes of this paper are primarily to research on behavior of groundwater flow in saturated and unsaturated zone and to develop the most effective methods for solving groundwater flow problems related to civil engineering practice. The mathematical model provides a finite element solution to two- or threedimensional problems involving transient flow in the saturated and unsaturated domains of nonhomogeneous, anisotropic porous media. Before progressing into the various levels of applications the input data and boundary conditions are discussed and evaluated. To demonstrate the flexibility of the finite element approach and its capability in treating complex situations which are often encountered in the field, the groundwater flow through sand bank at flood water levels and the flow through aquifer due to an excavation were analyzed. As the results there were good qualitative agreements between the numerical results and the informations received

Drain System Around the Underground Cavern

In recent years, construction or planning of large-scale underground structures, such as underground power plants, underground oil storage plants and nuclear power plants have been coming into consideration in Japan. To construct such as large-scale underground structures, one of the most important problems is to make clear beforehand the behavior of groundwater around these structures and the other is to carry out proper countermeasure of groundwater, so that these structures can be constructed safely and maintained stability over a long time period. This report describes the results of theoretical studies on the drain systems and at the same time, discusses the drain systems around the underground cavern for the practical underground power stations

Determining Hydraulic Properties of Multilayered Aquifers from Pumping Test Data by Parameter Estimation

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