Study on Measuring System of Subsurface Contamination using Complex Dielectric Method

For evaluating subsurface contamination, sampling method (boring) is commonly used, but this method cannot monitor the change of in-situ contamination and concentration with respect to time. The purpose of this study is to develop a measuring system for subsurface contamination in which a so-called FDR-V system (Frequency Domain Reflectometry with Vector network analyzer) was employed to measure the salinity contaminant. This FDR-V method is a coaxial probe method,which allows the measurement of the complex dielectric constant from 1GHz to 18GHz. The experimental study indicates the possibility in measuring both the salinity concentration and volumetric moisture content

The Hydrogeological Setting of Ghana and the Potential for Underground Dams

Increasing human population, changing lifestyles and environmental considerations have resulted in increased utilization of groundwater resources worldwide. Thus, in turn, has led to the decline of groundwater levels in some countries and Ghana is no exception to this problem. To augment the availability of groundwater resources for various uses, numerous techniques have been developed in many part of the world, one of which is the construction of underground dams. The successful construction and utilization of underground dams, however, depends very much on the physical and hydrogeological conditions at the dam sites. Ghana is underlain by Precambrian crystalline igneous and metamorphic rocks ; and Paleozoic consolidated sedimentary formations. There are further subdivided and described locally as the Birimian, Dahomeyan, Buem, Togo Series, Tarkwaian, Granites, Voltain, Coastal Block Fault, Coastal Plain and Quaternary Alluvium. The review of these and the pre-requisite conditions necessary for the construction of underground dams indicate that underground dams could be constructed and utilized in some parts of Ghana, especially where the overburden is shallow, in the Dahomeyan granites and in the recent formations consisting of alluvial and coastal sands and gravels. This paper is part of a continuing research programme being carried out by the authors

Measuring Method of Water Content for High compacted Bentonite Block by using Frequency Domain Reflectometry

In the high-level radioactive waste disposal project, in order to know the infiltration behavior, it have to be examined that the bentonite buffer material is used as a barrier, and the measuring device of moisture with the high accuracy is required. In this study it is discussed the usefulness for Frequency Domain Refrectometry (FDR) method through the measuring dielectric constant and making the calibration curve for the several kinds of bentonite material block (pure and silica sand mixing)

Floods in Bangladesh: A Comparative Hydrological Investigation on Two Catastrophic Events

Flood becomes regular feature in riverrine Bangladesh. Every year, around 21 percent of land is flooded during monsoon season, however, in severe situation this figure shot up to more than 60 percent of total land. This paper is an attempt to analyze hydrological characteristics of two catastrophic events (1988 and 1998 flood) in the light of flood history in Bangladesh. The analysis demonstrates that the 1998 flood was more severe than the 1988 one. Moreover, the 1998 flood was also prolonged than the 1988 flood due to heavy rainfall inside and outside of the country. Finally, flood management issues in Bangladesh have been analyzed and found that structural solution to mitigate flood is not the only solution. Based on the analysis some possible mitigation options are put foward

DEM based Flood Extent Delineation in Dhaka City, Bangladesh

Dhaka city, the capital of Bangladesh and home for more than 10 million people, has been affected by seasonal flooding almost in every year, however, the situation aggravates depending on rainfall and surrounding river waters. The aim of this paper is to delineate the flood extent in Dhaka city using digital elevation model (DEM), an integral part of geographic information system. Catastrophic floods of the 1988 and 1998 events are taken into consideration. Hydro-meteorological assessment of these events revealed that the 1988 flood was severe due to the lack of flood protection in the city together with transboundary flow of the major rivers while the 1998 flood was become deluge due to incessant monsoonal downpour along with early peaked of the river water levels. The 1998 event has done colossal damage in the city compare to the 1988 event. Flood extent estimation showed that DEM data is very precious to model inundation in the city, however, in order to be spatially explicit flood model, high resolution DEM is necessary. Finally, flood management issues are reviewed and found that combination of structural and nonstructural measures are necessary to help reducing flood induced losses and damage in the city

3D shape recognition system by ultrasonic sensor array and genetic algorithms

This paper describes 3D shape recognition system using ultrasound pressure data and a Genetic Algorithm. The ultrasonic 3D shape recognition system using has commonly used a Neural Network (NN). However, a NN perform poorly when lacking learned data. In order to overcome this problem when using a NN, we here attempt to replace the NN with a Genetic Algorithm (GA). Unlike a NN, the GA can recognize shapes without depending on learned data. Experimental results demonstrate that the recognition ratios of the proposed recognition system using the GA are higher than that of a conventional 3D shape recognition system using a NN. Therefore, it is shown that our ultrasonic 3D shape recognition system is effective for many industrial applications. </p

Laboratory Experiment on Failure of Embankment

Failures of railway embankments in Japan usually occur during rainfall period due to the rise of water level in the embankments. Laboratory experiments were carried out to elucidate the initiation of failure of embankment under the rise of water level. The changes in pore-water pressure were monitored during the rise of water table and at the initiation of failures. The experiment results showed that main failure of embankment was initiated by development of localized unstable area at the toe of the embankment models during the rise of water level. This indicates that failure of embankments was a consequence of instability of the toe of the slope induced by saturation process under drained condition

Determination of Soil-Water Characteristic Curves of Unsaturated Sandy Soils Using Membrane Filter with Stainless Wire Mesh

Soil-water characteristic curve (SWCC) is an important soil function in an unsaturated soil mechanics field for design and analyses of any unsaturated earth structures. Determination of SWCC is not easy and more so time consuming. Generally, ceramic disc with high air-entry value has been used in the pressure plate apparatus for this purpose by many people. Now-a-days membrane filter is being used as a suitable alternative to ceramic disc. However, experience shows, it has disadvantage of breakage after one time use especially with coarse grain soils (sandy soils). In this study, membrane filter with stainless wire mesh was used to solve this problem and the SWWC was compared with the results obtained without wire mesh. Results showed that membrane filter with stainless wire mesh can be used to determine the SWCC for coarse grain soils

The basic study on measuring method of contamination of the ground and the effective porosity by using dielectric constant measuring system

For evaluating subsurface contamination, sampling method (boring) is commonly used, but this method cannot monitor the change of in-situ contamination and concentration with respect to time. The purpose of this study is to develop a measuring system for subsurface contamination in which a so-called FDR (Frequency Domain Refiectometry) and FDR-V (with Vector network analyzer) system was employed to measure the salinity and oil contaminant. This FDR and FDR-V method is a coaxial probe method, which allows the measurement of the dielectric. The experimental study indicates the possibility in measuring both the contaminant concentration and volumetric moisture content. In addition, the method for obtaining the effective porosity using this equipment was shown. Concretely, the sensor was inserted in the ground, and the liquid in which the dielectric constant differed on the water in the circumference was injected, and the method for obtaining the effective porosity from the change of the dielectric constant was proposed

Water Resources and Environmental Management in Ghana

Three principal river basins are found in Ghana and the Volta River Basin is the major one, covering about three -quarters of Ghana. The basin is shared with Mali, Burkina Faso, Cote d'Ivoire, Togo and Benin. Water from the Volta River Basin is used for drinking water supply, generating hydro-electric power, irrigation, inland fisheries and lake transport. The sustainable management of the Volta River Basin is thus of great importance. Land use activities in the basin are thus closely monitored not only in Ghana, but also in the other riparian countries as well. This paper presents information and data on the water resources and environmental management of the Volta River Basin in Ghana