Groundwater in fractured rock mass (fissure water) which was drained during excavation work recovers its level after pumping is stopped. In the recovery process, it is expected that water goes up much faster in large fissure than in small fissure because the velocity of a laminar flow in an interstice is proportional to the square of the width of the interstice. In result, air is entrapped in smaller fissures while water goes up through larger fissures. As water seeps into smaller fissures in process of time, the entrapped air is compressed and moves slowly through paths of complex structure forming bubbles at the junction of fissures. Thus, it is expected that a mass of the entrapped air is separated into smaller masses or two bubbles are united into a larger mass. Such behavior of air in fissures may affect the storage efficiency, the leakage mechanism and the dispersive convection process of the matter such as oil, gas or nuclear wastes stored in tunnels built in fractured rock mass.
A numerical analysis is carried out to simulate the movement of the air entrapped in fissures in process of groundwater recovery. The model employed for this simulation is a fissure which branches off into two fissures of different width and joins again. This study aims to develop a numerical technique to simulate the process in which air is entrapped in a smaller fissiure and bubbles flow out of the smaller fissure into a larger fissure at the junction of two fissures. The process is treated as the moving-boundary problem. The validy of the simulation technique is confirmed by an experiment.

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Investigation of a groundwater flow system becomes important for safety assessment of underground facility, and for development of water resources. A new analysis method treating groundwater chemistry data is required along with the development of a sampling technique for the water in deep crystalline rocks. In this study, new method is developed, which estimates groundwater mixing condition using multivariate analysis and principal component analysis to the water chemistry. Computer program coded for this analysis was tested for practical use. The results were as follows;
1. Using test data, the discriminability of the mixing model was checked. The correspondence of the compositions of end-members and the mixing ratios between the pre-assumed values and the model output was satisfactory.
2. The method was applied to field data of groundwater sampled from boreholes. The result of the analysis reveals the mixing condition of groundwater and that agree with geotomography data.

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Effectiveness of dam foundation grouting is usually evaluated by Lugeon water test with a five-meter-long test section. In addition to the evaluation of average permeability of foundation around five-meter-long section, it is very significant to investigate the permeability of surface area adjacent to dam body and change of permeability due to the removal of ovberburden loading which is requisite for effective grouting.
The following investigation has been made at two fill dam construction sites which are composed of unconsolidated conglomerate. Grouting has been performed under the condition that five-meter-thick foundation remained. After the excavation of foundation and the embankment, permeability tests have been conducted with not only five-meter-long test section but also 1- or 0.5-meter-long one. Based on the results of these tests, the looseness due to the excavation and the consolidation due to the following embankment have been considered.

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This paper presented for a numerical analysis of steady-state two dimensional groundwater flow passing through a borehole which was drilled into an aquifer. The aquifer was assumed to be an isotropic homogeneous porous medium. An incompressible viscous flow in the borehole is governed by the Navier-Stokes equations, while a seepage flow in the aquifer by the Darcy's equation. These equations were numerically solved by using the finite difference method.
The numerical solutions for the stream function and the velocity in both borehole and aquifer showed good agreement with the analytical ones. The velocity at the center of the borehole in a low permeability medium was about three times as fast as that at the infinite distance in the aquifer.

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Water qualities of spring waters (NOk, NOe, NOw, and NOm) at Kokubunji City, Tokyo which springs were very closed were studied during January to December 1990. NOe and NOw are belong to Masugatanoike springs. These springs were very close and their water qualities such as anions or metals were similar.
In these spring waters we detected volatile organochlorine compounds (VOCC) such as trichloroethylene (TCE), tetrachloroethylene (PCE), and 1-1-ltrichloroethane (MC). Although sampling stations were very close, VOCC concentrations of each spring waters showed different tendency. At NOk and NOe, TCE concentraiotn was highest of three compounds. But at NOw and NOm, PCE concentration was highest of all.
Concentrations of TCE and MC had close relations at these springs. And these relations were different between NOk-N0e and NOw-NOm. At the result, it was suggested that there were the relations with TCE concentrations and MC concentrations and there ware two groundwater flows.

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