Stability of rock-fill type dam should be p roperly evaluated before its first impounding, because it has been reported that some fill type dams have collapsed and/or damaged in the course of the first impounding. A new technique for the stability evaluation was developed by combining stochastic and analytical methods. In this technique, the pore pressure change is predicted by using genetic algorithm and artificial neural network models, then the stability of dam is evaluated by analytical method based on the Sekiguti-Ota model. Stability of the Minamiaiki dam was evaluated by employing this method. This new technique could be successfully applied to the prediction of pressure change and evaluation of stability for real dam.

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Methodology for estimating the hydraulic parameters of the deep underground using single-hole test methods has been developed. A method of using sequential test to identify suitable test event was applied. This sequential test method is being started from pulse test to see rough estimation of permeability. Based on the permeability by the pulse test, slug test and/or pumping test followed by recovery test are carried out. The analysis method combined the pressure derivative technique with the semi-log straight line method. This test methodology was applied to a series of single-hole packer tests in granitic rock which demonstrated the efficacy of the approach. Real time plot of the test data with pressure derivative during the testing is effective for the decision of the data quality.

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The seawater/freshwater interface at depth is influenced by fossil waters and other parameters, making its analysis more difficult than for shallow aquifers. Since the dynamics of the deep seawater/freshwater interface is poorly understood, an evaluation method combining both in-situ observations and numerical analysis is necessary (e. g. this is specially true in projects like geological disposal). The movement of the seawater/freshwater interface was observed to a depth of 200 m in the sedimentary soft rocks of the Quaternary and Tertiary of Tokai Village, Ibaraki prefecture (japan). Seawater intruded during pumping (average of 10,000 m³/d) related to the construction of a ring-like tunnel, as a part of the construction of a proton accelerator complex. Initially, the seawater/freshwater interface was simulated under original conditions. Based on these results, four monitoring wells were drilled during the pumping period. Electric conductivity and temperature were continuously, _ measured. Differences in the seawater intrusion patterns within the Quaternary and Tertiary sedimentary soft rocks were as follows. (1) Electric conductivity show ed that seawater intruded into the Quaternary during the 13-22th months of pumping, but there was no salinization in the Tertiary. The vertical migration of salts was prevented by the aquitard below the intruded aquifer. The permeability of this barrier was 1/10-1/100 of the upper aquifer. (2)Rises and drops of temperature were observed at various depths during pumping. For example, temperatures drops were observed at the seawater intrusion depth during the 11-12th months of pumping, and on the 18th month at the boundary between the Quaternary and the Tertiary. Salinity at the Tertiary might be related to other sources aside of present seawater intrusion. (3)The seawater/freshwater interface in the Quaternary and the Tertiary were simulated without pumping. The position of seawater/freshwater interface was in good agreement with the monitoring data, but it was difficult to calculate the salts concentration in the Tertiary sediments. It is thought that under static boundary conditions, even if the position of the simulated seawater/freshwater interface is valid in the shallow area, it may not be adequate for simulations at depth.

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Groundwater simulation using spreadsheets is proposed, because the spreadsheets software is widely used at home and scientific calculations. Three applications are shown in this report: 1-dimensional unsaturated flow simulation,1-dimensional solute transport simulation, and 2dimensional groundwater flow simulation. Advantages of this method are summarized as follows: (1)Knowledge of computer programming rules is not demanded, (2) Numerical results can be visualized easily, (3) It can be used to check boundary conditions of self developed numerical codes, (4) It can be used as educational tools for beginners in the learning stage of groundwater simulation.

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