Recent molecular dynamics simulations and spectroscopic approaches indicated that water molecules confined in nanometre scale has a constrained structure with shorter hydrogen bond distances. In order to verify a hypothesis that ionic diffusivity in rocks should be affected by the constrained molecule structure of water in nanopore, we measured the effective diffusion coefficients of iodide ion in rocks by through-diffusion experiments. We also studied the quantitative relationship between the diffusion coefficients and the pore structures. Most of effective diffusion coefficients for rocks can be explained by the power law with effective porosity, while those of the samples involving abundant nanopores were much lower than this relation. By an assumption of the power law between effective porosity and tortuosity, the ionic diffusivity through nanopore water can be estimated. The value is about one order lower than the diffusivity in “free” pure water, and relatively lower with smaller pore size. The similar effect has been suggested by permeability modeling with the consideration of the constrained molecule structure of water in nanopore. This consideration can be important for the quantitative estimation of mass transport properties through rocks.

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In the hydrogeological characterization of sedimentary rocks, hydraulic properties of fault and cap rock structure are important factors. Although, the certainty of hydrogeological model depends on the amount of geological or hydrogeological data mainly obtained from boreholes, it is indispensable to make an outlined model from small amount of data obtained in the early stage of field investigation, and improve the details of the model as the data are obtained. In sedimentary rocks, each aquifer often has the different hydraulic head caused by various reasons such as surface topography, long-term change of sea level, or cap rock structures that were not explicitly observed in geological investigation in boreholes.
In this paper, we use the vertical hydraulic head distribution obtained in the pressure monitoring or the water level during the drilling of boreholes as the observed data, and applied numerical inversion code iTOUGH 2 to construct alternative hydrogeological model in Horonobe underground research laboratory site of Japan Nuclear Cycle Development Institute. We applied random sampling for the coverage of assumed cap rock, and two models for the hydrogeological structure of faults in the study were performed. The followings are the main results of this study.
1) It is necessary to assume the low permeable cap rock structure that was not clearly observed in boreholes, to reproduce the deep high-pressure zone as a characteristic hydraulic feature in this site.
2) The numerical inversion with random sampling of cap rock model shows that if the cap rock coverage is greater than 75%, the observed hydraulic head profile can be reproduced.
3) Hydraulic head profile of the deeper zone is controlled by the hydrogeological structure of steep fault in this area. Thus, the increase of hydraulic head profile in the deeper zone, and the numerical inversion can determine the hydrogeological structure of fault.
4) Hydrogeological structure of fault dominates the vertical groundwater flow in the vicinity of faults.
From these results, the numerical inversion using the head distribution is proven to be a useful method to construct preliminary but quantitative hydrogeological model from small amount of data obtained in the early stage.

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Rock mass failure can cause considerable damage, such as that suffered during the 1996 Toyohama Tunnel Collapse in northern Japan. Therefore, a hazard map using GIS for rock mass failure is studied as one of the disaster prevention and the management techniques. For making the hazard map using GIS, authors have already proposed a probability prediction method of the hazard area using multivariate statistical analysis. In this study, we verified the prediction method as applied to actual failure examples, and evaluated the debris scattering pattern based on literature data. Understanding of the debris scattering pattern is important in order to make the hazard map.
As a result, it became clear that this prediction method could be applied actual failure samples if the failure type is a rock mass failure. When we regarded the debris scattering pattern on the prediction as a rectangle that makes total horizontal reach and spread width, it was admitted that actual debris fell within the range of 40-60% of the rectangle i. e., the accumulation distribution probability. However, the actual debris scattering pattern may spread depending on slope conditions farther than the prediction value. Considering these results, we will aim at construction of a hazard map system using GIS for rock mass failure.

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In this paper the authors describe the way, by using the sketch of ore vein which was recorded in the period of the mining operation of mineral resource deposit, to estimate the scale of subsurface fault that is difficult to be confirmed by geological survey. From the analysis on the width of veins, it has been found that fault vein has a periodic geometric pattern with its general figure. Adopting the suppositions that can make a rational explanation on the figure of fault, displacement of movement as well as length of fault has been estimated.

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