The Hokusatsu Tunnel constructed in the Hokusatsu region of Kagoshima Prefecture, a large amount of groundwater containing a high arsenic concentration was gushed during excavation. The impact of that to the local water environment was a big issue. In order to decrease the amount of gushing groundwater, in the section where observed huge amount of water inflow and the high arsenic density, the rock grouting with ultrafine cement was applied. As the result, the water flow was enormously reduced. In this study, authors established a method to control the construction of grouting from tunnel and to evaluate the effect of grouting improvement through water reduction measures using ultrafine cement for cracked rocks. In addition, the grouting improvement effect after the completion of the standard holes can be estimated from the approximate formula between the Lugeon value and the density of the grout hole. Furthermore, it was found that the grouting improvement effect was related to the density and the opening of the joint in the rock, and the intersection angle between th e grout hole direction and the joint direction.

When observations of groundwater levels or groundwater qualities are made in coastal hydraulically highly permeable strata using stationary auto-logging devices, the collected observation time-series data often contain semidiurnal and diurnal oscillations caused by predominant tidal components as well as longer-period components due to atmospheric-pressure changes and other agents. Because the periods or frequencies of the predominant tides are accurately known, the tidal and longer-period components in observation time-series data can be separated from each other using a digital filter that screens fluctuation components by frequency. This paper presents and evaluates low-pass digital filters for 30- and 10-minute-sampled time series that reduce or eliminate the predominant tidal components with diurnal and shorter periods while preserving longer-period components. The presented filters are the simplest running-mean filters, cosine filters using windows, and, for 30-minute-sampled time series, a newly produced tide-killer filter designed to completely eliminate the specific predominant tidal components. These nonrecursive filters are easy to apply to time-series data using built-in functions of spreadsheet software. They would be useful for processing groundwater observation time-series data collected from coastal areas.