A high head gated outlet at a tunnel may cause cavitation and gate's vibration in case of subatomospheric pressures occurs at a high velocity flow entraining the air. To avoid severe subatomospheric pressures, the adequate amount of the air have to be supplied to the outlet through the air vent located downstream of the gate. In order to estimate the amount of air supply, and to make clear the characteristics of the air-entrained flows, we implemented the field measurements of air demand at Agigawa Dam and carry out the hydraulic model tests. Based on the results of these tests, we developed the simulation model for air supply estimation.

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The mechanism of hydraulic fracturing in the core-type rockfill dams was studied in this paper. Series of laboratory seepage fracture tests were carried out on fill materials to investigate the relationship between the hydraulic gradient at failure and the effective confining pressures. Finite Element stress analysis was made on Teton dam, to examine the process of stress redistribution in the core zone due to wetting and the local stress states to be compared with hydraulic conditions. These results were summarized to propose a practically useful procedure of evaluating the posibility of hydraulic fracturing in rockfill dams.

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The Hyogoken-Nambu Earthquake occured on January 17, 1995. The Richter Magnitude of the earthquake was estimated to be 7.2. Fortunately, no damage was caused by the earthquake to Hitokura Dam situated 47km northeast of the epicenter. However, on seismographs placed in the upper- and lower-level inspection galleries, accelerations as large as 483 Gal and 183 Gal, respectively, (both in the horizontal direction) were recorded. The paper describes a two-dimensional FEM dynamic analysis performed using seismograms recorded at Hitokura Dam to evaluate the damping constant of the model used and the effect of vertical waves. A comparative dynamic response analysis was also performed using seismograms recorded during previous earthquake incidences. Following findings were obtained from the analysis. Analytical values correspond most closely to measured values when 10% was used for the damping constant, indicating the propriety of use of the value. The effect of the vertical components of incident waves could be best simulated when both the vertical and horizontal components were considered. However, no marked variations were observed in stress response values, indicating that the effect of vertical waves on stresses is small. The results of a comparative response analysis, which was performed using four different waveforms, namely, Hitokura, Narugo, Susohana and Tarumizu, and assuming the maximum acceleration to be 200 Gal, show that the maximum dynamic stress was induced by Hitokura wave.

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More than 20 years has been passed after begining of RCD research, and more than 20 RCD projects have been built. Through those research and practical construction, considerable technical development has been accomplished. However, aggregates for RCD concrete are substantially same as those for conventional dam concrete. Point of view of using lower quality aggregates, several effects of fine material of aggregate are described in this report. Documents are mainly based on the information getting from experiments at Laboratory of Water Resources Development Public Corporation.

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The slaking experiment guidelines of foundation rocks have been established by several professional societies and Public Works Research Institute of Ministry of construction. However all of them take soft rocks as experiment objects. So far there is no slaking experiment guideline for medium-hard foundation rocks, which exists in Ishiuchi Dam with 430kgf/cm² of uniaxial compressive strength. After deeply understanding the basic ideas of existing guidelines and specifically investigating the characteristics of the foundation rock in Ishiuchi Dam, the slaking experiment, analysis and construction method are studied.

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At Kaore arch dam consutructed for upper reservoir of Okumino pumped-storage power plant, behaviors of dam and foundation rock are measured elaborately in order to inspect design conditions and carry out safety test filling. In this paper results of measurements and analyses are shown from the beginning of test filling. And useful results for design and construction of arch dam are introduced.

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