Dynamic nonlinear FEM analyses have been carried out on a concrete arch dam, in which the nonlinearity due to joint opening and the material nonlinearity of the dam have been taken into account to investigate the influence of both kinds of nonlinearity on the earthquake response of the dam. Taking the material nonlinearity into consideration in addition to joint opening, considerable permanent displacement and considerable amount of joint opening occur in the response of the dam. Perimetral joint opening at the contact area of the dam body and its foundation together with material nonlinearity releases the cantilever tensile stresses at the base of the upstream face and increases the arch compressive stresses at the mid-height of the crown cantilever. During vertical joint opening between the cantilevers of the dam accompanied with material nonlinearity, the tensile stresses can not develop across the joints, and so arch tensile stress release occurs in that area. The dam has more remarkable tendency to displace toward upstream and downward directions, which results in considerable increase of compressive stress in cantilever at the base of the downstream face. The release of the tensile stresses and the redistribution of the internal forces by converting the cantilever action to the arch action or vice versa due to the joint opening in concrete arch dams are accelerated by the material nonlinearity. It may be said that the above process results in the stable stress state in the actual dams.

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A draft gate which is effective to reduce not only manufacturing but installation cost is presented. The draft gate presented here has feature that a gate casing and transition tube are fabricated in one block in firm by reducing their dimensions in flow direction; that reduce fabrication weight about 20% in comparison with conventional one. Hydraulic head loss increases for the presented type, however, the increase is about 0.035mAq for flow velocity of 5m/s, in other words, about 0.01% of total head of pumped storage power station in current design. The presented type is to be installed in a pumped storage power station of 1, 800MW, final capacity of 2, 700MW, in Japan.

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Water sheet jet through clearance of dam gate rubber seal appears when a inflatable seal is unloaded to change the dam gate opening. The jet attacks equipment or construction near conduit outlet, causing them some damages. Authors present a flow guide to turn the sheet jet to a mild inner flow, using a vacant space in guide flame. The guide consists of plates in raw and a flow channel. Special feature of the plates is that they are set with not only attack angle but dihedral angle against the jet. Optimum angles and configuration of the channel were examined by experiment. The guide presented here is to be installed in a dam gate of head of 106m in Japan.

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In the present study, we developed a stochastic analytical code to generate the hydraulic conductivity field with a lognormal distribution and a special correlation. Seepage analysis was made using hydraulic conductivity fields generated as models of dam foundations. Based on analytical results, the influence of variability in hydraulic conductivity field on the amount of underseepage and the safety against seepage failure of dam foundations, and the effects of curtain grouting in heterogeneous hydraulic conductivity fields were discussed.

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In this study, in order to propose “the technique which is useful for the reservoir management”, the sediment discharge rate from the basin was investigated by field measurements for five years in Shichikasyuku reservoir. There was the significant correlation between turbidity and SS. It is possible to always estimate the quantity of SS carried into the reservoir by measuring turbidity and transforming it by this regression formula. A method for estimating the amount of fine sediment during one flood is proposed. The calculated total amount of sediment which flow into the reservoir after construction of dam was approximately equal to the measured amount of sediment on the reservoir bed, the usefulness of this method was shown.

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