During an earthquake, perimetral and vertical joint opening affects the seismic response of concrete arch dams by releasing the tensile stresses and redistributing the internal forces of the dam. Although the mechanism of these two types of joint openings is the same, their effects on the response of the dam are different. Perimetral joint opening, in the contact area of dam body and foundation, releases the relatively high tensile cantilever stresses at the base of upstream face and increases the radial displacement of the dam toward downstream direction, whereas vertical joint opening between cantilevers of the dam releases the arch tensile stresses and cantilever action resists the internal forces by bending toward upstream which results an increase in cantilever compressive stress at the base of upstream face.

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For the purpose of better improvement of the concrete workability, the characteristic of the RCD concrete with a large quantity of fly ash is examined. The results of this study show that in the case when concrete is mixed with fly ash about three times compared to as usual, it is able to decrease an amount of water per unit, to reduce the change of consistency, and to increase the long-term strength, without changing of the properties of compaction and heat of hydration.

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In the experiments to evaluate durability of materials influenced by acidic water or sulfate, test pieces made of regular Portland cement and blast furnace cement B were kept in acidic solution and the changes of their compressive strength and permeability coefficient were examined. As a result, it is clarified that the acidic water had little influence on the material in the case that pH was around 3, but the sulfate had some influence such as decreasing of compressive strength or increasing of permeability coefficient even in its low concentration.

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When the best construction method for a project is selected from among some ones, it is usual for the experts of construction to evaluate them qualitatively based on their subjectivity and sensibility because quantitative analysis by effect functions of construction method is difficult. However, such a way has a question in the assurance of transparency and validity of the selection result. The authors pay attention to AHP (Analytic Hierarchy Process) which can quantitatively analyze human sensibility, and propose the synthetic evaluation technique to which it is applied. The paper reports on the technique and the consideration through the model case of dam constructions.

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Recently, the rationalization of evaluation of dam foundation grouting effects using geotomography has been studied enthusiasticaily. Test grouting was carried out at a site, which was composed of Pliocene sandstone. Resistivity tomography was used for the evaluation of grouting effects. Before the detailed analysis of the results of the resistivity tomography, laboratory measurement of the resistivity of cement-based grouts was made, varying their density and age. Based on the results of laboratory tests and the distribution of grouted veins observed in the grouting area, the possibility of the more rational evaluation of grouting with resistivity tomography was discussed.

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A system has been developed to secure stable working efficiency and safety when constructing concrete dams, and as a countermeasure against a shortage of skilled workers. This system was used in Niigata Prefecture Oku-Miomote Dam Project and displayed good performance which was equal to the skill operator. The present paper outline the system and describes some observation results on automatic operation.

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