The knocking ball test is the in-situ handy test developed by the authors to measure deformation characteristics of rock materials and rock masses quickly. The principle of this test is based on the Hertz theory which is the classical contact mechanics but still the suitable solution for non-adhesive contact problems of two elastic bodies. First, this paper shows the correlation between the elastic moduli (E₅₀) obtained by uniaxial compression tests and the elastic moduli acquired by the knocking ball tests (E_kb). As a result, it is found that multiplying E_kb by the correlation coefficient of 1.65 gives the E₅₀. Second, a deformation modulus, a tangential and secant elastic modulus, which are gained by uniaxial cyclic compression tests, are compared with E_kb so as to corroborate the strain level of E_kb. Consequently, it is confirmed that the strain level of the test is roughly similar to the one of laboratory tests. Finally, the knocking ball tests are applied to determine the rock mass classification and to evaluate aggregate quality. The result of the former shows that E_50,kb has a possibility to be a property which helps determine the rock mass classification promptly on site. And the latter suggests that the knocking ball test is more useful and appropriate than the Schmidt rock hammer to obtain reliable elastic moduli of aggregates.

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In order to estimate the state of anaerobic layer formation in the reservoir bottom and the resulting water quality problem in the JWA dam reservoirs, we examined the seasonal fluctuation of the vertical distribution of dissolved oxygen concentration and other parameters in each reservoir. We found that 66% of the dam reservoirs with no hypolimnion aerators (8 out of 12 reservoirs) form anaerobic layers. They are categorized into three groups: reservoirs having anaerobic layers from autumn to winter (four reservoirs), from summer to winter (two reservoirs), and throughout the year (two reservoirs). In addition, this study suggests the possibility that frequency of the anaerobic layer formation depends on not only total phosphate concentration of the reservoir (an eutrophication indicator) but also the vertical distance from the discharge equipment to the dam bottom. Moreover, it is likely that the downstream problem of hydrogen sulfide odor occurs when the dam has the spillway located at a relatively lower position.

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On 11^th March 2011, the 2011 Tohoku Earthquake occured. The Earthquake caused some cracks, total length of which reached to 1,547m, in the asphaltic facing of Numappara Dam which J POWER owns. After the earthquake, water leakage through the cracks increased and then the dam water level was drawn down immediately in control. We just managed to succeed in the crisis response of the reservoir water leakage and it is greatly desiable to share empirical knowledge for possible crisis management in the future. With such a backgroud, we have edited the “Record of Crisis Response in Numappara Dam on the 2011 Tohoku Earthquake”. This paper shows the outline of the damages, our actions taken just after the earthquake and konwledge learned from this crisis.

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