The dynamic response of an idealized dam-foundation system to harmonic vibration is computed by the modal analysis tequnique. The system is assumed elastic in the analysis. The frequency response functions are used to investigate the effects of dam-foundation rock interaction and the following response properties of the dam are obtained; ie, the resonant frequency of the dam decreases and the horizontal acceleration at the crest decreases, as the elastic modulus of the foundation rock decreases. The maximum response of vertical normal stress at the upstream edge of the dam is, however, not so influenced by the dam-foundation rock interaction.

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The Sabigawa Lower Dam is a concrete gravity dam being constructed by Tokyo Electric Power Company, as the lower regulating reservoir for the Sabigawa Pumped Storage Power Station.
The thermal cracking of dam concrete has been usually a major design concern and various methods have been used to control the concrete temperature.
At the Sabigawa Lower Dam, with two dimensional FEM analysis, we simulated thermal and stress behavior of the dam concrete, and determined the control value for highest allowable temperature of the dam concrete. Further to determine the placing temperature of the concrete, we conducted series of one dimensional FEM analysis, where the precooling effect of mixing ice and chilled water were incorporated into numerical model.
With thus determined procedure, we controled the placing temperature and successfully kept the temperature of the dam concrete below the highest allowable temperature.

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Hokkawa dam locates near the border between Tochigi prefecture and Fukushima prefecture. The foundation soil of the dam consists of Quaternary deposit of welded pyroclastic rocks which belongs to the Nasu volcanic zone. Piping test was performed in order to evaluate the potential of piping of the boundary soil layer between the lightly welded and moderate welded pyroclastic rocks which distributes in the right side bank of the river at the dam site.
Because the conventional method of tube sampling was considered not adequate to obtain undisturbed sample at this site, block sampling method was tried at first. However, specimen for piping test can not be prepared successfully from the soil block due to its unstable soil structure. On the other hand, in-situ piping test is recognized very questionable because boundary condition and pass of water flow are not clear.
On the basis of the above considerations, the in-situ freezing method was adopted to obtain undisturbed sample for piping test which is considered the best in the present state-of-the-art technique for recovering high-quality undisturbed sand and gravel soil sample.
Herein reported are the (1) in-situ freezing sampling method, (2) method of piping test, (3) test apparatus and (4) test results.

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Sea sands contain minute perticles little (below 0.15mm).
Therefore, when sea sands are used in concrete for dams of low cement content, we must supply them with some minute particles in appropriate methods.
We investigated supplementing methods of minute particles by fresh mortar and fresh concrete, and we decided to add slag powders to sea sands in the concrete of Nagatani Dam.
This concrete for the dam is workable and has no problem of thermal properties.
And we also made sure that it has no problem of the concrete durability.
Now, Nagatani Dam's work, using sea sands for fine agregates of concrete for dams, is going well.

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Hase Dam, being built to form the lower reservoir for Ohkawachi Pumped Storage Power Project (1.28MKW) of the Kansai Electric Power Company Inc., is the second dam by ELCM (Extended Layer Construction Method) in Japan. The dam 102m in height and with volume of 565×10³m³ is progressing at an average rate of 6 lifts (4.5m) per month and is expected to be completed in March 1992.
In this article several measures taken are described.
Some of them are:
• Mixing moderate heat Portland cement with blast-furnace slag at the batching plant on site. Binder can therefore suit properly types of mix.
• Use of once only steel form works for finishing slump concrete at lateral yard joints.
• Cooling air arround concreting using spout spray plants.

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Grouting is regareded as difficult to decrease the permiabilitiy of “Masa” (weathered granite) that naturaly shows low permiability. The author carried out the grouting test to these granite. That test consists mainly of the comparisom between 5 meters stage and 1 meter stage. Acoording to the test the author concluded some properties of homogeneous Masa.
1. It is able to avoid cracking of foundation that causes bad influence on improvement of permeability by selecting injection pressure of Lugeon test and grouting addequatly.
2. Water injection during Lugeon test and grouting causes microscopic fissures that results in the decrease of the stages of low Lugeon value (namely less than 1 Lu).
3. The selection of lower injection pressure of Lugeon test than that of grouting makes it possible to avoid the growth of fissures.

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