By the 2011 off the Pacific coast of Tohoku Earthquake, Fujinuma dam collapsed, and the disaster caused many deaths. This study, performs a dynamic response analysis of Fujinuma dam, and calculates residual deformation amount by residual deformation analysis applied Watanabe-Baba method assumed arc slip, and compares the measured crest settlement with the observed crest displacement leading to the dam collapse. As a result, it is possible to estimate the strength parameters of Fujinuma Dam, but if not taking into account the reduction in strength crest settlement amount is fairly small, and if strength reduction occurred the crest settlement reached to the difference between the heights of the dam crest and the high water level when collapsing. The major reason why the large crest settlement has occurred in the dam, are the density decreases and lack of strength due to no compaction. The residual deformation analysis was performed, it is possible to explain the residual settlement of Fujinuma dam, and it could prove to be high applicability of the residual variant.

In dam construction, the confirmation of dam foundation rock is important. So far, the evaluation of dam foundation rock is generally a “hammering test” and “visual confirmation of the crack state” by experts have been carried out, neither the criterion of evaluation item are qualitative, rock mass may differ by rater. The authors, in addition to the conventional process according to experts, was applied “The knocking ball test” can quantitatively and quickly measure the elastic modulus of the rock in situ. By “The knocking ball test”, it is possible to quantitatively evaluate the hardness classification. We were able to smoothly advance the dam foundation rock inspections conducted under the dam operators and technician attendance.

The conditions for efficiently removing phosphorous from lake water by using a high-speed phosphorous adsorbent were investigated. When lake water was passed through a column packed with the adsorbent in downward flow, stable phosphorous removal was possible. However, pretreatment for removing the suspended solids was required in order to prevent clogging of the column. Thus, in order to eliminate the pre-treatment, upward flow was also investigated. As a result, the column did not clog even without pre-treatment. Furthermore, although the phosphorous removal properties were degraded relative to those in downward flow, the concentration of phosphorous was lowered by adsorption treatment to below the level negligible for eutrophication.

The safety factor for shearing and the safety factor for inner principal stress are studied mathematically in the structure design of concrete gravity dams. Further, the difference in the characteristics of these two safety factors is analyzed. The consistency of these two safety factors is also discussed in comparison of the specified values in the concrete gravity dam design.