In case of permeability tests for soil materials of filldams, we usually use the specimens which are made in compaction tests. Even if allowable maximum grain size condition is satisfied for compaction tests, that is not always satisfied for permeability tests. Our study has proved that the accurate test results can be obtained in not only compaction tests but permeability tests, if the ratio between diameter of permeameter and maximum grain size of soil materials (φ/D_max) is larger than 4-5. Furthermore, we doubted that we underestimated the permeability of specimen made with compaction because of the consentration of finer particles at the bottom of specimen. From the results of our tests, we can maintain that we do not have to pay much attention to this phenomenon in permeability tests for soil materials. But we have emphasized that we should measure the change of coefficient of permeability in time during falling-head permeability test.

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Recently green cutting (laitance removal) in dam construction in Japan has been confronted by two problems. Firstly the large work areas that need to be treated when using the RCD (roller compacted dam) construction method and secondly undesirable work environments. This system is designed to solve these problems by automating the removal work. The system consists of travelling green-cutting unit, a support unit composed of a superhigh pressure pump and a vacuum pump and a path guidance system. The travelling unit washesout laitance using a superhigh pressure water jet (maximum 1000kg/cm²) and removes the dust by suction while travelling automatically under control of an optical communication pathguidance system for bidirectional automatic tracking. This system contributes to rationalizing the treatment of construction joints in several ways:
1) Its removal power can be adjusted (by changing water pressure, stand-off distance, etc.) therefore the work period is not limited by the extent of hardening.
2) Treatment capacity is improved. (100 to 150m²/h)
3) Manpower id saved.
This paper reports development process, system outline, developed techniques, and result of field tests in an actual dams site.

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