In this study, environmental impact of fine-grained dam sediment in the usage of material supply to rivers was discussed through laboratory tests. Dredging, transportation and putting sediment to downstream river was considered as a common method and the granular-forming treatment by cement stabilizer was mainly examined. The degree of concentration of suspended sediment and alkaline influence by the cement addition were focused as main two factors on environmental impact. Laboratory tests such as abrasion tests in the water and erosion tests by the running water were carried out and these test results were examined from the viewpoint of actual designing of sediment supplying to rivers. And it is made clear to reduce the degree of concentration of suspended sediment and to raise the possibility of recycling of fine-grained dam sediment as material supply to rivers by means of simple treatment.

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The coarse-grained materials as a whole are the rock and soil mixtures with the wide range of particle size, from the massive rock with hundreds mm of diameter to the fine soils. The design density and its quality control limits are determined through a series of indoor compaction tests using the downsized samples, the larger size portion being cut off, along with the particle size correction (for example Walker-Holtz method) in the conventional design procedure. However it is almost impossible at the moment to predict the field compaction density satisfactorily from the indoor test results, because the method of compaction and the distribution of the particle size in the field embankment differ greatly from the indoor compaction condition. On the other hand, the well-known and widely used replacement method is not appropriate for the coarse material, because it cannot afford sufficient number of sampling data enough to evaluate the reliable field density from its persistent character, i.e. labor intensive and time consuming. We carried out a series of field test embankments under the several different water content condition, to simulate the indoor compaction test for the two cases of coarse fill materials. In order to evaluate the most reliable compaction density, the newly developed RI density meter of scanning type (SRID) was used in the field embankment tests. SRID has sufficient sensitive volume, roughly ten times as large as the conventional RI density meter, and its density sampling capacity is far greater than the replacement method, so applicable to the coarse materials and suitable to the multi-data sampling. In this report the field test results are shown and the correlation of the compaction characteristics in the field compaction work with the one in the indoor compaction tests are discussed.

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CSG has been rapidly developed as the new materials in the civil engineering field in the recent years. It was originally used as the materials for the temporary facilities, but is going to be used as the materials for the permanent facilities. CSG has the properties varying in a wide range because of its production process. So, it is the fundamental issue to clarify the magnitude of the material safety factor, in order to assure the safety of the CSG structures. This paper discusses the magnitude of material safety factor of CSG from the view of statistics and probability.

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Since the signal of a vibrating wire sensor is digital and it is not influenced of voltage resistance or current, it is advantageous to time devended behavior, moisture resistance, or an insulated fall. Therefore, this can collect the reliability data of the engineering works for a long time. In this research, this was installed in a dam or the basic foundation. And the performance of instrument which was being used until now was compared with this.

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