To evaluate split tensile strength of compacted core materials, we performed split tensile strength tests for compacted specimens, which were prepared using core materials for an actual rockfill dam. To estimate the effects of tests conditions, we changed the test conditions such as maximum grain size, degree of compaction and so on. Some results of split tensile strength tests had relatively large variabilities, but split tensile strength tended to become larger if the maximum grain size was smaller or the degree of compaction was larger. The ratios of uniaxial compression strength to split tensile strength ranged from 7 to 9 in this research.

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Behavior and safety of a concrete gravity dam is analyzed by three-dimensional FEM, especially focusing on the following two points; (1) the influence on deformation and safety of the dam body by placing RCD concrete along temporary forms at the transverse joint and (2) the relationship between safety against shear stress and shear strength of horizontal construction joint depending on preparation work of the joint surface. The analysis shows that the influence caused by difference of strength and stiffness of internal concrete along transverse joint is rather small, and it is thought that it can be adoptable to place RCD concrete along transverse joint. And it can be adoptable to reduce strength of horizontal construction joint considering safety factor along the joint. However, considering the safety against strong motion caused by earthquake, it is thought that a further analytical and experimental approach is needed.

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In PWRI system, one of the rock mass classification method for dam foundation, rock mass class is evaluated by the combination of rock mass three factors, that is rock hardness, fissures spacing, fissures condition. To improve such rock classification system, it is very important to correlate geomechanical values such as shear strength with the above rock factors and rock classes. Nevertheless, there was no such correlation data for many dam sites because every dam has used their own original method on the division of rock factors and its combination. Then, in this paper, authors proposed common rock mass classification method and re-evaluated 799 points of shear test sites, and clarified the differences of rock shear strength by these common rock factors based on the analysis of quantitative theory type I which is one of the multivariate analysis. As a result, shear strength depends largely on rock hardness, next, fissure spacing, and fissure condition. And also authors proposed empirical formula estimating shear strength using the above common rock factors. These quantitative evaluations and the proposed formula will be a important reference data not only for consideration of rock shear test result but also for view of rock mass classification of each dam site, specially factors combination system.

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