[en] As an engineered barrier system in the geological disposal of high-level waste, multibarrier system is considered. Multibarrier system consists of the vitrified waste, the overpack and the buffer. Bentonite is one of the potential material as the buffer because of its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. As the construction technology of the buffer, the block installation method and in-situ compaction method, etc, are being investigated. The block installation method is to emplace the buffer blocks manufactured in advance at the ground facility, and construction processes of the block installation method at the underground will be simplified compared with the in-situ compaction method. However, the block joints of buffer might be a mechanical weak portion or might be a preferential flow channel. Therefore, it is necessary to evaluate the effect of the block joint of buffer. On the other hand, the in-situ compaction method is to introduce the buffer material with specified water content into the disposal tunnel and to make the buffer with high density at the site using a compaction machine. In regard to the in-situ compaction method, it is impossible to construct the buffer at one time, the construction joints will be exist. In order to evaluate the effect of block joints, the box shear test was conducted for mechanical properties, and the infiltration test and permeability test were conducted for hydraulic properties. As the sample of in-situ compaction method, the buffer that was recovered from the Kamaishi In-situ THM Experiment Site was used. Furthermore, the shear properties between the buffer and rock was obtained. The results obtained in this investigation are as follows, 1) The strength of the specimen at 50% saturation is higher than that of the specimen at 100% saturation. 2) When the degree of saturation is 50%, the shear strength of the block joint is far smaller and weaker than that of the block. Therefore, the deformation of the buffer might be occurred at the block joint. 3) If the deformation at the block joint is only sliding, the joint part may not open. However, the joint part might open when the bentonite block is failure. 4) When the degree of saturation is 100%, the strength of the block is weaker than the case where the degree of saturation is 50%, but the difference between the block and block joint is small. In short, saturation of the buffer reduces the strength as a whole, but formation of extremely weak portion does not seem to occur. 5) As the saturation period is long, the adhesion of the block joint is strong. As a result, the shear strength of block joint is higher. 6) As compared with the interface between the bentonite block and rock, the bentonite block joint is weak when the saturation period is short. However, as time past, the strength of the bentonite block joint becomes high, and the interface between the bentonite block and rock becomes weak portion. 7) The initial seepage of the specimen that includes the block joint is quickened because of the influence of the block joint right after the blocks are emplaced. However, the influence of block joints becomes small after saturation of the buffer. The influence of construction joints also becomes small after saturation of the buffer. (author)