Field Test of Ethanol/Bentonite Slurry Grouting into Rock Fracture
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Field Test of Ethanol/Bentonite Slurry Grouting into Rock Fracture Motoyuki Asada1, Hitoshi Nakashima1, Takashi Ishii1, and Sumio Horiuchi1 1 Institute of Technology, Shimizu Corporation, Echujima 3-4-17, Koto-ku, Tokyo 135-8530, Japan ABSTRACT Crystalline rocks have fractures which may cause unexpected routes of groundwater seepage. Cement grouting is one of the most effective methods to minimize seepage; however, cement materials may not be suitable for the purpose of extra-long durability, because cement is neutralized or degraded by chemical and physical influence of chemical reaction. Natural clay like bentonite is one of the most promising materials for seepage barrier; however, water/bentonite grout is so viscous that enough amount of bentonite can not be grouted into rock fractures. To increase bentonite content in grout with low viscosity, the utilization of ethanol as a mixing liquid was studied. Ethanol suppresses bentonite swelling, and more bentonite can be injected more than that of water/bentonite slurry. In this paper, grouting into in-situ rock mass fracture from the ground surface was tested to investigate the barrier performance and workability of ethanol/bentonite slurry as a grouting material.
INTRODUCTION The safe disposal of radioactive waste is a key requirement of the nuclear industry worldwide [1]. At radioactive waste disposal facilities, leaks of radionuclides from vitrified wastes to the ground surface will be prevented by engineered barriers (metal containers and buffer) and natural barriers (low permeable rock mass). Disposal facilities of radioactive waste from nuclear power plants must be constructed at the geologically stable place to isolate radioactive waste safely. Seepage control is one of the most important issues at the construction stage of such facilities, because leaks of radionuclides must be prevented by the movement of groundwater. Natural barriers of rock mass have been located in geologically stable place for long time and would have high barrier ability; however, in the rock mass there are some fractures which have high permeability. They may become flow paths of radionuclides from waste containment facilities to ground surface. Grouting barrier materials into these water pathways of rock mass can decrease the risks of radionuclide leaks. In common, cement is used for sealing water pathways in the field of dam and tunnel construction. Some cement particles have average diameters of several micro meters and they can be grouted into 0.05mm cracks, however, artificial materials like cement may decrease its barrier quality within a certain period although waste containment facility must keep seepage control for more than 10,000 years. Cement material is neutralized or degraded by chemical and physical influence of chemical reaction. There are also possibilities of risks due to ground deformation such as landslides and collapse of fractures. On the other hand, natural clay like bentonite is one of the most promising materials for seepage barrier grouting of long durabilit
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