A gel formation of the bentonite at the interface was
found to be a dominant process in the erosion of
bentonite particles whereas the intrusion of bentonite
gels into the rock fracture by a swelling pressure was
observed to be small. It is also observed that the erosion
of the bentonite particles is closely related with a gel
formation and the stability of the bentonite particles,
which in turn strongly depends upon the groundwater
chemistry. Consequently an erosion of the bentonite
particles in a natural groundwater is considerable and
the eroded bentonite particles are expected to be stable
at the given groundwater condition.