Abstract
ABSTRACTClay-mineral type and content, bulk mineralogical composition and alteration of bentonite are very important factors for the ultra-long-term stabilization of barriers and backfills in radioactive waste disposal. This study investigates the effects of clay-mineral type and content on the swelling characteristics and permeability of bentonite–sand mixtures with clay minerals using one-dimensional swelling-pressure and constant-pressure permeability tests. The hydraulic conductivity of bentonite–sand–clay mineral mixtures increased with increasing content of non-swelling alteration products of montmorillonite. Furthermore, hydraulic conductivity was comparable to that determined with the Kozeny–Carman equation for a specific surface area, suggesting that hydraulic conductivity may be estimated based on the abundance of expected alteration products of montmorillonite. This study provides a basis for evaluation of the hydraulic conductivity of bentonite–sand mixtures with known quantities of expected alteration products of montmorillonite.
Highlights
ABSTR AC T : Clay-mineral type and content, bulk mineralogical composition and alteration of bentonite are very important factors for the ultra-long-term stabilization of barriers and backfills in radioactive waste disposal
The hydraulic conductivity of the bentonite–sand– clay mineral mixtures increased with the mixed nonswelling alteration products’ (NSAPs) replacement ratio
To clarify the effects of clay mineral type and content, bentonite–sand–clay mineral mixtures and clay mineral specimens were subjected to swelling-pressure and permeability tests
Summary
One-dimensional swelling-pressure and constantpressure permeability tests with samples containing one clay mineral were carried out to clarify the influence of clay mineralogy on swelling pressure and hydraulic conductivity. The kaolinite, mica and chlorite were mixed with bentonite and sand to form bentonite–sand–clay mineral mixtures for onedimensional swelling-pressure and constant-pressure permeability tests. Values for talc and mica were low (Ps = 0.01 and 0.02 MPa, respectively), and that for chlorite was
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