Sealing Performance of Bentonite/Crushed Basalt Borehole Plugs.

摘要

Mixtures of crushed rock and bentonite are considered for backfilling and sealing high-level nuclear waste repositories. Many variables affect the hydraulic conductivity of such mixtures, including the size and shape of the rock particles, method of mixing and emplacement, water content and density of the clay, and the weight ratio of rock to clay. Mixtures of crushed basalt and bentonite have been tested in two types of permeameters, 20 cm (8 in) diameter stainless steel permeameters and 10 cm (4 in) diameter PVC permeameters. Preliminary results show that a mixture of 75% crushed basalt and 25% bentonite has a hydraulic conductivity between .0000000010 cm/s and .000000025 cm/s. In some cases, preferential flow paths have developed (possibly as a result of the montmorillonite washing out of the crushed rock matrix), giving hydraulic conductivities as high as .0001 cm/s. Other ratios of rock to clay have similar bimodal results.