Permeameter Studies of Water Flow through Cement and Clay Borehole Seals in Granite, Basalt and Tuff

摘要

Boreholes near a repository must be sealed to prevent rapid migration of radionuclide contaminated water to the accessible environment. The objective of the research is to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. Flow through a sealed borehole is compared with flow through intact rock. Cement or bentonite seals have been tested in granite, basalt, and welded tuff. The main conclusion is that under laboratory conditions, existing commercial materials can form high quality seals. Triaxial stress changes about a borehole do not significantly affect seal performance if the rock is stiffer than the seal. Temperature but especially moisture variations (drying) significantly degrade the quality of cement seals.