Pilot study of method for constructing concrete seals and fracture grouts in deep boreholes, and cementitious backfills in tunnels, drifts and shafts in crystalline rock: Theoretical modeling and experimental study

Abstract: Borehole sealing is required for different purposes, like permanent tightening of deep holes
bored in conjunction with site investigations for location of radioactive waste repositories, and
temporary plugging of holes carrying water in deep mines. The holes will pass through low-permeable
rock as well as through water-bearing fracture zones. Sealing can preferably be
made by use of concrete where such zones are intersected, while very low-permeable clay
seals can be placed where the holes are surrounded by tight rock. This study focuses on with
concrete seals, and on grouts used for stabilizing intersected fracture zones before borehole
sealing is started.
The work on concrete comprised comparison of two recipes with different superplasticizers,
i.e. organic Glenium which is currently used on a large scale, and talc being an inorganic,
hydrophobic material. The study included determination of the compressive and tensile
strength as functions of time, and fluidity, pH and hydraulic conductivity of matured concrete.
Part of the study concerned grouts for sealing of rock fractures. Two cement brands were used
as for the concrete study. The effect of adding palygorskite and talc to the silicious aggregate
material for enhancing fluidity was tested. The work included determination of properties like
strength and fluidity.