The Tunnel Sealing Experiment: An In Situ Demonstration of Technologies for Vault Sealing

Abstract

A major international experiment, demonstrating technologies for tunnel sealing at full-scale, is being conducted at Canada's Underground Research Laboratory (URL) with participation by organizations from Canada; Japan, France and the U.S.A. Two bulkheads, one composed of high performance concrete and the other of highly compacted sand-bentonite material, have been be constructed in a tunnel in unfractured granitic rock at the URL. The Tunnel Sealing Experiment will characterize the performance of the two bulkheads under applied hydraulic pressures. The chamber between the two bulkheads will be pressurized to approximately 4 MPa, a value representative of the ambient pore pressures in the rock at a depth of 420 m. Instrumentation in the experiment monitors the seepage through and around each bulkhead as well as the changes to the pore water pressures, and hence changes to the flow directions, in the intact rock. Stresses and displacements in each bulkhead are also monitored. The objective of the experiment is to demonstrate technologies for construction of bentonite and concrete bulkheads and to quantify the performance of each bulkhead.