The Enhanced Sealing Project (Esp) - 7 Years Monitoring of a Full-Scale Shaft Seal at Canada's Underground Research Laboratory

Abstract

The Enhanced Sealing Project (ESP) is a research, development and demonstration (RD&D) project monitoring thermal-hydraulic-mechanical (THM) responses of the shaft seal at Canada’s Underground Research Laboratory (URL). The project was started in 2009 and is jointly funded by Posiva (Finland), Andra (France), and CNL (Canada) to continue monitoring until the end of 2016. The seal is intended to limit the mixing of saline groundwater below fracture zone (FZ) at ~270 m depth with fresher groundwater above it. The diameter of the shaft seal is approximately 5 m and comprises a clay component (6 m thickness) sandwiched between two concrete components (3 m thickness each). The clay component is a mixture of 40% bentonite and 60% sand and is designed to provide sealing capability. One hundred sensors were installed at strategic locations within the seal and nearby granite rock to monitor evolution of temperature, displacement, strain, hydraulic pressure, total pressure, and saturation. As of December 2015, the monitoring results indicated that the seal is functioning to limit the mixing of the saline and fresh groundwater below and above the fracture zone. Experience gained from the ESP, construction and monitoring methods are valuable to support future development and design of sealing systems to safely close a Deep Geological Repository (DGR). The ESP data combined with experimental and site investigation data at the URL site provide comprehensive data set to calibrate numerical model to simulate the performance of the sealing system in a DGR.