Upon entering full scale production, Cigar Lake is envisaged to be the largest high grade Uranium Mine in the world. Despite several recent setbacks, the Mine finally entered production in March 2014.
On this project, Alan Auld Engineering Ltd [AAE] was responsible for the detailed design and supervision of a 200m long arched tunnel built as a refurbishment of a circular 4.2m concrete segmental tunnel, and, the design of cross cut tunnels, both using the New Austrian Tunnelling Method [NATM] process of shotcrete and rockbolts in conjunction with engineered yielding elements. The Tunnels are designed to support ground conditions of mixed RM1-RM3, with accommodation for deformations due to expansion loading from the artificial freeze and stress redistributions following ore extraction.
During this job AAE provided a site team of engineers and inspectors to teach local contractors the implementation of the Alpine tunnelling method, we also provided specialist site supervision to monitor rapidly changing ground conditions and to provide decision making support by use of Required Excavation and Support Sheets (RESS).
AAE are proud to have achieved increased performance as a result of a recommended change in design philosophy from a stiff high strength pre- cast segmental design to a NATM style flexible liner with yielding elements. We are also proud to have improved safety due to controlled deformation in the NATM and refurbished tunnels.
Furthermore, extensive and on-going deformation and stress cell monitoring, as suggested by Alan Auld Canada Ltd helped provide a greater understanding of the effects of tunnelling, adjacent tunnelling, ore extraction and freezing. From working on this project, we greatly improved our knowledge and experience of tunnel development within a complex geology incorporating freezing and jet boring.