Geotechnical monitoring of tunnel boring machine drivages at the Donkin-Morien Mine, Nova Scotia

CIM Bulletin, Vol. 81, No. 915, 1988

J.L GILBY, C.M.K. YUEN,Golder Associates (Eastern Canada) Ltd., Mississauga, Ontario and T.R.C. ASTON, Cape Breton Coal Research Laboratory, CANMET, Energy, Mines and Resources Canada, Sydney, Nova Scotia

The access tunnels for the Donkin-Morien Mine in Cape Breton, Nova Scotia, comprise (wo parallel tunnels driven through a sedimentary sequence of sandstone, siltstone and mudstone to intersect the Harbour Coal Seam under the Atlantic Ocean, approximately 3.5 km offshore (Fig. 1). The No. 2 tunnel was driven a total distance of 3579 m using a 7.6 m diameter Lovat full-face tunnel boring machine (TBM) and was supported by steel sets. The No. 3 tunnel was initially driven a distance of 1027 m using drill and blast methods (dimensions 7.6 m wide by 5.3 m high) supported by rock bolts and shotcrete. This tunnel was then completed (from March 1986 to February 1987) using the tunnel boring machine to a distance of 3573 m. During the period May 1983 to December 1984, a major geotechnical research program was undertaken in the Donkin-Morien tunnels by Golder Associates in conjunction with CANMET and the Cape Breton Development Corporation (Yuen et al., 1985). The research program included the monitoring of the performance of the TBM and drill and blast drivages, and the study of the thrusting characteristics and rock-interaction of the TBM excavation. The main emphasis of the research program was on the collection of field data which was to be made available in the form of a comprehensive report for the future use of others who might wish to carry out a detailed interpretation and analysis. The information gained from the program was also used during the tunnel drivages to monitor the performance of the installed support and enable changes to be made where deemed appropriate. In addition to the work carried out for the main research program, further displacement monitoring was undertaken during the drivage of Tunnel No. 3. This paper describes the details of the instrumentation program and monitoring techniques adopted during the study. The over-all performance of the instrumentation is also discussed.

Keywords: Rock mechanics, Tunnel boring, Research programs, Instrumentation programs, Donkin-Morien Mine.