Greater Sudbury Rock Tunnel is 75% CompleteGreater Sudbury is a city in Northern Ontario, Canada, created in 2001 by amalgamating the cities and towns of the former Regional Municipality of Sudbury, along with several previously unincorporated geographic townships. The CAD31.1 million south end rock tunnel is the largest municipal construction project since amalgamation. Visit www.greatersudbury.caOn 23rd January, 2008, general contractor McNally Construction achieved an intersection of two tunnels, advancing from the southeast and northwest (see map). The joining marked a completed distance of about 3,900 metres, or 60%, of the project's final 6,496 metres. As of 31st March, 4,894 metres of tunnel has been excavated and 1,567 metres remains to be excavated. This corresponds to an advance rate of 75%. The biggest challenge with this job to date has been finding, training and maintaining the labour force. Consulting engineer for the south end rock tunnel is Dennis Consultants. Visit www.mcnallycorp.comConstruction has been ongoing since August 2005 from a ramp system that descends from surface to a final depth of approximately 25 metres. A second underground access point was constructed in November 2006. When finished, the project will add 6.5 kilometres of 1.5 m-wide x 2.1 m-high rock tunnel, three access shafts and nine concrete drop structures to the city's existing network of sewage collection tunnels.Work is now proceeding on the remaining branches of the underground rock tunnel. The extensions are southeast to the intersection of Green Avenue and Highway 69, east to the intersection of Loach's Road and Oriole Drive, west along Bouchard Street to the existing rock tunnel near Southview Drive and northeast to Walford Road. The south end rock tunnel is scheduled to be complete by 31st December. The expansion will provide additional capacity for future growth in the south end of the city and it will mitigate environmental concerns associated with limited sanitary sewer capacity. Once on line, the sewage collection tunnel will eliminate the need for six existing sewage lift stations. View pictures here. Click ca/27. GeologyThe tunnel lies in metamorphosed Precambrian sedimentary rocks, with the majority of the tunnel falling in the Mississauga formation which consists of quartzite, arkose and greywacke. Generally, the uni-axial compressive strength of the rock ranges from 100 to 250 MPa, with the majority of the rock falling in the higher range of UCS values. The tunnel typically runs about 25 metres below ground surface, with the least cover at 12 metres. Minimum rock cover for the tunnel is anticipated to be approximately five metres. Rock quality assessments based on GBR (Geotechnical Baseline Report) show about 50% of the tunnel having a Q value of greater than 40 (requiring little support), 40% having a Q value between 4 and 40 (requiring pattern bolting), and about 10% having a Q rating of less than 4 (requiring pattern bolting, mesh and shotcrete). Drill and blastThe method used is drill and blast. McNally Construction is using jacklegs and steel provided by Boart Longyear. The button and reamer bits are B & J Industry supplies. The explosives are AP detonator sensitive emulsions, Unimax dynamite sticks and ANFO powder from Dyno Nobel. There are eight headings. Visit www.boartlongyear.com and www.dynonobel.comYale siteHeadings were developed in both directions from the shaft at a width of four metres to allow for a staging/switching area for the tunnel operations. This section of tunnel was driven utilizing jacklegs, an Eimco 630 overshot mucker, and a 1.14 m scoop. Upon completion of this section, rail was laid in preparation for mining of three separate headings. The shaft was separated into two compartments, one for mucking and the other containing the man way and utilities. All three headings are being driven utilizing jacklegs, Eimco 12B overshot muckers, 5.5 tonne Clayton battery locomotives, and 2.18 cu m side dump muck cars. Visit www.tridentsa.co.za and www.claytonequipment.co.ukTypical tunnel rounds are 1.8 m in length and require thirty-eight 32 mm production holes and three 64 mm "reamed" relief holes. Holes are loaded with ANFO, and perimeter holes are loaded and traced with primer cord to produce a smooth wall, "half barrel". Nonel "easy drifters" are used for caps, and the round is initiated electrically from the station area.All headings are running an exhaust system which allows the headings to operate independently. Ventilation is exhausted from each heading to surface utilizing 7.5 HP fans. Utilizing an exhaust system allows each heading to blast independently, as all contaminated air is sucked through the vent line and discharged on surface. Two 750 CFM compressors coupled to a receiver tank, located on surface, are used to supply air to the tunnel.In the shaft, a 30 cubic metre box was installed below grade to receive muck. An air cylinder is mounted in the wall of the shaft that is utilized for dumping the cars. A 9570 Northwest Crane equipped with a 2.28 m clam is then used to hoist the muck to the surface. All mucking is performed with a camera system which allows the operator to clam without a signalman. Shaft access is controlled by a light system operated by the crane operator. Burwash siteFrom the bottom of the ramp, all three headings were developed utilizing the 2.28 m scoop and jacklegs, to sufficient length to allow for rail installation. A sump and remuck area was also excavated at this time. All headings are mined using jacklegs, Eimco 12B muckers, 5.5 tonne Clayton battery locomotives and 10.05 m Hägglund cars. Typical tunnel rounds are the same as the Yale site, although mining from this location has encountered more water which has necessitated the use of packaged emulsion products in place of ANFO.All air for ventilation is blown down the shaft. From the shaft, about two thirds of the air volume flows directly up the ramp. Each heading is equipped with an exhaust fan setup that draws fresh air from the station area to each heading and deposits it back into the ramp. This setup ensures that the station area is not contaminated when blasting occurs, allowing the headings to work independently. Compressed air is provided on surface utilizing two 750 CFM and one 600 CFM compressors coupled to a receiver tank.Hägglund cars are discharged into the remuck area, where the 2.28 m scoop loads and hauls the shot rock to the surface. Breakthrough connecting the South tunnel at Yale and the North tunnel at Burwash in January 2008 Green siteBoth headings were developed from the bottom of the ramp utilizing a 0.45 m scoop and jacklegs at a width of four metres to allow for a staging/switching area. Upon completion, rail and switches were installed, along with the sump/remuck box and dump cylinder. Fans are set up exhausting from each heading, and a 600 CFM compressor coupled to a receiver is supplying air.The shaft is divided and a camera system has been set up. A 108 Link Belt equipped with a 0.7 m bucket is being used to muck. This heading is also using the same type of locomotives and mucking machines as Yale. Visit www.linkbelt.comSupportWhen needed, support consists of 1.22 m and 1.83 m forged head rebar bolts with plates, fast and slow resin bolts, and roof straps, all supplied by Mansour, wire mesh from DSI, steel arches supplied by American Commercial, MS-D3 mining shotcrete supplied by King Packaged Materials Company and ChemGrout shotcrete pumps. Visit www.mansourgroupinc.com, www.dsigroundsupport.com or www.dsi-underground.com, www.americancommercial.com, www.kpmindustries.com and www.chemgrout.com 16/08.