February 2009

Engineering Exchange

Distinguished at any depth

By B. Sundararajan

Shaft sinking at Xstrata Nickel’s Nickel Rim South project in Sudbury, Ontario

The mine contracting and engineering consultancy Cementation has been recognized in recent years as the most active shaft sinking contractor in North America, both in terms of volume of work as well as in the complexity and technical difficulty of projects undertaken. Cementation has played critical mine building, engineering and shaft sinking roles in a number of noteworthy projects — the Lupin mine in the Arctic, the Picadilly project in Sussex, New Brunswick, the Red Lake mine in northwest Ontario (widely recognized as the richest gold mine in the world in terms of grade), the Diavik diamond mine in the Arctic, the Resolution mine in Superior, Arizona, and the Kidd mine in Timmins, Ontario.

Roy Slack, president of Cementation Canada, described the approach that enables Cementation to successfully deal with the complex engineering challenges posed by these projects as a “best for project philosophy.” This philosophy allows them to continuously look for ways to help the client and the project. “As the contractor, we wanted the ability to add value at the concept and feasibility stages,” said Slack. With this approach, Cementation can develop fast-track construction techniques and more accurate and realistic schedules and budgets.

Shaft sinking, in general, requires a higher degree of technical support and innovation than other mine development work. Sinking through water-bearing strata carries additional challenges. In these cases, the shaft lining must be carefully shored and sealed and any ingress water must be handled as well.

Slack explained some of the challenges with reference to the Kidd, Diavik and Resolution mines. In the case of the Kidd mine, Cementation began by working with the owner on the base case building schedule. By doing the headworks and the first section of the shaft concurrently, they were, quite remarkably, able to shave about a year off the schedule. The main challenges revolved around the sinking of a 7.63-metre concrete winze (internal) shaft underground. “The thing about a winze is that all of the same equipment and facilities that you would use on the surface now have to be excavated and constructed in rock,” explained Slack. “Of course you are doing it at depth, so there are geotechnical challenges. There are all the logistics of ventilation and power distribution. All those things are complicated enough on surface, but the complexity is multiplied underground.”

At Kidd, it was the depth of the shaft that came into play. Because it extended 3,220 metres below the surface and had a completed winze depth of 1,906 metres, heat and ventilation were highly problematic. Slack said that having both the headworks and the first section of the shaft done at the same time doubled the amount of engineering required at the front end. That shaft was the deepest in the world outside South Africa. The logistics of moving all the equipment underground — the grounded depth, the heat and ventilation — were all major issues to deal with. “Anytime we sink a shaft or go to depths in a mine, the geothermal gradient is a factor,” Slack explained. “Every metre of depth adds a little bit of temperature. With Kidd, initially it wasn’t a problem, but when we got to lower levels, we had to use cooling systems and staged work to make the conditions acceptable.”

“With Diavik, initially we were dealing with permafrost,” Slack said, recalling another challenging undertaking. “On the approach to the kimberlite pipe, the ground changes, and there are other issues to deal with. There are certain methods of coping with these ground and water issues, which are not necessarily innovative. However, to ensure the integrity of the excavations, particularly close attention had to be paid to quality control to ensure the right things were done at all times.” Foreseeing another challenge in the offing, Slack added that at the Resolution mine, as they go deeper, heat is going to be more of an issue than at Kidd. “Each one has its unique challenges,” he added.

Cementation adheres to high safety standards. One of the projects they are quite proud of is the Nickel Rim South twin shaft project. “We just sank two shafts at Nickel Rim with no lost time injuries,” Slack said proudly. Cementation has now been recognized for three years in a row by Mediacorp Canada as one of the top employers in Canada and, most recently, by the Financial Post as one of the top ten employers in Canada. The company seeks to be an employer of choice and has been continuously focused on that.

With such focus on its people, adherence to the highest safety standards and industry-standard benchmarks for quality and innovation, Cementation has definitely cemented its reputation and legacy as one of North America’s finest mining contracting and consulting organizations.

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