Trans RINA, Vol 154, Part C1, Intl J Marine Design, Jan - Jun 2012


NWT with 39% of mining employees being of aboriginal origin and an overall average wage 44% higher than similar jobs in other areas of Canada [5]. The future prospects for this comparatively young industry also look promising. The Diavik diamond mine is projected to remain operational until 2023 and the Snap Lake mine 2022-2024 and


several new mining projects are


advancing towards the operational stage such as Gahcho Kue in the NWT. In 2006, the country's then Prime Minister, Stephen Harper, stated the prediction that "Diamonds will bring over C$70 billion to the Canadian economy over the next 25 years" [8]


1.1 DRIVING ON THE TCWR


For the 480 km of the Tibbitt to Contwoyto Winter Road (TCWR) which passes over frozen lakes, safety is the top priority of the joint venture behind the road and the record is good: In 2007, out of nearly 11,000 truck loads, there were only nine incidents resulting in only one minor injury [3] a testimony to the effective education and enforcement of safety. Every year the drivers who intend


to operate on the TCWR attend briefings


explaining the importance of these rules and what can happen if they don't follow them. One of the most important things stressed at these meetings is that they follow the speed limits at all times. Exceeding the speed limit can have serious consequences, especially on the ice. How the ice behaves underneath the vehicles using the road is a critical factor.


The Ice bends underneath each vehicle creating a shallow bowl shaped depression the ice returns to its original position once the vehicle has moved on, this creates a moving depression in the ice beneath each vehicle, which in turn, creates a pressure wave in the water underneath the ice. For


slower moving vehicles this


depression/pressure wave moves along with the vehicle. Whereas, with faster vehicles the depression shortens and deepens and can lag behind the vehicle.


The maximum speed allowed for loaded vehicles on the ice is 25 km/h (JVTC Winter Road 2010); above this the vehicle is in danger of reaching critical speed. At the critical speed the depression reaches its minimum length and maximum depth, two waves are created in the ice, one ahead and a second behind the vehicle, and the stresses in the ice reach a maximum significantly increasing the likelihood of failure. The ice sheet may crack and weaken. Drivers following may be at risk from weakened ice which can cause blowouts in surface of the ice


The TCWR is 30-50 metres wide on the lake ice, allowing sufficient distance between vehicles passing in opposite directions. Trucks are usually dispatched in groups of three with about 20 minutes between each convoy and approximately 500 metres between each truck in the group to avoid overlapping loading on the ice. The weight of each individual load, the distance it needs


to be taken and the experience of the driver are all taken into account when planning the convoys to ensure that the ice is not overstressed and that the convoy is led by an experienced driver. The majority of the TCWR runs over frozen lakes but 15% of the route is comprised of land crossings between the lakes known as portages [3]. These crossings are generally shorter than 1 km but can be longer. Trees are felled where necessary to create a route through which the vehicles can pass and the portages are deliberately flooded with a mixture of snow and water, which freezes quickly creating an almost seamless transition between the lake ice and the land. The speed limit on portages is 30 km/h and must be reduced to 10 km/h entering and exiting the portage [3].


Driving on the portages can often be more hazardous than the lake ice. The width of the road is generally reduced from 50m on the ice to around 15m on land and whereas the lake ice is flat, the portages have a gradient. The inclines


onto and off of the portages can be


extremely ice and slippery and cannot be sanded as the sand heats up from the sun and damages the approaches. The approaches are dog-legged to slow the trucks and dissipate the waves under the roadway prior to the truck reaching the shore so there is no possible way for a truck to gain momentum prior to reaching the icy inclines [9].


Portage 25 known as "Charlie's Hill" is one the steepest on


the TCWR and drivers must maintain their


momentum from leaving the ice road to the top of the hill or they risk losing traction. Trucks have got stuck on the hill and jack-knifed, blocking the route. This causes a backlog of trucks that are forced to stop on the ice until the blockage is cleared. This hill is not particularly steep in the region of a 4 - 5% grade but it is long enough to make for a hard pull since a truck cannot take a run at it. The entire road surface is ice and cannot be sanded or gravelled without damaging the surface and similarly, tire chains are also not allowed [9]. The portage approaches are designed with a dogleg curve to help dissipate the pressure waves under the ice. This is to avoid the pressure building up at


the point the road


leaves the lake ice that could rupture the ice or cause a blow out. This presents a challenge to drivers who cannot build up much momentum to help them overcome the incline on leaving the lake.


2. INDUSTRIAL DESIGN


Industrial Design is about creating and developing design concepts and specifications that optimise the function, value and aesthetics of products for the mutual benefit of both the end user and the design client. Industrial designers develop these concepts


and specifications


through research, analysis and synthesis of information determined by the requirements of the client design brief. They are


trained to communicate design


recommendations through drawings, models and verbal descriptions. Industrial design activities involve working


C-2


©2012: The Royal Institution of Naval Architects


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