Cold calling

Ice is a subject close to the heart of Dr Dougal Goodman — and understanding its mechanical properties is becoming increasingly important, he told Jon Excell.

The polar regions present engineers working there with a series of unique challenges. It’s sometimes hard enough simply to survive in the extreme cold and perpetual darkness of these environments, let alone see through a successful engineering task.

But while the biggest draw for researchers is often the opportunity offered by such an abundance of ice, the difficulties created by this shifting, cracking, treacherous material are also one of the biggest headaches.

Fortunately, today’s engineers and project leaders are equipped with an understanding of ice that is having an ever greater impact on the way in which they work in some of the planet’s harshest environments.

This is thanks to people like Dr Dougal Goodman, director of The Foundation for Science and Technology, and one of the world’s foremost experts on the mechanical properties of ice.

From his Cambridge University PhD, to time working for BP and the five years he spent in his previous position as deputy director of the British Antarctic Survey, much of Goodman’s career has been devoted to trying to better understand the properties of a material that covers almost 10 per cent of the surface of our planet.

His role today doesn’t afford him as many opportunities to indulge his polar passion — he’s far too busy fulfilling the foundation’s remit of promoting debate over the major scientific and engineering issues of our time — but Goodman’s enthusiasm for the Earth’s cold, icy places remains.

‘Understanding the properties of ice is fundamental to engineering projects in the cold parts of the world,’ he said. ‘Providing you understand its properties you can make use of it like any other engineering material — engineers should look at ice not as a peculiar material, but think about it in the same way they think about plastic or concrete or steel so that they take its characteristics into account in design.’

He said that the difficulty of working with ice is largely down to its unusual creep and fracture properties. Creep is defined as the progressive deformation of a material under constant stress so that it appears to flow like an extremely viscous fluid. These are the reasons why it is possible for ice-breaking ships to plough through 1m-thick ice without sustaining damage.

Goodman explained that on a relative scale ice is far more creep resistant and has a lower fracture toughness than any other engineering material. When a crack develops through a material there’s a deformation zone just ahead of the crack tip which is dependent on the creep properties of the material. The low creep rate of ice means that this deformation zone is very small, and therefore the energy loss in the material as the crack propagates is very low.

This leads to ice having a very low fracture toughness — in other words it is easily broken, a property that makes it a highly challenging engineering material.

Goodman relates this property to the problems involved in the construction of ice roads, where low fracture toughness can often lead to catastrophe.

‘When constructing an ice road, you want to know what the maximum load is that the road will take,’ he explained. ‘This is a dynamic problem because as a vehicle moves along, the ice vibrates in a coupled way with the vehicle so the loading of the structure is dependent on the speed at which it is travelling.’

Though partly dependent on the thickness of the ice, the speed at which this coupling occurs is often at around 20mph — a speed at which tentative drivers are likely to progress along an ice road.

Indeed, according to Goodman, such misplaced caution frequently leads to cars crashing through ice roads, such as those built across Canadian lakes in the winter.

Similar challenges are presented by the ice runways used by military forces and aircraft landing at remote polar research bases.

Goodman explained that as aircraft slow down on these runways and pass through this critical coupling speed, pilots are often confronted with the unnerving sight of a potentially disastrous crack forming and propagating down the runway ahead of the aircraft.

While there are numerous scientific and engineering projects underway that require a sound understanding of the engineering properties of ice, the biggest area is undoubtedly the oil and gas industry.

During his time at BP in the 1980s, Goodman led a programme involved in estimating the cost of building offshore structures in areas such as Alaska. He carried out a great deal of work and research into estimating and predicting the loads imparted on offshore structures by the movement of ice.

When oil prices fell in the 1990s the offshore industry’s interest in such areas waned, but today, with the security of the world’s oil supply firmly under the spotlight, the oil industry is eyeing the polar regions with renewed interest.

Goodman cites a presentation given by Helge Lund, chief executive of oil and gas supplier Statoil, at a recent meeting organised by The Foundation for Science and Technology.

‘This meeting focused on a joint initiative between the UK and Norway to develop new acreage in the North Sea,’ he said. ‘It was clear from presentations made by Statoil that it is interested in moving further north and round the corner into the Barents Sea. If it does this, at some point ice loading will become an important issue.’

The properties of ice will also have a huge bearing on many of the big pipeline projects that are currently being planned for the Russian arctic regions. Here, the biggest challenges are raised by permafrost — the permanently frozen matrix of ice and soil that forms a large part of the ground in the arctic regions.

‘Designing buildings or pipeline supports that will not melt the permafrost is an important element of arctic design,’ said Goodman.

He explained that BP’s trans-Alaska pipeline, which connects Prudhoe Bay to Valdez, is supported along part of its length by piles that act as refrigeration units and prevent heat from being conducted down into the permafrost. If this melted the pile would move and that would be unsafe for the pipeline.

However, while many of the engineering challenges presented by the permafrost have already been surmounted by BP’s existing pipeline, Goodman warned that climate change means that engineers must be prepared to adapt to a changing environment.

‘There is a concern that because of climate change the position of latitude of the permafrost line is moving further north — what is permafrost now may not be in 30 years’ time — and designing support structures to anticipate that change is very tricky. But engineers have to get on with it and design to anticipate change.’

While Goodman today turns his attention to a variety of disparate science and engineering issues, from questions over nuclear power to debate on drugs, alcohol and health, he hasn’t completely turned away from the world of ice and snow Indeed, one of the many important areas under the foundation’s spotlight is arctic development in the oil industry and the opportunities this offers the UK.

‘The UK is very involved in arctic development — the many opportunities within the oil industry mean that ice is a big concern.’

Today, Goodman is more likely to be found in the Lords than the South Pole, but he talks fondly of revisiting his old scientific haunts on family holidays. It is reassuring that someone who could well influence decisions of dire economic and environmental import still holds a passion and enthusiasm for the polar regions — and an engineer’s understanding of the fundamentals.