Cat Gillies, Structural Engineer, writes about working at Halley
As Structural Engineer, I am responsible for maintaining the building structure throughout the winter. Due to the constant movement of the ice shelf and the snow accumulation around the buildings, the legs of the building suffer differential movements. The steelwork itself can accommodate this but the sealed wooden superstructures in which we live and work would eventually be damaged by support from an uneven platform. Each month throughout the winter, I carry out a survey of the legs relative to one another and then, along with the willing assistance from a fellow winterer, manually jack the beams to keep within the desired tolerances. During the summer season the platforms are raised using electric motors by around 1 m, depending on the previous year's snow accumulation, to maintain the buildings at a height of 5 m above the snow surface.
As the wind blows, the platforms sway. To reduce this sway to a comfortable level, tension guys are anchored at each side of the steel frames. The tension in these guys is monitored by strain gauges and data recorded at a computer terminal. It is necessary to keep these guys at a desired load as vibrations carry into the building when they are too tight and sway levels increase if they are slack.
Snow accumulates around anything on the snow surface which is the reason for the elevation of the buildings. Previous buildings at Halley have been built at snow level and allowed to bury. The advantages and disadvantages of above and below ground structures are numerous although it is certainly an advantage to have windows in the accommodation. Although the buildings are elevated, wind tails' still form to the up- and down-wind side of the platform which cause the legs to try to incline. The inclinations increase over a period of years and at a cut-off point the legs are then offset to straighten them. In order to monitor the effects of the wind tails on the building legs, a set of glacier poles are used as survey points to plot the profiles of the snow around the buildings with reference to the general snow accumulation and wind speeds over time.
The ground' conditions make Halley V an extremely interesting structure to work with, and I hope to apply engineering theory to some of the glaciological sciences already studied around the ice shelf. The area of concern and the time-scales relevant to each discipline differ greatly, but hopefully the gap can be bridged with the investigation into the action of the structures here at Halley V.