Here is a satellite image of the Brunt Iceshelf where Halley is located - if you need reminding where Halley is on a larger scale then I have put the globe view below. The Brunt iceshelf is about 50km wide and a 100km long, it is made of freshwater ice of about 200m thickness floating on the sea. If you made a 1 to million scale model it would be about the same size and thickness as a playing card. There has been a permanently manned research station here since 1956.
One of the difficulties of building on a ice shelf is that the surface
continuously accumulates. If you put something down on the Brunt iceshelf
then a year later it will be a metre under the snow surface, another
year later it will be another metre deeper and so on. This is exactly
what happened to the first research station built here, it was buried
and effectively crushed by the weight of the ice and snow above it. A
series of research stations was built over the years, and despite being
increasingly strong they all suffered the same fate - the weight of the
ice and snow caused great crushing damage and it was difficult to
operate a deeply buried station. In 1990 BAS built the 5th reincarnation
of the Halley research station but on legs so that it kept clear of the
ever increasing snow. Every year the station would be jacked up (the
legs extended upwards and the whole station moved up the legs) to keep
it at the same height above the snow. Here is what the main platform
looked like in the 2001/2 season which is when I last visited Halley.
The second major difficulty of building on an iceshelf is that the ice flows, Halley V (as the 5th Halley is known) is moving closer to the iceberg calving point at about 350m per year. In fact it is already very close to a point known to be open water in 1958 (the earliest reliable ice edge survey), and this is why we need to build a new station, despite Halley V being in good condition. Once the construction of the new station started we stopped raising Halley V above the snow each year, and this is what it looks like now.