Our tunnel is 14m x 7m, Northern Polytunnels with extra hefty tube thickness and diameter, and has been sitting on a very windy hilltop for the past 15 years or thereabouts. It has base tubes set in hefty concrete dollies, every stabilising storm saver inside, such as triangular corner braces and braces to the ridge pole, plus crop bars at every hoop. We have the thickest polythene cover available too, wooden base rails, wooden and corrugated poly-whatever-it-is doors and louvres and a 2m windbreak fence set back about 10m all the way round (which forms my veggie patch.
About 9 months after we put it up the cover tore at the upwind side in an 80mph gale. My OH swung from the crop bars and slit the polythene right down the middle to release it before it could destroy the whole tunnel. The force of the wind on so much sheeting is enormous - think sailing vessels. We found that ours had twisted the coachbolts holding the base rail to the hoops to about 30 or 40 degrees. the problem was that we had wound the polythene the wrong way around the slats used to attach the cover to the base rails so this made it vulnerable to a southerly gale which hit it longside on (the correct way seems counter intuitive to me).
Since then we have had no problems with the cover and have had to change it only once in all that time due to old age not tearing.
However, in every side-on gale (and we have a few, even up to 100mph once) the whole structure flexes dramatically, from side to side. My greenhouse is inside the tunnel and the apex comes to within a foot or so of the polythene. One year the cover was torn by rubbing against the sharp corner of the greenhouse roof. So that is how much flexion there can be at the height of the storm with no major damage. Our main precaution is to check every bolt holding the structure together both before and after a storm - in the early days the bolt heads would get shaken and start to undo but that happens less now they have bedded in.
I don't think a dug-in cover would last long up here, but I think the metal parts of the tunnel structure are designed to flex. The wind pressure from the sides can apparently cause the flimsier structures to crumple in windy areas, hence our 'overkill' precautions.