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The weight of the roof is on three vertical posts like that, all with concrete footings (although on of the posts has rotted significantly due to being in contact with the wet clay) and also attached to the house on the upper side. The farthest post was encased up to the wood in the clay.
My neighbour is helping out (he's a retired building engineer) and he reckons we could straighten the beams a bit but I'm not sure on the method he's got in his head.
What's the weight of your roof supported by? The photo does look a little dodgy!
Could you put some wood down and pick up the horizontal beam with telescopic supports?
I wouldn't be overly worried about clay, it just wants to expand. It's not easily washed away unless you have heavy/fast-moving water (cohesive versus non-cohesive).