Why does Martin bury himself under soil?

When he wakes in the morning at the lake house, he goes out, takes a shovel, makes a hole in the ground, lies down in it and buries himself under chunks of soil.

Is there a special meaning to that scene? Did he do it because he felt guilty about the night before and wanted to 'atone' for it somehow? Did it symbolise the old him dying and the 'family man' version of him rising up? Any thoughts?