They are only strong at specific points, namely the corners and to a lesser extent, the edges. If you have a load on top, or an impact on the sides, they deform

They are only strong at specific points, namely the corners and to a lesser extent, the edges. If you have a load on top, or an impact on the sides, they deform easily and that can cause structural collapse. In situations where people bury the containers, they often have to weld in additional squarestock steel pillars and ceiling joists to improve the structural integrity of the roof, and the pillars often add needed support to the walls that face substantial forces from the weight of the earth