The elephant foot bulging deformation develops with the increasing stress of the rigid wall, which is caused by the uplift of the tank bottom and the impaction between the tank bottom and the foundation.

• 因罐底提离导致的罐底与基础反复撞击加大了作用在罐壁上的应力，使罐壁底部“象足”变形不断发展，最终导致罐壁撕裂。