Plane Failure Plane Failure 08/15/26 “What causes a mound of soil to collapse down a plane surface?” Slope collapse is a serious problem that people need to contend with. When a slope failure happens down a relatively flat planar surface, it’s labelled a Plane Failure. Share this: Share on X (Opens in new window) X Share on Facebook (Opens in new window) Facebook Like Loading... Earth/Climate scienceEngineeringUrban Systems