ABSTRACT
The performance limit of ring stability is instability. Ring instability is a spontaneous deformation that progresses toward inversion (reversal of curvature). At worst, instability is ring collapse. Buried pipes can invert only if the ring deflects and the soil slips at the same time. Instability of buried pipes is analyzed as a soil-structure interaction. The stiffness of the ring resists inversion. Soil supports the ring by holding it in a stable (near circular) shape. Soil resists inversion of the ring.
