Book excerpt: The general objective of the investigation was to study experimentally the behavior to failure of flexible, horizontally oriented cylinders buried at various depths in dense, dry sand and subjected to either static or dynamic surface overpressures. Static and dynamic tests were conducted on 33 different cylinders, fabricated of high-yield-strength aluminum. Results indicated that collapse of the cylinders occurred while the strains in the cylinder walls were still in the elastic range. The cylinders buried at the shallow depths (zero to one-half cylinder diameter above the crown) collapsed by a catastrophic snap-through or caving of the crown. For the cylinders buried at depths of three-quarters to two cylinder diameters above the crown, the mode of collapse was an instantaneous elastic buckle that occurred at the spring line or invert of the cylinder. The collapse mode of the cylinders under dynamic overpressure was similar to that of the cylinders collapsing under static overpressure. The results of the investigation verified the applicability of an equation for predicting the static collapse overpressure for smooth-walled, horizontally oriented, buried cylindrical structures and entranceways. The hoop-compression theory was found to be applicable for analyzing the structural design to determine if the cylinder would collapse in the elastic range. (Author).