This thesis has undertaken extensive field investigation into the response of helical culverts during incremental backfilling and under legal live loads on sinusoidal profile and ribbed profile helical culverts. Deformation, earth pressure and steel strains were measured. The strains were decomposed into hoop force and bending moment. Force-deflection tests were undertaken to determine the effective section properties that took into account the cold-formed section properties and irregularities from rolling during manufacture. High lateral earth pressures were measured during backfilling. A model was developed to demonstrate the formation of those pressures that approach the passive state. This has important implications for the design of buried structures and retaining walls. The response of helical culverts to legal live loads was examined. The effect of vehicle offset and time-dependent effects were considered. Dynamic load allowance was determined. The thesis also examined collapse mechanisms of helical culverts. It is essential that installers fully understand the response during backfilling A simplified design method has been developed which incorporates the maximum crown moment during backfilling. This is the critical load case. The results of the field measurements and numerical modelling have been compared with published literature.