New Simplified Method for Analysis of Earth Pressure on the Imperfect Trench Installation Box Culvert

Imperfect trench installation (ITI) is an effective technique to reduce the vertical earth pressure (VEP) acting on the top of a box culvert. Several analytical methods can be found in the literature, but few have considered the friction between the culvert sidewall and adjacent backfill. In this study, a soil–culvert interaction model is proposed to consider the friction on the culvert sidewall. The performance of an ITI box culvert is investigated by model tests and numerical simulations. In addition, a new simplified theoretical method is deduced to calculate the VEP on the ITI box culvert, the friction on the culvert sidewall, and the foundation contact pressure (FCP). The theoretical results are validated by experimental measurements and numerical results. The results indicate that the ITI method significantly increases the friction on the culvert sidewall. Although this method reduces the VEP on the top slab, it has an insignificant effect on the reduction of the FCP as expected. In the design of an ITI box culvert, ignoring the effect of friction on the culvert sidewall probably underestimates the FCP, which will probably induce potential structural hazard to the ITI box culvert.