Soil–Structure Interaction for Buried Conduits Influenced by the Coupled Effect of the Protective Layer and Trench Installation

Abstract

Understanding the impact of factors on conduit face pressure is crucial for safe design of buried box conduits under embankment loads. This research analyzes the soil–structure interaction coefficient (F parameter) for three sides of the conduits, considering the combined effects of trench and protective layer inclusion. Through physical models and simulations, the study investigates soil arching caused by the trench and soft layer. Parameters such as culvert and trench dimensions, expanded polystyrene (EPS) barrier properties, and soil–conduit and soil–trench contact characteristics are examined. Findings illustrate that the inclusion of geofoam significantly reduces the F value on the top and bottom conduit faces, with the F parameter reaching as low as 0.07 when combined with EPS and a trench. Specific dimension ratios (Bc/Bt=0.2 and Ht/Bc=3.6) result in applied pressure exceeding theoretical pressure (F>1), emphasizing crucial design considerations. Furthermore, EPS thickness has a negligible effect on the F parameter for the top wall but significantly affects sidewall pressure, and optimal EPS dimensions (tg/Bc=0.5 and Bg/Bc=1.5) substantially mitigate the sidewall pressure. Increasing soil–trench contact friction considerably reduces the interaction coefficient, but no further reduction occurs beyond 33°.