Monitoring and analysis of a deeply buried culvert covered with expanded polystyrene blocks

The load estimation on deeply buried structures has been a long-standing engineering challenge, where applying the full dead load on the structure is often overly conservative and wasteful. This paper explores the performance of a deeply buried concrete culvert with expanded polystyrene (EPS) blocks placed on its top slab for load reduction. The research included field monitoring via strain gauges, load reduction calculations via a simplified method, and finite element (FE) modeling. Within the FE analysis, various constitutive models for the filling material were assessed, including the Mohr-Coulomb model, the Hardening Soil Model (HSM), as well as a simple elastic model. The results indicated that the soil constitutive model had a minor impact on soil-structure interaction, while the Young's modulus of the filling material significantly influenced the structural response of the culvert top slab. The FE models demonstrated that EPS blocks effectively reduced loads on the culvert, with a notable reduction in the maximum bending moment from 0.07 MNm to 0.04 MNm. The FE models exhibited similar trends to actual measurements in the relationship between cover height and resultant structural strain, although the FE model predictions were significantly lower than the actual measurements. In contrast, the simplified load reduction method was found to be reasonably accurate. The findings of this study offer valuable insights into the efficient and cost-effective design of deeply buried structures, emphasizing the need.