Performance of imperfect trench installation box culvert on soft ground

Abstract

The imperfect trench installation (ITI) method is commonly employed to reduce the enormous high backfill load on the box culvert, and its load reduction effectiveness has been widely studied. However, limited research has focused on the behavior of ITI culvert on soft ground. To address this gap, numerical simulations verified by model tests were conducted to investigate the performance of ITI culverts on soft ground and to compare it with that on rigid ground. Key comparison parameters included vertical earth pressure on the culvert top, foundation contact pressure, lateral earth pressure on the sidewall, and settlement above and beneath the culvert. A parametric study was also performed to examine the influence of ground soil parameters, including elastic modulus, friction angle, cohesion and thickness of soft layer, on ITI culvert behavior. Additionally, the impact of improved ground characteristics (i.e., thickness, width and stiffness) was analyzed. The results indicate that soft ground conditions, particularly lower soil stiffness, adversely affect the load reduction performance of ITI method compared to rigid ground. Furthermore, this negative effect can be mitigated by improving the soft ground beneath the culvert in a limited width (e.g., two to three times the culvert width).