Calculation of large-diameter GFRP pipe culvert deformation under thick cover soil based on two-parameter foundation model

ObjectiveThis study investigates the deformation of large-diameter glass fiber reinforced plastic (GFRP) pipe culverts under thick cover soil in highway engineering. It aims to derive accurate theoretical deformation calculation values.MethodFirst, the two-parameter foundation model considering soil shear was introduced as the interaction model between pipe and soil. The modified foundation reaction coefficient proposed by Selvadurai was used to replace the passive earth pressure coefficient of soil in Iowa Formula. Second, on the basis of this model, the vertical earth pressure calculation formula applicable to GFRP pipe culverts was derived by utilizing the settlement difference of soil columns inside and outside the top plane of pipe culvert. This formula was substituted into Iowa Formula, and the modified deformation calculation formula for GFRP pipe culverts was obtained. Finally, the laboratory model test and finite element simulation were carried out without any unloading measures. The proposed formula, Iowa Formula, test result and finite element simulation result were compared and verified.ResultIn confined conditions, the calculated values derived from the modified deformation calculation formula were closer to the test values and simulation values than those from the unmodified Iowa Formula. In unconfined conditions, the deformation values calculated with the modified deformation calculation formula were more consistent with simulation result than those calculated with the unmodified Iowa Formula. The modified deformation calculation formula was compared with the numerical simulation result after unloading measures were applied; the error between them was slightly larger than that in the case without unloading measures. However, the overall trend varying with filling height is basically the same as that in the case without unloading measures.ConclusionThe findings verify the correctness of the modified formula for large-diameter GFRP pipe culverts under thick cover soil without unloading measures, as well as prove the rationality and feasibility of the modified formula when unloading measures are applied.