Seismic Behavior of Box-Shaped Culverts Buried in Cohesionless Soils

A numerical modeling study was carried out to investigate the dynamic behavior and lateral earth pressures on box-shaped culverts buried in dry cohesionless soils. Two dimensional plane strain finite difference models of 4m-high prototype box culverts having different wall flexibilities were analyzed using FLAC-2D Finite Difference Code. Within the analyses, uniaxial input motions composed of harmonic excitations with amplitudes of 0.25 g and 0.40 g and frequencies of 2 to 15 Hz were applied to the numerical models. Box culvert sections with different wall thicknesses were analyzed to investigate the effect of relative flexibility on the dynamic response. Shear strains, horizontal accelerations, wall deformations, and lateral dynamic earth pressures at various points on the culvert were monitored. Racking deformations were calculated from displacement data obtained from the analyses. Results of the numerical analyses were validated with those of the centrifuge tests performed under 40-g centrifugal acceleration. Racking deformations of the analyzed culvert models are in good agreement with the test data. Racking curves for culverts having different flexibilities were estimated based on numerical modeling results. Good agreement exists between the actual data and those predicted with the finite difference method. Dynamic lateral pressures acting on the side walls increase as the wall flexibility ratio decreases. For the range of excitation characteristics, dynamic force on the sidewalls of the box culvert may reach up to 2.8 times the at-rest lateral stress for the stiff prototype.