EVALUATION OF STRESS OF BOX CULVERT FOR AGRICULTURAL DAM

Abstract

The current design for culverts is based on a two-dimensional analysis and only addresses the internal forces of the culvert members in the cross-section. The stress of a culvert in the direction of the culvert axis has not been given much attention; thus, there are no specific guidelines or provisions for it in the current standards. In the case of a culvert under a fill-dam placed on a soft foundation, the differences in settlement along the culvert axis may cause bending stress or tensile stress at the bottom of the culvert in the culvert axis direction. When this stress is beyond the capacity of the culvert material, excessive deformation and cracks in the culvert can occur. In the present study, this issue was explored through both two-dimensional (2D) and three-dimensional (3D) finite element methods (FEMs). This study reveals that the 2D plane strain FEM, although it can model with soil-structure interaction, it is incapable of recognizing stress along the culvert axis. In contrast, the 2D plane strain FEM can determine that stress but can not consider the influence of soilstructure interaction. Meanwhile, the 3D FEM provides excellent soil-structure interaction and considers the actual shape of the structures. Based on the results, it was shown that the 2D FEM is unreliable in its assessment of the tensile stress along the culvert axis compared to the 3D FEM when the box culvert was placed on a soft, deep foundation. The findings also revealed that when the foundation was soft (the stiffness of the foundation was low), other parameters such as the height of the dam and the depth of the foundation had a significant effect on the tensile stress at the bottom of the box culvert in the direction of the culvert axis.