FEM With Curved Hexahedron Element and Application on Tunnel Integrated Grounding System in High-Speed Railway

Abstract

With finite element method (FEM), cuboid elements (or tetrahedron elements) are often used in the traditional grounding analysis. In the irregular boundary, smaller and denser elements are usually applied to approximate the real boundary. However, this increases the number of elements in the boundary, leading to an increase in computation time. In order to introduce FEM into tunnel integrated grounding system (IGS) in high-speed railway better, a curved hexahedron element is proposed for tunnel structure. In this paper, the stiffness matrix of curved hexahedral element in space is first derived based on coordinate transformation. Two different stiffness matrices are compared in the condition that the structure of curved hexahedron element is highly similar to that of cuboid element. Later, the number of required elements according to the proposed method is compared with that of the traditional one on the basis of meeting same accuracy requirement. Finally, the results of the proposed method are compared with those of current distribution, electromagnetic fields, grounding and soil structure analysis (CDEGS). Through the above-mentioned three comparison schemes, the curved hexahedron element model is verified by its precision and applicability. From this, the distribution of the electromagnetic field inside the tunnel IGS is obtained.