Development of finite element analysis model for clayey soil-structure interaction analysis under large deformation conditions

Abstract

The purpose of this dissertation is to develop the constitutive equation considering strain-softening and strain rate-dependency that can appropriately simulate the strength change in a clay soil due to large deformation generated during the soil-structure interaction analysis. As for the constitutive equation, the TBSR-VUMAT model is developed by ABAQUS user subroutine VUMAT based on the return mapping algorithm applied to the Tresca failure model. For the large deformation analysis, the finite element analysis technique defined as LDFE (Large Deformed Finite Element)/CEL(Coupled Eulerian-Lagrangian) is applied with the developed model. The developed TBSR-VUMAT model is verified with the preexisting various application cases requiring large deformation analysis of soil-structure interaction problems. First application analysis case, the LDFE/CEL technique, which did not consider the strength change of clay is applied to analyze the stability of the subsea pipeline due to the vertical drop and horizontal drag of the ship anchor causing the large deformation soil problems. Under the stability analysis of the pipeline results, it is then applied for the calculation of the safety height of the rock-berm protection method, one of the protection methods for subsea pipelines. Another application analysis is performed in the Ice-Soil interaction problem, which is an important consideration for the stable operation of subsea pipelines buried in cold region. The Ice-Soil interaction analysis is conducted and compared by applying the developed TBSR-VUMAT model and the LDFE/CEL analysis techniques which did not consider the strain-softening and strain rate-dependency. Ice Gouging analysis model is developed via user subroutine VDLOAD in ABAQUS. The VDLOAD considers the dissipation of the huge ice keel energy by the resistance of the soil. The developed Ice Gouging model analysis results are compared with the other preexisting finite element analyses and the laboratory experiment researches which did not consider the decreasing of the kinetic energy of the ice keel. Finally, the soil and ice keel behaviors in the event of ice gouging are analyzed by applying to the slope ground in cold regions.