Numerical Study of Laterally Loaded Batter Pile Groups with the Application of Anisotropic Modified Cam-Clay Model

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Zhang, Yida
Group batter pile foundation; Sub-stepping; Anisotropic modified cam clay; FEM; lateral load; p-multiplier; FB-MultiPier
thesis / dissertation description
This study presents a series of numerical studies of laterally loaded batter pile groups based on data of the full-scale lateral load test on M19 eastbound pier foundation of the new I-10 Twin Span Bridge, Louisiana. The numerical studies include several continuum-based 3D finite element analyses on batter/vertical pile/pile groups and a FB-MultiPier analysis of the pile foundation. The Anisotropic Modified Cam Clay Model, has been implemented into UMAT and applied for describing clay behavior in all FE models. The explicit substepping scheme with modified Euler algorithm is selected to implement the model in ABAQUS software. The resultant UMAT shows good accuracy compared to the ABAQUS in-built Modified Cam Clay model. Also it exhibits wonderful computational stability and efficiency in the pile group analyses, which greatly accelerated the whole research processes. The results of FE analyses were compared with the measured field data from lateral load test and those predicted by FB-MultiPier. All of them showing good agreement on lateral deformation profiles and bending moment profiles. The comparison of the lateral deflection, bending moment, soil resistance and lateral/ vertical load distributions between different spacing batter/ vertical pile groups and single isolated pile illustrate that small spacing and the vertical piles will produce intensified group effect. The concept of “trapezoidal zone” is firstly proposed to explain the axial load distribution pattern of batter pile group foundation. An additional coupled pore fluid diffusion and stress analysis on a single pile model demonstrated that the resultant excessive pore pressure caused by lateral loads has limited influence on the result of FE analyses.