Abstract:

Sequential limit analysis (SLA) has been recently introduced into geotechnical engineering, in which a large-deformation problem is discretized into a sequence of small-deformation finite element limit analyses, and has been successfully used for the analysis of soil-structure interactions in undrained soft clay under plane strain condition. SLA method possesses high computational efficiency and numerical stability, and its calculation error can be real-time evaluated based on the deviation between upper-bound and lower-bound solutions. In this paper, the existing plane strain SLA method is extended to be suitable for axisymmetric problems such as vertical loading behavior of spherical probe instruments, pipe piles and spudcans. A new version of SLA is developed on the numerical platform OPTUM to broaden its usage. Additionally, the updating method of the model geometry based on velocity fields obtained from upper-bound solution in the original SLA is improved, so that it can adapt to more extreme soil deformation. A series of classical plastic solution cases and model tests are then used to validate the accuracy and effectiveness of the extended SLA method. It proves that this method can be used to simulate large displacement / deformation problems such as the vertical and lateral interactions between undrained clay and facilities such as foundation, penetration equipment and pipelines.

Key words: large deformation analysis, limit analysis, clay, marine geotechnical engineering