Development of an adaptive meshing upper bound limit analysis method for large deformation axisymmetric geotechnical...

Area of Science:

• Geotechnical Engineering
• Computational Mechanics
• Soil Mechanics

Background:

• Traditional limit analysis methods have limitations in modeling complex soil behaviors and geometries.
• The original sequential limit analysis (SLA) method required extensions for broader applicability.

Purpose of the Study:

• To develop an enhanced sequential limit analysis (SLA) method in OPTUM.
• To extend SLA capabilities to include axis-symmetric problems and improve modeling of soil collapse under gravity.
• To validate the enhanced SLA method and explore its application in offshore engineering.

Main Methods:

• Extended the original SLA's plane-strain analysis to include axis-symmetric problems.
• Implemented refinements for nodal velocities during soil collapse, particularly with stiff soil berms.
• Validated the method against various penetration problems and conducted a parametric study on ball penetration.

Main Results:

• SLA simulations can be performed with displacement increments of approximately 1% of the object's characteristic size.
• Penetration resistance decreased by up to 34.5% in cases with strain softening compared to non-softening scenarios.
• An equivalent plastic strain factor was adopted to improve the accuracy of soil strength measurements.

Conclusions:

• The enhanced SLA method effectively models large deformation soil-structure interaction problems.
• It is a powerful tool for analyzing offshore engineering applications involving piles, spudcans, and penetrometers.
• The refined method enables proper modeling of extreme conditions and complex geometries in geotechnical analysis.