Development of an adaptive meshing upper bound limit analysis method for large deformation axisymmetric geotechnical problems
Xingchao Chen, Z. Y. Wang, Deqiong Kong, Xulong Lou, Bin Zhu
Abstract
This research introduces the development of a sequential limit analysis (SLA) method in OPTUM. The plane-strain analysis capability of the original SLA has been extended to encompass both plane-strain and axis-symmetric problems, and the usability has been expanded to a broader spectrum of users. Moreover, refinements in addressing nodal velocities during soil collapse under gravity, specifically in scenarios featuring a stiff soil berm leading to slope instability, have been implemented, to enable proper modelling of more extreme conditions and complex model geometries. A detailed validation has been made against various penetration problems. It is revealed that SLA simulations can be executed with displacement increments at the order of 1% of the characteristic size of the object. In addition, a succinct parametric study on ball penetration is presented. Penetration resistance with strain softening is reduced by up to 34.5% compared to the non-softening case. An equivalent plastic strain factor was adopted to enhance the accuracy of measuring soil strength through ball penetrometer tests. The enhanced SLA method could also serve as a powerful tool for analysing large deformation soil-structure interaction problems for piles, spudcans, and cone / ball penetrometers in offshore engineering.