Implementation of Hypoplasticity for Fast Lagrangian Simulations

The hypoplastic constitutive
equations by Wu with and without structure tensor and by von
Wolffersdorff were implemented in the finite element with explicit
integration program FLAC. The influence of material nonlinearity,
mass density and damping factor on numerical solutions with the
explicit method were studied and reported. The implementation of
hypoplasticity by Wu in FLAC was selected to simulate some
laboratory tests i.e. biaxial test and simple shear test. The
implementation was also used to simulate some typical geotechnical
problems i.e. a spread footing on cohesionless soil, a trapdoor
problem and an unlined circular tunnel. The results obtained with
hypoplasticity agreed well with analytical solutions and
experimental results. The hypoplastic constitutive equations and
an elasto-plastic one with Mohr-Coulomb failure criterion were
used to simulate normally consolidated Bangkok Clay. The
hypoplasticity by Wu was selected for modelling of shield
tunnelling in Bangkok Clay because the model gives good
predictions of the undrained behavior. The earth pressure
coefficient at rest K0 used in the shield tunnelling
simulations with FLAC is higher than the K0 obtained from the
Jaky's formula. The shield tunnelling was modelled by using actual
dimensions from the construction records to generate the mesh. The
surface settlements from the simulations are close to the
observations. The empirical method by Peck underpredicts the
surface settlements from observations.