THESIS
2014
xxi, 147 pages : illustrations (some color) ; 30 cm
Abstract
Numerical simulations of hydro-mechanical coupling systems are of great importance in
understanding the soil-water coupling problems generally encountered in geotechnical
engineering. In this thesis, an innovative numerical procedure is developed to solve the
hydro-mechanical coupling systems using Reproducing Kernel Particle Method (RKPM).
Compared with the conventional Finite Element Method, RKPM, one type of meshfree
methods, is free from the burden of mesh construction and can avoid deteriorated
accuracy when large deformation occurs. To gain
flexibility in numerical implementation,
a sequential solution strategy is applied to solve the primary unknowns iteratively
between the solid solver and
fluid solver. Stability of the sequential scheme is ensured
through the intro...[
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Numerical simulations of hydro-mechanical coupling systems are of great importance in
understanding the soil-water coupling problems generally encountered in geotechnical
engineering. In this thesis, an innovative numerical procedure is developed to solve the
hydro-mechanical coupling systems using Reproducing Kernel Particle Method (RKPM).
Compared with the conventional Finite Element Method, RKPM, one type of meshfree
methods, is free from the burden of mesh construction and can avoid deteriorated
accuracy when large deformation occurs. To gain
flexibility in numerical implementation,
a sequential solution strategy is applied to solve the primary unknowns iteratively
between the solid solver and
fluid solver. Stability of the sequential scheme is ensured
through the introduction of a relaxation term and is proved through stability analysis.
Like conventional Finite Element Method without special treatment, spurious oscillations
in pore
fluid pressure distribution are frequently encountered under incompressible
and impermeable conditions. An extra stabilization technique is therefore adopted to
suppress the unphysical oscillations. The numerical procedure for solving the hydro-mechanical
coupling systems is verified through simulations of one- and two-dimensional
consolidation problems within elastic medium and comparisons with the analytical
solutions. The effects of related influencing factors such as the support size and relaxation
parameter on the convergence behavior are also investigated.
To better simulate the mechanical behaviors of dense and loose sands under complex loading conditions, a modified bounding surface hypoplasticity model is developed in
this thesis. Modifications of the dilatancy relationship are proposed to make the model
capable of simulating the cyclic mobility of dense sands and
flow liquefaction of loose
sands. The capability of the proposed soil model is demonstrated through comparisons
between numerical simulations and laboratory tests of sands with different densities under
undrained simple shear loading of various cyclic shear stress ratios.
Finally, both Mohr-Coulomb model and bounding surface hypoplasticity model
are implemented in the numerical procedure to simulate a variety of boundary value
problems, including plane strain biaxial compression test, strip footing problem and
vertical slope problem. Simulations of strain localization under both drained and
undrained conditions are highlighted. The regulatory effects of node refinement and
the dilation parameter in the simulation of strain localization are also demonstrated. It
is also shown that the modified bounding surface hypoplasticity model can adequately
capture the different dilatancy behaviors of dense and loose sands during the shear band
formation process.
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