Mr. Blanksma develops numerical modeling software for engineering applications. His area of expertise includes finite volume/difference and discrete element numerical methods. His experience includes GUI development for building meshes in continuum codes. Additionally, he has helped in the development of the 2D continuum code FLAC2D. The projects included implementing the Dynamics, and most recently, the Interface functionality in the code.
FLAC3D TMis a numerical modeling code for advanced geotechnical analysis of soil, rock, and structural support in three dimensions. FLAC3D is used in analysis, testing, and design by geotechnical, civil, and mining engineers.
This FLAC3D V7.0 training course accommodates new and experienced users. It will be based on examples that attendees will develop and run by themselves to better grasp the mechanics of using FLAC3D V7.0, the key underlying calculation principles and the spectrum of available features. Attendees are encouraged to bring one of their specific cases that may be discussed.
The upcoming 70th annual Highway Geology Symposium will be held in Portland, Oregon, October 21st through October 24th, 2019.
Dr. Detournay has experience in the development of numerical models for application to coupled fluid-thermo-mechanical problems. She is a principal developer for the groundwater-flow and thermal logic in FLAC3D, and has been involved in the development of several of the constitutive models available with Itasca continuum codes.
Itasca is pleased to introduce the P2P-Sand (Practical Two-Surface Plasticity model for Sands) model, a new practice-friendly 3D liquefaction constitutive model for FLAC3D that is based on the DM04 (Sanisand) model (Dafalias & Manzari, 2004). By revising some formulas without destroying the conciseness of the original DM04 (Sanisand) model, the improved comparative results between model simulations and lab/field observations are obtained under various initial conditions and loading conditions. In addition, the new liquefaction model provides an easier, more practical calibration procedure in terms of in situ data (instead of experimental data), greatly reducing the labor of calibration.
Itasca's P2P-Sand constitutive model:
Learn more about this powerful and easy-to-use solution by downloading Itasca engineer Dr. Zhao Cheng’s GEESD V conference presentation:
A Practical 3D Bounding Surface Plastic Sand Model for Geotechnical Earthquake Engineering Application (PDF, 4 MB)
NorSand (Jefferies 1993, Jefferies and Been 2015)
is a critical state model applicable to soils in which
particle-to-particle interactions are controlled by contact forces and
slips rather than bonds, intrinsically incorporating the state parameter
so that it captures the behavior of granular soils over a wide range of
confining stresses and densities. NorSand requires relatively few soil
properties which are familiar and can be estimated from routine
laboratory or in-situ tests (e.g., CPT data).
NorSand explicitly captures the full range of soil behavior, from
static liquefaction of very loose soils through to dilation of very
dense soils. It is suitable for simulating the typical brittle collapse
(i.e., flow liquefaction) of a soil structure being over-surcharged,
slope-steepened, or sudden rising of pore-pressure. The model is
frequently applied to tailings dam analysis.
FLAC3D's implementation also considers the effect of Lode’s
angle so that the shear strengths with different second principal
stresses can be distinguished. The recent developed feature of principle
stress rotation is also incorporated so that the cyclic mobility can be
simulated as well as static liquefaction. The results were
cross-verified with a VBA-coded spreadsheet for simulations of various
densities, drainage conditions, and test types (including triaxial
compression and simple shear).
The following figure demonstrates just how well NorSand in FLAC3D 7
(red, solid curves) compares to measured direct simple shear (DSS)
testing (blue, dashed curves) considering the effects of principal
stress rotation (PSR).
Soft soils generally refer to normally consolidated or slightly
over-consolidated clays, silty-clays, clayey silts, and peats.
Significant compression, is one of the main engineering characteristics
of soft soils, where:
The soft-soil (SS) model has the following features: (a)
pressure-dependent moduli; (b) unloading-reloading distinct from the
virgin loading; (c) expansion of the volumetric yield ellipse-shaped
cap; and (d) conventional Mohr-Coulomb shear failure and tension failure
The Soft-Soil (SS) model cannot simulate time-dependent behavior, such as the creep that develops during the secondary compression. The creep behavior of soft soil can be significant for some geotechnical engineering problems, e.g., embankment construction. The Soft-Soil-Creep (SSC) model (Vermeer and Neher, 1999) takes time-dependence into account so that the volumetric cap expands to a new position within a specific time (called reference time in the model) instead of instantaneously as in the SS model. Furthermore, the cap will never stop expanding — although with a continuously decreasing expansion rate. The expansion rate will be determined by the value of the current OCR. When OCR is high, creep deformation is neglectable. The SSC model has the following features: (a) secondary time-dependent compression; (b) pressure-dependent moduli; (c) unloading-reloading distinct from the virgin loading; (d) memory of the equivalent pre-consolidation pressure; and (e) degeneration to a conventional Mohr-Coulomb failure criterion when the creep time step is zero.
The option of small-strain stiffness is added to the Plastic-Hardening model to take strain-dependency of the modulus into account. Whereas the PH model assumes an elastic material behavior during unloading and reloading for very small strains, with the small-strain formulation soil stiffness behaves nonlinearly with increasing strains. Inclusion of this option is believed to improve the accuracy of the simulated deformation. The PHSS formulation is enabled by the model property flag zone property flag-smallstrain on.
zone property flag-smallstrain on