Allgemein

Cyclic loading of soils often involves complex stress and strain paths. In a new paper in the International Journal for Numerical and Analytical Methods in Geomechanics, we investigate the HCA model for complex cyclic loading with multidimensional loading paths and extend it for frequently changing loading amplitudes and directions in numgeo. This extension is validated by simulation of model tests on piles for offshore wind turbines subjected to multidimensional lateral loading with thousands of cycles.

Check out the full open-access article here.

numgeo now features mixed implicit-explicit (IMEX) schemes for efficient handling of challenging soil dynamics problems. The scheme is published in Computers and Geotechnics and the open access article is available here.

The IMEX scheme enhances efficiency by allowing larger time increments for stiff parts of the system (e.g. a pile), while maintaining accuracy for the less stiff domains (soil). This results in reduced computational time, especially in cases where purely explicit methods would require significantly smaller time steps to remain stable.

We are excited to share our latest research, “Numerical Modelling of Expansive Geomaterials: Finite Element Formulation and Constitutive Models,” published in Computers and Geotechnics!

Together with Antonia Nitsch (RUB), Torsten Wichtmann (RUB), and Carlos Grandas (BTU Cottbus), we delve into the challenging behavior of expansive soils, which can swell when in contact with water, leading to significant changes in volume or the development of swelling pressure. We propose a novel finite element framework based on the Theory of Porous Media (TPM), introducing a hydro-mechanically coupled hypoplastic constitutive model. All implemented in the finite element code numgeo.

Some key highlights:

• A three-dimensional hydro-mechanically coupled hypoplastic constitutive model for expansive soils, predicting both swelling strain or swelling stress depending on boundary conditions.
• A mass transfer mechanism handling the transition from free water to swelling water, directly affecting hydraulic conductivity.
• Demonstrated accuracy through laboratory test simulations.

Check out the full article here

An animation of an unconfined swelling test on an Opalinus clay sample between two filter plates with water supply from both top and bottom is shown below.

We are pleased to announce the publication of our latest paper in Géotechnique, where we present a critical investigation of three constitutive models for clay. Our study involves an in-depth analysis of a sophisticated laboratory testing program and back-calculation of centrifuge tests on monopiles in clay subjected to monotonic and cyclic lateral loading using numgeo and Abaqus.

The study examines constitutive models of varying complexity:

• Modified Cam Clay model (MCC): The basic model used as a benchmark.
• Hypoplastic model with intergranular strain: Also known as the clay hypoplasticity model, which accounts for intergranular strain effects.
• Anisotropic Visco-Intergranular Strain Anisotropy (AVISA) model: A recently proposed model that incorporates anisotropic visco-intergranular strain behavior.

Dive into the full article for detailed insights and implications for future research and practical applications.

We are thrilled to announce that numgeo is now integrated into the GiD Pre- and Postprocessor. With this integration, you can leverage GiD’s powerful geometry and meshing features for preprocessing tasks. An intuitive data tree simplifies the finite element model creation process by displaying only the relevant settings, thereby streamlining your workflow.

We presented these developments at the 12th GiD Convention on Advances and Applications of GiD. For a recording of the presentation and future updated visit the dedicated Graphical User Interface page.