New paper: Separating fluid and solid contact constraints for hydro-mechanically coupled finite elements discretising fluid displacement

Left: Deformed configuration of the solid phase during pile driving and field of effective horizontal stress.
Right: Deformed configuration of the fluid phase
During uplift of the pile, only the fluid phase follows the pile, while the solid phase separates from the pile tip

How to model the interface between a structure and a saturated porous medium?

In our latest paper published in ๐˜Š๐˜ฐ๐˜ฎ๐˜ฑ๐˜ถ๐˜ต๐˜ฆ๐˜ณ ๐˜”๐˜ฆ๐˜ต๐˜ฉ๐˜ฐ๐˜ฅ๐˜ด ๐˜ช๐˜ฏ ๐˜ˆ๐˜ฑ๐˜ฑ๐˜ญ๐˜ช๐˜ฆ๐˜ฅ ๐˜”๐˜ฆ๐˜ค๐˜ฉ๐˜ข๐˜ฏ๐˜ช๐˜ค๐˜ด ๐˜ข๐˜ฏ๐˜ฅ ๐˜Œ๐˜ฏ๐˜จ๐˜ช๐˜ฏ๐˜ฆ๐˜ฆ๐˜ณ๐˜ช๐˜ฏ๐˜จ (CMAME) we present a mortar contact discretization scheme enforcing contact constraints separately for the pore fluid and the solid.

Back-calculation of vibratory pile driving tests shows that the proposed scheme increases both numerical stability as well as predictive capabilities of the simulation compared to contact methods not distinguishing between contact constraints for the solid phase and the fluid phase.

Free access to the paper until November 12th:

New paper: A theory of porous media for unsaturated soils with immobile air

In most works, unsaturated soil is considered a three-phase medium composed of air, water, and solid, neglecting effects caused by the presence of residual water and/or entrapped (immobile) air.

We present a set of governing equations for unsaturated soils with residual water and entrapped air considering a mass transfer mechanism between the free air and the entrapped air. The performance of the model is examined in simulations of water retention curves, a rapid drawdown experiment as well as in the dynamic analysis of a centrifuge test on a dam subjected to earthquake loading.

Free access to the paper until April 12th:,63b-0MRi

New paper: Deep vibratory compaction

Determining the achieved densification by deep vibratory compaction is a challenging task, both practically and numerically.

In the framework of a DFG Project (German Research Council) and in cooperation with Keller Grundbau we have developed an efficient numerical scheme to estimate the effects of deep vibratory compaction using numgeo. A paper describing the approach has now been published in Soil Dynamics and Earthquake Engineering.

Free access to the paper until March 7th:

New paper: Factor of Safety for slopes subjected to earthquake loading

How to determine a Factor of Safety of water-saturated slopes under earthquake loading accounting for material-induced failure and the role of pore-fluids? Not an everyday question, but all the more challenging for it.

Together with Christoph Schmรผdderich (corresponding author), Felipe Prada and Torsten Wichtmann we present an extended strain-dependent slope stability concept by Nitzsche and Herle (2020) which allows advanced constitutive models to be included in the analysis. Tolerable computation times are achieved by using machine learning algorithms.

Free access to the paper until November 30th:,63b~yZ2I

New numgeo release

We have now released a new numgeo version, with plenty of new features, bugfixes and new examples.

In particular, we have added

  • an example for a 3D monopile simulation using the HCA model and
  • examples for infiltration problems using the 3-phase elements in numgeo.
  • a simulation of a 3D pile with comparison of the results to a commercial code

Some specific new features:

  • Compliant base boundary conditions
  • Including external files in input file
  • AVISA-2022 (thanks to Merita Tafili!)
  • Karlsruhe hydraulic model (soil water retention curve accounting for void ratio dependence and scanning curves)
  • Modified Cam-Clay (โ€Terzaghiโ€- and โ€Butterfieldโ€-version)
  • Matsuoka-Nakai model (thanks to Christoph Schmรผdderich!)
  • Support of (arbitrary) user-defined external solvers
  • Variable bishop effective stress parameter

The keyword reference manual contains a list of bugs we have resolved since the initial release…