Liquefaction phenomena are encountered in many engineering applications, especially, in geomechanics and earthquake engineering. Drawing our attention to fluid‐saturated granular materials with heterogeneous microstructures, the modelling is carried out within a continuum‐mechanical framework by exploiting the macroscopic Theory of Porous Media (TPM) together with thermodynamically consistent constitutive equations. In this regard, the solid skeleton of the water‐saturated soil is described as an elasto‐plastic material with isotropic hardening and a stress‐dependent failure surface. The underlying equations are discretised and implemented into the coupled porous‐media finite‐element solver PANDAS and linked to the commercial finite‐element package Abaqus via a general interface. This coupling allows the definition of complex intial‐boundary‐value problems through Abaqus, thereby using the sophisticated material models of PANDAS. To reveal the capabilities of this approach, two types of simulations have been carried out. At first, in order to get a detailed understanding of the porous‐media soil model under transient loading conditions, a cyclic torsion benchmark is computed. In a second step, specific liquefaction phenomena are addressed, where the underlying initial‐boundary‐value problems are inspired by practically relevant scenarios.

The VARTM procedure is a manufacturing step in the production line when building parts made of fibre-reinforced plastics (FRP), such as glass-or carbon fibre-reinforced plastics acronymed GFRP or CFRP, respectively. In the VARTM process, an initially dry (gas-saturated) fibre-fabric is gradually impregnated by resin, where the flow process is, besides the driving injection pressure, governed by the mutual interactions between the fabric, the resin and the ambient air. To predict the mechanical properties of the manufactured structure, simulations are vital.Within the present contribution, the simulation model proceeds from the macroscopic Theory of Porous Media (TPM), which intrinsically accounts for the interplay between the individual components, in particular, the fibre-network, the ambient air and the resin, where the latter two simultaneously percolate through inter-fibrous pore space. The underlying holistic modelling approach allows, on the one hand, for a continuous transition from the fully gas-saturated towards the fully resinsaturated state and, on the other hand, the consideration of the so-called spring-back effect. The presented simulation example investigates the model behaviour within a practically relevant application scenario. Infiltration modelIn the VARTM procedure, the initially dry fibre-fabric is placed in a single-pieced rigid mould which is, at first, airtight sealed and, subsequently, exposed to an underpressure, thereby compacting the textile by the ambient pressure. Next, an open (exposed to the ambient pressure) resin reservoir is attached to the inlet. The establishing saturation and pressure gradients between the inlet and the outlet initiate a resin flow, in particular, a convection-diffusion driven multiphasic flow process.The governing mathematical model is based on [1], where the TPM is exploited as the underlying modelling framework. The underlying description results in a fully coupled triphasic model composed of the dry fabric, the resin and the ambient air, which are, in what follows, denoted as the solid skeleton, the pore liquid and the pore gas, respectively. Note that the former two are treated to be materially incompressible, whereas the latter is materially compressible. With respect to the slow infiltration process, the model is confined to quasi-static loading conditions. Note that, in contrast to [1], the model has been slightly altered to better match the process variables. In particular, the partially saturated domain is governed by the prominent Brooks & Corey law, the solid is treated as a soft but purely elastic material and the primary variables are the solid displacement u S , the pore-liquid saturation s L and the effective pore-liquid pressure p LR . The description within the partially saturated domain follows the experimental observations of [2], who identified, with respect to the arising flow conditions, the pore gas as the wetting and the pore liquid as the non-wetting fluid on the one hand and determined the underlying material parameters associated...

The foundation of buildings proceed from a detailed analysis of the interaction between the building and its environment in order to reduce the costs and ensure safety of the construction. A detailed and reliable analysis of the building-foundation interaction requires suitable material definitions, an accurate description of the underground, and a model describing the geometry. Following this, a fluid-saturated soil model, based on the the Theory of Porous Media, will be implemented into the finite-element research-code PANDAS, which will be connected to commercial FE package Abaqus. In this regard, one combines the powerful graphical user interface (GUI) for pre-and post-processing and the algorithms of Abaqus with the convenient scripting environment for material definitions of PANDAS. Moreover, the linkage allows for a straight-forward transfer of PANDAS material models into a well-known and widely used commercial FE package.

Phenomena related to porous media dynamics, such as wave propagation and liquefaction, are encountered in many engineering applications, especially, in geomechanics and earthquake engineering. Drawing our attention to fluid‐saturated granular materials with heterogeneous microstructures, the modelling is carried out within a continuum‐mechanical framework by exploiting the well‐established macroscopic Theory of Porous Media (TPM) together with thermodynamically consistent constitutive equations. In this regard, the solid skeleton of the soil is described as an elasto‐plastic material. The underlying equations are discretised and implemented into the coupled porous‐media finite‐element solver PANDAS and linked to the commercial finite‐element package Abaqus through a general interface. This coupling allows the definition of complex intial‐boundary‐value problems through Abaqus, thereby using the state‐of‐the‐art material models of PANDAS. In order to get a detailed understanding of the behaviour of the underlying soil model under dynamic loading conditions, a cyclic torsion test is numerically investigated. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Numerical simulations have proven to be a powerful tool in several engineering disciplines, such as mechanical, civil and biomechanical engineering, and are thus widely used. However, the reliability of the simulations strongly relies on the governing material model. These models are usually developed in academic or industrial research projects and are implemented into dedicated software packages to proof their concepts. A transfer of these models from the research into a productionrelated environment is often time consuming and prone to failures, and therefore a costly task.The present work introduces a general interface between the research code PANDAS, which is a dedicated multi-field finite-element solver based on a monolithic solution strategy, and the commercial finite-element package Abaqus. The coupling is based on the user-defined element subroutine (UEL) of Abaqus. This procedure, on the one hand, allows for a straight-forward embedding of the PANDAS material models into Abaqus. On the other hand, it provides, in comparison to the native UEL subroutine of Abaqus, a user-friendly programming environment for user-defined material models with an extended number of degrees of freedom. Furthermore, the coupling also supports the parallel-analysis capabilities for large-scale problems on high-performance computing clusters.The Abaqus-PANDAS linkage can be applied to various coupled multi-field problems. However, the present contribution addresses, in particular, volume-coupled multi-field problems as they arise when proceeding from the Theory of Porous Media (TPM) as a modelling framework. For instance, it can be used to model partially or fully saturated soils, or chemically or electro-chemically driven swelling phenomena as they appear, for example, within hydrogels. Additionally, discontinuities, such as cracks, can be described for instance via phase-field models or by the extended finite-element method (XFEM).