Experimental studies show that initial fabric and its evolution under different stress paths greatly influences soil behaviour. Even though different sample preparation methods create different inherent anisotropies and cause different material responses, the same initial fabric structure under different stress paths also results in different material behaviours. In this paper, a simple state-dependent, bounding surface-based elastoplastic constitutive model, which can simulate the anisotropic nature of sands including the effect of principal stress rotation, is described. The model is developed based on a semi-micromechanical concept within the multilaminate framework and, to include the inherent anisotropy of sand, a deviatoric fabric tensor describing the initial microstructure is introduced. In addition, a fabric evolution rule compatible with anisotropic critical state theory is employed to describe the evolving fabric structure and induced anisotropy towards the critical state. In contrast to the classical strain-driven formulation for fabric evolution, a micro-level evolution rule is proposed. This paper presents concise theoretical aspects of the multilaminate framework and the anisotropic elastoplastic constitutive formulation. The model's capability under drained and undrained monotonic loading conditions at different stress states, relative densities and principal stress orientations is demonstrated by simulating experimental data for Toyoura sand.

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This paper describes an MPM formulation using linear quadrilateral elements suitable for soil-structure-interaction problems. The volumetric locking and stress-oscillations are mitigated using a reduced integration technique and the Gauss integration scheme, respectively. The formulation can be used with both structured and unstructured computational meshes. In addition, an improved calculation scheme is proposed to obtain accurate contact reaction forces, especially for contacts between non-porous structures and soils with high liquid pressures. The formulation is validated by simulating a wide range of applications such as a water dam break, 1D large-strain consolidation, and the bearing capacity of a strip footing. Finally, the installation of a cone penetrometer in a centrifuge is successfully simulated in soft soils and compared with the experimental data for the entire range of drainage conditions.

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Cone penetration tests (CPTs) are widely used in geotechnical engineering for soil characterization and parameter determination. Throughout the years, experimental data have been used to determine correlations between CPT data and soil properties, such as stiffness or strength. Recent progress in advance numerical methods allows the simulation of the full CPT penetration by overcoming the limitations related to extreme deformations. The use of these numerical techniques provides new prospective to the soil characterization and determination of soil parameters, especially for the settings where limited (or no) experimental data is available and existing correlations are not accurate, or absent. This paper presents a numerical framework based on the Material Point Method (MPM) to simulate CPT in dry sand. First, it is proven that the calculation scheme is stable and accurate. Then, the model results are validated against chamber test data in terms of both cone resistance and displacement field during the penetration. Finally, some considerations about the formulation of the constitutive models of soils are presented, specifically oriented for CPT applications.

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Both the Material Point Method (MPM) and meshfree schemes based on optimal transport theory have been developed for efficient and robust integration of the weak form equations originating from computational mechanics. Although the methods are derived in a different fashion, their algorithms share many similarities. In this paper, we outline the close resemblance of MPM and Optimal Transportation Meshfree (OTM) schemes. Aside from a theoretical analysis, the methods are compared numerically using a one-dimensionalbenchmark.@en

Within the standard material point method (MPM), the spatial errors are partially caused by the direct mapping of material-point data to the background grid. In order to reduce these errors, we introduced a novel technique that combines the least squares method with the Taylor basis functions, called the Taylor least squares (TLS), to reconstruct functions from scattered data while preserving their integrals. The TLS technique locally approximates quantities of interest such as stress and density, and when used with a suitable quadrature rule, it conserves the total mass and linear momentum after transferring the material-point information to the grid. The integration of the technique into MPM, dual domain MPM, and B-spline MPM significantly improves the results of these methods. For the considered examples, the TLS function reconstruction technique resembles the approximation properties of highly accurate spline reconstruction while preserving the physical properties of the standard algorithm.

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Within the standard Material Point Method (MPM), the spatial errors are partially caused by the direct mapping of material-point data to the background grid. In order to reduce these errors, we introduced a novel technique that combines the Least Squares method with the Taylor basis functions, called Taylor Least Squares (TLS), to reconstruct functions from scattered data. The TLS technique locally approximates quantities of interest, such as stress and density, and when used with a suitable quadrature rule, conserves the total mass and linear momentum after transferring the material-point information to the grid. For one-dimensional examples, applying the TLS approximation significantly improves the results of MPM, Dual Domain Material Point Method (DDMPM), and B-spline MPM (BSMPM). Due to its outstanding conservation properties, the TLS technique outperforms the nonconservative reconstruction techniques, such as spline reconstruction. For example, in contrast to the solution generated using the global cubic-spline interpolation, the TLS solution satisfies the boundary conditions of a two-phase benchmark. Therefore, the TLS reconstruction increases the accuracy of the material point methods, while preserving the fundamental physical properties of the standard algorithm. @en

Static liquefaction is one of the principal triggering mechanisms of failure in fully saturated loose sand slopes both in offshore and onshore regions. Static liquefaction induced landslides are known for their significant softening and a fluid-like behavior at the onset of failure. However, the literature lacks experimentally verified advanced numerical approaches which are capable of simulating static liquefaction. In this study, an advanced constitutive model based on the multilaminate framework is used in a finite element code. Multilaminate model accounts for significant features such as rotation of principal stresses, anisotropy in the material, strain softening due to static liquefaction and stress and strain dependency of the stiffness which enable us to achieve a more realistic soil behavior. The analysis results are verified by a set of large scale experiments of static liquefaction failures in submerged slopes under monotonic loading. Presented numerical approach can be used as a tool for further investigations of static liquefaction induced flow slides. This is useful for design and optimization of static liquefaction mitigation techniques.@en