This paper presents an investigation into the suitability of the SANISAND-MS model for the three-dimensional finite-element (3D FE) simulation of cyclic monopile behaviour in sandy soils. In addition to previous work on the subject, the primary focus of this study is to further assess the model's capability to reproduce the accumulation of permanent deflection/tilt under cyclic lateral load histories. To this end, experimental data from the PISA field campaign are employed, particularly those emerged from the medium-scale cyclic tests conducted at the Dunkirk site in France. The methodology adopted herein involves calibrating the SANISAND-MS model's parameters to align with 3D FE simulation of a selected monotonic pile test reported by the PISA team using a bounding surface plasticity model partly similar to SANISAND-MS. Subsequently, the soil parameters governing SANISAND-MS’ ratcheting response are calibrated using only minimal information from published PISA field data. While representing the first attempt to simulate the reference data set using a fully ‘implicit’ 3D FE approach, this paper offers novel insights into calibrating and using advanced cyclic models for monopile analysis and design – particularly, with regard to the quantitative influence of pile installation effects and sand's microstructural evolution under drained cyclic loading.@en

Understanding and properly simulating discontinuity mechanical behaviour is crucial in all rock engineering projects. Several constitutive relationships have been proposed and implemented in numerical codes. This paper discusses the results of a numerical study that exam-ines the influence of adopting different rock discontinuity constitutive models for simulating the behavior of a fractured rock mass. Two constitutive approaches are employed: an enhanced Cou-lomb-based criterion with strain softening and a modified version of the Barton-Bandis model to overcome potential implementation issues. These models have been implemented in PLAXIS and their performance is inspected through numerical analyses of an underground cavity for a specific discontinuity network geometry. The results provide insights into the implications and suitability of adopting different discontinuity constitutive models for assessing the stability of engineering works in fractured rock masses.@en

This paper discusses some numerical analyses performed with a generalized three-dimensional Hoek & Brown (HB) model which strength criterion has been considered to simulate the mechanical behavior of rocks in brittle conditions. For this purpose, this constitutive framework has been enhanced with hyperbolic softening and non-linear dilation, thus enabling to investigate failure modes in the form of dilating shear bands. To restore the objectivity of the numerical solution during the development of localized strain, a viscous regularization technique has been employed to simulate localization phenomena in two different initial boundary value problems, both computed by using the finite element software PLAXIS 2D: (i) a biaxial test, and (ii) a tunnel excavation problem simulated through a deconfinement process. While the former has been considered to test the effect of the viscous parameter in governing the structural behavior of the rock sample, the latter has been selected to model the shear bands propagation during the process of a tunnel excavation in which the rocks mass has been characterized by different mechanical properties. The computed solutions have been compared with existing formulations based on the framework of HB strength criteria, thus enabling to further validate the implementation of the proposed constitutive equations.@en

Energy foundation technology is expected to make a significant contribution to the use of renewable energy. In this context, this paper presents the use of Finite Element simulation using PLAXIS software for modelling different benchmark applications in Geothermal Foundations. An implicit fully-coupled numerical scheme with global adaptive time stepping are implemented to ensure computational efficiency and stability. Firstly, a transient simulation of thermal response tests [1], often used to estimate the thermal conductivity of ground and thermal resistance of pile, is presented. In the second part, a Thermo-Hydro-Mechanical analysis is performed to simulate the behavior of a single heat pile subject to a thermal load cycle [2]. Several ingredients (constitutive behavior, interface finite elements etc.) are employed to simulate soil-structure interactions. The obtained solutions are validated against available simulation and experimental data to demonstrate the applicability of the simulator to energy foundation analysis and design.@en

When saturated soils are subjected to an earthquake, the excess pore pressuresincrease, and, in the case of sands, this may cause liquefaction. To simulate the behaviour of saturated sands under cyclic loading, the PM4Sand constitutive model (version 3.1) formulated by Boulanger & Ziotopoulou (2017), is used. The PM4Sand model represents an improvement of the elasto-plastic, stress ratio controlled, bounding surface plasticity model formulated by Dafalias & Manzari (2004). The model can realistically reproduce the pore pressure build-up, accumulation of strain as well as triggering of liquefaction. In this paper, the effect of different relative densities on liquefaction resistance is evaluated by comparing the results of a site response analysis performed on a soil column characterized by a saturated sand layer and subjected to given earthquake signals. The analyses are performed using the finite element code PLAXIS.@en

Hoek & Brown (HB) failure criteria have been employed over the past decades in common engineering applications due to their extended capability to capture the non-linear yielding of different types of rocks. Often implemented within a perfect plastic framework, this constitutive approach is here enhanced by introducing a softening rule to simulate the post-peak behaviour of rocks in the brittle regime. For this purpose, the degradation of the material properties has been expressed as a function of an internal variable (i.e., the cumulated value of deviatoric plastic strains) which allows one to simulate the rock failure resulting from dilating shearing. Furthermore, to accurately describe the non-linear dilatancy after the peak, the same hyperbolic trend has been applied also to the material properties governing the expression of the plastic potential. The performance of these constitutive equations has been inspected through parametric analyses to emphasize the role of the softening parameters at material point level, as well as to study the strain localization potential of the Hoek & Brown model with Softening (HBS). As a further validation, the shear band angles predicted with the theory have been compared by performing the same tests with finite element code PLAXIS 2D, thus confirming the model capability to simulate failure mechanisms within a strain localization regime.@en

To simulate the behaviour of saturated sands under cyclic loading, the PM4Sand constitutive model (version 3.1) formulated by Boulanger & Ziotopoulou [1], is used. The model can realistically reproduce the pore pressure build-up, accumulation of strain as well as triggering of liquefaction. The effect of dif-ferent relative densities on liquefaction resistance is evaluated by comparing the results of a site response analysis performed on a soil column character-ized by a saturated sand layer and subjected to given earthquake signals. The analyses are performed using the finite element code PLAXIS.@en