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In recent years, data-driven approaches have gained considerable momentum in the scientific and engineering communities, owing to their capacity to extract complex patterns from high-dimensional data. Despite their potential, these approaches often require extensive high-quality datasets, may exhibit limited extrapolation capability beyond the training domain, and lack a rigorous foundation grounded in physical and thermodynamic principles. To overcome these limitations, physics-informed neural networks have been introduced, embedding governing equations directly into the learning process. Building upon this paradigm, this study presents a novel thermodynamically consistent constitutive model for granular soils, developed within the framework of geotechnically- and physics-informed neural networks (GINN). The model integrates physical laws with data-driven learning via a composite loss function. These include: (i) strictly non-negative material dissipation rate to ensure thermodynamic admissibility, (ii) an admissible range for the predicted stress state, and (iii) bounds on the predicted void ratio. The material dissipation rate is calculated using the total work input and a free energy potential expressed in terms of stress invariants. The model is validated against monotonic drained triaxial test data for specimens prepared with diverse initial void ratios and stress states. The model accurately simulates both the shear strength and dilative response of granular soil samples. Its predictive performance is further benchmarked against two widely adopted constitutive models from the literature, demonstrating comparable accuracy while maintaining consistency with thermodynamic laws.

This study examines the behavior of anisotropically consolidated granular assemblies under undrained cyclic true triaxial loading paths. To achieve this, the Discrete Element Method (DEM) is conjugated with the Coupled Fluid Method (CFM) to account for fluid-solid interaction in undrained conditions. The examined loading paths include two phases: anisotropic consolidation and undrained cyclic true triaxial loading. During consolidation, samples are sheared at various Lode angles to reach a spectrum of initial static shear stress levels. In the second stage, undrained cyclic loading is applied with constant shear stress amplitudes at various Lode angle values. The results indicated that the monotonic and cyclic Lode angle, initial static shear stress, and amplitude of deviatoric stress have pronounced effects on the secant shear modulus degradation and the rate of excess pore water pressure generation of granular assemblies. In tandem with macro-scale observations, the evolution of the microstructure within assemblies is analyzed using the coordination number, redundancy index, inter-particle contact fabric tensor, and particle orientation fabric tensor. The micro-scale findings confirm that the anisotropy induced by changes in the loading direction significantly impacts the shear strength of the assemblies. Additionally, the fabric of assemblies aligns along the preferential direction corresponding to the major principal stress, influencing the dilative response.

The paper presents an experimental study on the effect of plastic fines content on the undrained behavior and liquefaction susceptibility of sand–fines mixtures under monotonic loading. The results of undrained monotonic triaxial compression tests conducted on mixtures of Hostun sand with varying amount (0–20%) and type (kaolin and calcigel bentonite) of plastic fines are presented. The specimens were prepared with different initial densities using the moist tamping method and consolidated at two different isotropic effective stresses. The results demonstrate that for both types of plastic fines, an increase in the fines content leads to a more contractive response and lower values of mobilized deviatoric stress. Despite similar relative density and fines content, the sand–kaolin mixtures showed a more contractive behavior than the sand–calcigel specimens. The steady-state lines (SSLs) in e–p´ space generally move downwards with increasing clay content. While the slopes of the SSLs for the clean Hostun sand and the mixtures with 10 and 20% kaolin are quite similar, the SSL lines for the specimens containing 10% or 20% calcigel run steeper or flatter, respectively. The inclination of the SSL in the q–p′ plane was found independent of clay type and content. The sand–kaolin mixtures were observed to be more susceptible to instability and flow liquefaction than the sand–calcigel mixtures.

A high-cycle accumulation (HCA) model predicting the accumulation of permanent strain or excess pore water pressure in clay under a large number of load cycles is presented. Data from an extensive laboratory testing program on kaolin under undrained cyclic loading has been analysed for that purpose. The influence of strain amplitude, void ratio, stress ratio, overconsolidation ratio and loading frequency on the accumulation rates is considered in the constitutive equations of the HCA model. The proposed model is validated first by the simulation of element tests. Subsequently, its application to offshore wind turbine foundations under long-term lateral cyclic loading is presented by the back-analysis of a centrifuge test on a monopile in soft clay. The results are in good accordance with the measurements in terms of pile displacement and bending moment versus number of applied cycles. It is concluded that the proposed model is feasible to describe the long-term behaviour of clay subjected to high-cyclic loading.

The hypoplastic model for sands proposed by Wolffersdorff (Mech Cohes Frict Mater 1: 251–271, 1996) combined with the intergranular strain anisotropy by Fuentes and Triantafyllidis (Int J Numer Anal Meth Geomech 39: 1235–1254, 2015) is herein extended to account for cyclic mobility effects to allow for the simulation of liquefaction phenomena. The extension is based on the introduction of an additional state variable that permits the detection of cyclic mobility paths. The simulation capabilities of the model is compared with undrained triaxial tests of Karlsruhe fine sand. At the end, a finite element simulation of an offshore monopile embedded in sand, exposed to environmental forces from the Caribbean Sea, is constructed and analyzed.

The paper presents an experimental study on the effect of plastic fines content on the undrained behavior and liquefaction susceptibility of sand-fines mixtures under cyclic loading. The results of undrained cyclic triaxial tests conducted on mixtures of Hostun sand with varying amounts (0–20%) and types (kaolin and calcigel bentonite) of plastic fines are presented. The specimens were prepared with different initial densities using the moist tamping method, consolidated at the same isotropic effective stress of 100 kPa and subjected to different deviatoric stress amplitudes. From the experimental observations, it was found that sand-clay mixtures with 10% or 20% clay content showed a lower cyclic liquefaction resistance than pure sand. Furthermore, the reduction in the cyclic stress ratio resulting in liquefaction after twenty cycles was found larger for sand-kaolin mixtures than for the sand-calcigel ones. Possible explanations are provided.

An experimental study regarding the thermo-mechanical behaviour of a Malaysian Kaolin is presented in this paper. Mercury intrusion porosimetry (MIP) tests have been performed on compacted samples with varying initial water contents. Samples compacted at dry side of optimum showed a bi-modal pore size distribution (PSD), while samples compacted at optimum or wet side of optimum showed a mono- modal PSD. The potential of the soil for thermal collapse was evaluated using the data of the MIP tests. It was concluded that soils with a bi-modal PSD (dry of optimum) have the potential for thermal collapse while soils with a mono-modal PSD (optimum/wet of optimum) usually show a dilative behaviour. This dilative behaviour was later confirmed using the data obtained from heating saturated, highly OC samples to a desired temperature. By performing temperature controlled oedometer tests in the range of T = 20°C to T = 90°C on saturated samples it was shown that the apparent preconsolidation pressure decreases with increasing temperature. Furthermore, the influence of temperature on the compressibility was evaluated suggesting that temperature has no influence on the compression index and the swelling index while the recompression index decreases with increasing temperature.

Fiber-reinforced soils are widely used in the field of geotechnics to enhance slope stability. Still, proper consideration of fiber inclusions for slope stability analyses remains challenging since advanced consti- tutive models for fiber-reinforced soils can usually not be used for slope stability analyses. The main reason for this is that popular methods to investigate slope stability, for instance limit equilibrium method, limit analy- sis or strength reduction finite-element analysis, are mostly restricted to the use of simple constitutive models. Thereby, shear strength and dilation response of reinforced soil assemblies cannot be properly captured. In this study, “strain-dependent slope stability” (SDSS) is used to evaluate the stability of fiber-reinforced soil slopes as it allows the use of sophisticated constitutive model for slope stability analyses. For this, a new hyperelastic- plastic model has been developed that incorporates a new state parameter influenced by fiber inclusion. For validation of the model, simulations in element scale are compared with experimental data of triaxial tests. Af- terwards, the model is implemented in ABAQUS as a user-defined material routine for slope stability analyses. To show the capability of the new approach, slope stability analyses are conducted for fiber-reinforced soils, considering variations of fiber content.

The properties of partially saturated soils are essential for geotechnical engineering since the majority of construction work takes place in the unsaturated zone between the ground surface and the groundwater table. The presence of air-water interfaces in partially saturated soils influences both the suction and stress state of the soil, and thus important soil properties like shear strength and stiffness. This research investigates the water retention and strength properties of a partially saturated sand-clay mixture exposed to different hydraulic paths. Pressure plate and desiccator tests were performed to investigate the interaction between suction and soil water content. In the analysis of the strength characteristics, the concept of suction stress was employed. Suction stress was determined from strain-controlled uniaxial compression tests on about 100 specimens, which were previously subjected to different drying and wetting paths. In this context, the impact of hydraulic hysteresis on suction stress is thoroughly examined. This article further evaluates mathematical equations for describing both the soil water characteristic curve (SWCC) and the suction stress characteristic curve (SSCC). Equation-specific benefits and problems are addressed, using statistical evaluation and error quantification.

Microbially Induced Calcite Precipitation (MICP) is an innovative soil improvement method that enhances the mechanical properties of different soil types through biological processes. Among various MICP pathways, urea hydrolysis mediated by ureolytic bacteria is the most widely used. Traditionally, exogenous ureolytic bacteria have been employed to accelerate calcite precipitation in soils, known as the bioaugmentation approach. However, this method is associated with some challenges, such as environmental impacts from introducing large volumes of non-native bacteria into natural soils, high material usage, and non-uniform spatial calcite precipitation. In contrast, recent studies suggest that these challenges can be reduced through the biostimulation approach, which is based on the enrichment of native ureolytic bacteria in soils. To determine the feasibility of replacing bioaugmentation with biostimulation for different soil types, a direct comparison between the treatment results from the two approaches is necessary. In this study, two soils with varying grain size distribution curves from the Rhenish lignite mining area in Germany were treated using both bioaugmentation and biostimulation approaches. Cylindrical samples of 7.5 cm height and 3.5 cm diameter were prepared. Treatment efficiency was assessed through unconfined compressive strength (UCS) and permeability tests. Moreover, calcite content was measured to evaluate calcite precipitation uniformity. The microstructural characteristics of the precipitated calcite were examined through scanning electron microscopy (SEM). The results showed that the strength and stiffness of all soil samples was considerably enhanced through both approaches, with UCS values ranging from 0.25 to 0.31 MPa for calcite contents of 4 to 6%. Notably, in some cases, the biostimulation approach yielded similar mechanical soil properties as the bioaugmentation method, indicating its potential as a sustainable alternative to bioaugmentation.