Expansive soil, characterized by significant swelling-shrinkage behavior, is prone to cracking under wet-dry cycles, severely compromising engineering stability. This study combines experimental and molecular dynamics (MD) simulation approaches to systematically investigate the improvement effects and micromechanisms of polyvinyl alcohol (PVA) on expansive soil. First, direct shear tests were conducted to analyze the effects of PVA content (0 %-4 %) and moisture content (30 %-50 %) on the shear strength, cohesive force, and internal friction angle of modified soil. Results show that PVA significantly enhances soil cohesive force, with optimal improvement achieved at 3 % PVA content. Second, wet-dry cycle experiments revealed that PVA effectively suppresses crack propagation by improving tensile strength and water retention. Finally, molecular dynamics simulations uncovered the distribution of PVA between montmorillonite (MMT) layers and its influence on interfacial friction behavior. The simulations demonstrated that PVA forms hydrogen bonding networks, enhancing interlayer interactions and frictional resistance. The improved mechanical performance of PVAmodified soil is attributed to both nanoscale bonding effects and macroscale structural reinforcement. This study provides theoretical insights and technical support for expansive soil stabilization.

The breakage phenomenon has gained attention from geotechnical and mining engineers primarily due to its pivotal influence on the mechanical response of granular soils. Numerous researchers performed laboratory tests on crushable soils and incorporated the corresponding effects into numerical simulations. A systematic review of various studies is crucial for gaining insight into the current state of knowledge and for illuminating the required developments for upcoming research projects. The current state-of-the-art study summarizes both experimental evidence and numerical approaches, particularly focusing on discrete element simulations and constitutive models used to describe the behavior of crushable soils. The review begins by exploring particle breakage quantification, delving into experimental evidence to elucidate its influence on the mechanical behavior of granular soils, and examining the factors that affect the breakage phenomenon. In this context, the accuracy of various indices in estimating the extent of breakage has been assessed through ten series of experiments conducted on different crushable soils. Furthermore, alternative breakage indices are suggested for constitutive models to track the evolution of particle crushing under continuous shearing. Regarding numerical modeling, the review covers different approaches using the discrete element method (DEM) for simulating the behavior of crushable particulate media, discussing the advantages and disadvantages of each approach. Additionally, different families of constitutive models, including elastoplasticity, hypoplasticity, and thermodynamically based approaches, are analyzed. The performance of one model from each group is evaluated in simulating the response of Tacheng rockfill material under drained triaxial tests. Finally, new insights into the development of constitutive models and areas requiring further investigation utilizing DEM have been highlighted.

As offshore wind turbines approach the end of their operational lifespan, the decommissioning process is gaining increasing importance, which highlights the need to develop expertise in the marine operations involved in this task. This study focuses on simulating the vibratory extraction of a monopile foundation for an offshore wind turbine using a crane barge. A numerical model is developed to couple the dynamic behavior of the monopile with that of the barge. To accurately represent soil behavior during the extraction process, a high-fidelity finite element model is first established to calculate the soil resistance component under high-frequency cyclic loading generated by the vibro-hammer. Then, time domain numerical simulations of the monopile decommissioning process are carried out, and an external Dynamic Link Library (DLL) is developed to integrate this soil resistance force into the time-domain program. Additionally, the centrifugal force exerted by the vibro-hammer is incorporated into the model through a separate DLL. Time-domain simulations are performed to analyze the barge's motion and the tension in the lifting wire under calm water conditions. These results are then compared with simulations conducted under long-crested waves to provide a comprehensive understanding of the extraction process. This study also examines the effect of the dynamic positioning system on the barge's dynamic response and the tension in the lifting wire. The outcome of this paper contributes to a better understanding of the complex decommissioning process under marine environments.

Earthquake induced soil liquefaction poses a significant threat to buildings and infrastructure, as evidenced by numerous catastrophic seismic events. Existing approaches of regional liquefaction hazard assessment predominantly rely on deterministic analysis methods. This paper presents a novel Probabilistic Liquefaction Hazard Analysis (PLHA) framework based on Monte-Carlo (MC) simulations to mitigate future seismic risks associated with liquefaction. The proposed procedure requires only publicly available data, offering accessibility and applicability in resource-constrained settings. A key feature of the procedure is its ability to deal with uncertainties in earthquake and soil parameters using distribution functions. Liquefaction potential is assessed through parameters such as Liquefaction Potential Index (LPI\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$LPI$$\end{document}) and Liquefaction Severity (LS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${L}_{S}$$\end{document}). The procedure is implemented in MATLAB as part of a broader probabilistic risk assessment framework for developing countries. The developed procedure is applied to the high risk city of Adapazari, T & uuml;rkiye; an area lacking prior PLHA studies. Results are validated against observed liquefaction data from a simulated scenario event of the 1999 Kocaeli earthquake. Probabilistic liquefaction hazard maps are generated for the study area and the entire Marmara region in terms of LPI\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$LPI$$\end{document} and LS\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${L}_{S}$$\end{document}. A novel aspect of this work is the integration of a time-dependent Probabilistic Seismic Hazard Analysis (PSHA) model into the PLHA framework. Results are compared with those predicted using the Poisson model for the Marmara region. Findings demonstrate that the developed PLHA procedure offers a robust and flexible tool for predicting seismic liquefaction hazards, providing valuable insights for loss estimation and risk mitigation planning.

In this study, a series of undrained multidirectional cyclic simple shear tests were conducted using the discrete element method. Various stress paths, including figure-8, circular, teardrop, and straight-line shapes, were considered. Realistic and irregular particles were generated by integrating the theory of random fields for spherical topology with the Fourier-shape-based method. The influence of particle shape irregularity was assessed using a synthetic parameter derived from four common descriptors: aspect ratio, roundness, convexity, and sphericity. The study revealed that the liquefaction resistance of samples subjected to a constant cyclic shear stress ratio predominantly depended on the stress trajectory and particle shape. Numerical results demonstrated that the sample undergoing the unidirectional simple shear exhibited the highest liquefaction resistance, whereas the figure-8 shape exhibited the lowest. Furthermore, greater irregularity in particle shape corresponded to increased resistance to failure. Additionally, microstructural evolutions of granular samples were quantified throughout the simulation using the contact-normal-based fabric tensor. This allowed for a comprehensive exploration of the interplay between internal structure and external loading, leading to a more comprehensive understanding of the macroscopic observations discussed above.

Among the techniques used to control or mitigate the structural vibrations induced by dynamic input, such as wind and earthquake, the dissipative coupling is one of the most applied, especially for its ease of implementation. Indeed, for example in large urban areas, it is common to find adjacent structures where the space between the buildings becomes smaller. To optimally select the visco-elastic features of the dissipative device to be used, the paper retraces the path followed by the previous scientific works proposing new design criteria. Such criteria are based on the nonlinear stochastic response of two simple oscillators linked by a damper whose hysteretic behavior is represented by a Bouc-Wen model. A state-space formulation of the equations of motion has been adopted to facilitate the analysis of the dynamic response. At the same time, the loading is hypothesized as a zero-mean Gaussian excitation. Consequently, the nonlinear response has been approximately evaluated by the equivalent linearized standard deviations for both displacements and accelerations. Subsequently, formulations of objective functions, based on the Minimax and Total Energy of the equivalent linearized stochastic response, have been applied to determine the optimal configurations of the coupled system. The influence of both noise power amplitude and soil typology on the designed systems has been also investigated. Suggestions related to the path to achieve pre-fixed targets (as balancing of displacements and accelerations) are provided.

The development of biodegradable slow-release fertilizers derived from lignocellulosic materials is essential for mitigating environmental pollution and ecological damage associated with petroleum-based components in conventional fertilizers, as well as for enhancing agricultural productivity. In this study, a Camellia oleifera Abel. shell based slow-release fertilizer (COSU) was prepared by molten urea impregnation method. FTIR NMR, SEM, EDX, BET and molecular dynamic simulation were used to reveal the urea storage and slow-release mechanisms of COSU at the cell wall and molecular level. These results indicated the role of the cellular tissue structure with its pore structure in the storage and slow release of urea and demonstrate the molecular behavior of urea adsorption and release on lignocellulosic chemical component. The maximum nitrogen loading rate of COSU was 36.58 % and the cumulative release rate over 28 days was 75.08 %, which met the GBT23348-2009 standard. The multiple coupling regulatory mechanism of the cell wall - lignocellulosic molecules of urea store and releasing were discussed and proposed. Pot experiments confirmed that the prepared slow-release fertilizer not only stimulated the growth of corn seedlings but also contributed to an increase in soil humus. The findings of this research provide a new insight and a solid theoretical foundation for the development of lignocellulose-based slow-release fertilizers, offering a sustainable alternative to traditional fertilizers and contributing to a greener agricultural future.

Debris flows are a dynamic and hazardous geological phenomenon, as by definition, debris flows are rapid, gravity-driven flows of saturated materials that often contain a mixture of water, rock, soil, and organic matter. They are highly destructive and occur in steep channels, posing a significant threat to infrastructure and human life. The dynamics of debris flows are complex due to their non-Newtonian behaviour and varying sediment-water interactions, making accurate modelling essential for risk mitigation and emergency planning. This paper reports and discusses the results of numerical simulations of back analyses aimed at studying the reconstruction of a real rapid debris flow. The selected test case is the event that occurred on 12 and 16 March 2021 along the Rio Sonno channel, a tributary of the Liri River, following the landslide event of Rendinara (Municipality of Morino, Abruzzo Region, Italy). There are significant flow sources in the area, fed by a highly fractured carbonaceous aquifer that extends immediately upslope of the detachment zone. The continuous flow influences the saturation level in the fine-grained sediments and favours the triggering of the debris flow. This phenomenon was simulated using the commercial RAMMS code, and the rheological model selected was Voellmy fluid friction. The modelling approaches used in this research are valid tools to estimate the volumes of materials involved in the flow-feeding process and for the purpose of possible mitigation works (debris flow-type dams, weirs, flow diversion, etc.).

The discrete element method (DEM) is used to simulate the behavior of a model sand under cyclic stress. Two approaches are employed in the contact model to account for the effect of anisotropic particle shape: (1) spheres with a rolling resistance moment and (2) clumps of spheres. Model parameters are calibrated using experimental results from drained monotonic triaxial tests on NE34 sand. Then, a series of cyclic triaxial tests is done on a homogeneous elementary volume sample with varying density index (ID\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$I_D$$\end{document}) and cyclic stress ratio (CSR). Both macroscopic and micromechanical characteristics of the material are examined under cyclic loads. In particular, the evolution of Young's modulus (E) and the damping ratio (D) with strain amplitude are evaluated at varying ID\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$I_D$$\end{document} and compared with values from the literature. An analysis of the coordination number (Z), orientation of strong and weak contact forces, friction mobilization, sliding contacts and fabric evolution links the observed macroscopic behavior of energy dissipation to the phenomenon of frictional sliding at the grain scale.

Between 1925 and 1930, 11 or 12 non-native mountain goats (Oreamnos americanus) were translocated from Alaska and British Columbia to the foothills of the Olympic Range. By 1970, descendants of these goats had colonized the entire range and concerns about the management of this introduced species developed as damage to alpine soil and vegetation occurred. A series of removals reduced the population from 1175 in 1983 to 389 by 1990, eventually growing to 584 in 2016. We used demographic and genetic data to parameterize a population genetics individual-based simulation model of the Olympic Range mountain goats. We calibrated the model to replicate the population trajectory for Olympic mountain goats from establishment in the 1920s through the 1983 first census. As expected, modeled population dynamics from 1928 to 1983 mimicked parameter initialization from expanding populations. However, simulated heterozygosity did not align with observations, suggesting a process not accounted for within the simulation model, such as a bottleneck or founder effect. Sensitivity analyses showed changes in annual reproductive rate, juvenile mortality, and adult female mortality influencing population trajectories, but variation in male mortality revealed no changes. Evaluating the population dynamics of the model after removals showed that approximately 80% of the total animals removed during the 1980s needed to be female in order for the observed population estimates to occur. This model has the potential to be used more widely with established or introduced mountain goat populations, as well as to provide an approach for studying other introduced species and their population dynamics.