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Clay swell potential can be classified based on the value of activity and it is defined as the ratio of plasticity index to clay content as a percentage. This paper outlines the investigation into how activity correlates with other key properties of clayey soils. Specifically, four approaches were evaluated for predicting activity using: (a) liquid limit (LL), specific surface area (SSA), cation exchange capacity (CEC) and clay content; (b) LL, SSA and CEC; (c) LL; and (d) SSA and CEC. For this purpose, a database of 104 samples was collected from which 35 machine learning algorithms were trained. Gradient Boosting Trees showed the highest prediction accuracy in the four approaches and, to improve its prediction performance, a Bayesian Optimization was applied to tune theirs hyperparameters, resulting in the final models. The performance of the developed models was evaluated, showing prominent results with exceptionally good metrics, except in the approach from SSA and CEC where the trained algorithm was not capable of predicting activity with confidence (R2=0.46). This algorithm can predict activity using only LL with high accuracy (R2=0.94), and when combined with SSA and CEC, the precision is further enhanced (R2=0.96). [ABSTRACT FROM AUTHOR]

AbstractDamping plays a crucial role in the design of offshore wind turbine (OWT) monopile foundations. The soil damping of the monopile-soil system (MSS) represents the energy dissipation mechanism arising from the interaction between the pile and the soil. It is typically derived by back-calculating from the overall damping measured in the entire OWT structure. However, few studies have independently examined the soil damping in MSS, and the impact of key parameters such as pile diameter, pile embedded depth, cyclic load amplitude, and load eccentricity on the variation of soil damping in MSS remains unclear. This paper introduces an elastoplastic-damage constitutive model for the numerical simulation of the damping ratio variation in seabed soil and MSS. The model is implemented in ABAQUS software and validated against cyclic triaxial tests on stiff clay soil. On this basis, a three-dimensional finite element sensitivity study was conducted to elucidate the effect of these key parameters on the MSS damping ratio. The results of the study reveal that the MSS damping ratio exhibits a nonlinear and asymmetric trend as the loading cycles increase. The MSS damping ratio decreases with increasing pile diameter and embedded depth but increases with increasing lateral cyclic load amplitude and load eccentricity from the mudline. [ABSTRACT FROM AUTHOR]

Three quarters of the world's significant urban centers are located in coastal regions where clay minerals are prevalent. The microstructures and physico-mechanical properties of clay sediments are highly susceptible to alterations in pore water chemistry. The pore water chemistry in soil changes easily due to groundwater pollution, seawater erosion, degradation, etc. However, there are several inconsistencies in the literature on the change of physical and mechanical properties of clay soils caused by the change of pore water chemical properties, i.e., disparate experimental results were reported for the same soil property, or varying explanations were proposed for the identical experimental results. Currently, the research in this field mainly focuses on the macroscopic behavioral modifications while lacking the explanations of microscopic mechanism. Therefore, this paper presents a comprehensive review of researches conducted over the past four decades on the impact of pore water chemistry (including salt type, salinity, ion valence, pH) on soil properties such as the microstructure, settlement, Atterberg limits, shear strength, conductivity, unsaturated soil mechanics properties and thermal properties. The fundamental mechanisms underlying the varied experimental observations on clay sediments affected by salt and pH are systematically explored, and deficiencies in this field are identified. The observed dispersion in the literatures is attributed to the spatial variation and heterogeneity of soil compositions, different test methods, and insufficiency of the fundamental microscopic mechanisms of the observed soil behaviors, etc. Therefore, it is necessary to further explore the essential mechanisms of the test results in the future to establish a unified conclusion. [ABSTRACT FROM AUTHOR]