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Use of helical piles has become increasingly popular since last few decades for numerous advantages and installation convenience. They may consist of isolated helical plate welded to a central shaft or continuous screw type piles. The load transfer mechanism of helical piles is complex compared to the conventional vertical driven piles. Although limited contributions are available on the performance of helical piles including theoretical and experimental studies, still there are major scopes for further research. The authors have conducted a series of laboratory experimentations on axial load-settlement characteristics of model helical piles made of high tension steel in soft clayey soil, followed by 3D finite element analysis using ABAQUS. The numerical results were found to be close to the experimental observations. Using the numerical model, extensive parametric studies were conducted. The load-settlement response was found to be mostly logarithmic. The pile capacity was found to be influenced significantly by the pitch and embedded pile length. The FEM analysis revealed maximum plastic strain and displacement to develop adjacent to the pile-tip and the interface, while negligible at the boundaries. The interface shear stress distributions are also studied. From the entire investigation, a set of important conclusions are drawn. [ABSTRACT FROM AUTHOR]

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]

In recent times, large-scale infrastructural projects are being constructed on varieties of soil, especially in highly compressible marine clays and soft soil. The coefficient of consolidation (cv) is one of the most important technical parameters used to estimate the consolidation characteristics of the soil. The experimental laboratory techniques used to obtain cv are time-consuming and possess different practical limitations. In this study, a reliable method for predicting cv is presented based on machine learning (ML). The study considered 11 inherent soil variables, among which the least significant variables are discarded using univariate feature selection technique. Different ML models were developed like the random forest, artificial neural network, and support vector machine for nonlinear mapping of the cv using dimensionally reduced independent variables. Verification against experimental data demonstrates that the Random Forest model accurately predicts the cv (with MAE = 0.0231, MSE= 0.00148, and RMSE = 0.03854). Further, a comparative study of the proposed model is presented with available empirical equations and numerically simulated data. Moreover, the strengths and shortcomings of different ML algorithms are also discussed in detail. [ABSTRACT FROM AUTHOR]

Suction bucket installation in pure clay or pure sand is well established. However, in layered soils, particularly in sand over clay soils, the soil plug uplift is considered a major installation risk and feasibility of installation is often questioned. In this paper, the experience from installation of two suction bucket jackets at two offshore wind farms in layered soils is reported. The installation at both sites was successful and no excess plug uplift was observed. The transfer of suction to the clay-sand interface is believed to have contributed to the success of the installations. The two cases presented in this paper provides confidence in suction bucket foundation installation in similar soil conditions. [ABSTRACT FROM AUTHOR]

This research investigates the shrinkage behaviour of clay specimens subjected to different hydraulic paths. The volume change and microstructure of desiccated clay specimen directly dried from reconstituted slurry and compacted states, and the desiccated clay specimens obtained by subjecting the as-compacted clay specimen to cyclic wetting and drying process were compared. The experimental results showed that the initial microstructural difference between reconstituted slurries and compacted specimens influences their shrinkage behaviour. The compacted clay specimens retained the bimodal structure even after subjecting to cyclic wetting and drying, unlike the reconstituted slurry, which showed a predominant unimodal structure at the end of drying process. This is due to the absence of large macropores in the desiccated clay specimen dried from reconstituted slurry state, which is evidenced from the mercury intrusion porosimetry studies, scanning electron microscopy and nano-focus X-ray-computed tomography imaging experiments. [ABSTRACT FROM AUTHOR]

Analysis and design with simple correlations are always of interest to engineers. Predicting the bearing capacity of a spudcan in a multi-layered clay soil is one of the challenges facing jack-up designers and the installation process. In this paper, simple correlations are presented for the prediction of the bearing capacity–penetration curve of the spudcan using numerical modeling results and analyzing the parameters affecting the bearing capacity of a spudcan in a multi-layered clay soil. Multivariate regression was used to obtain these correlations and their quality was evaluated by comparing the numerical modeling results to the prediction correlations. Moreover, some examples were solved using data obtained from previous research and the resultant curves were compared with the reference curves. The results showed that the presented correlations had good accuracy in predicting the bearing capacity of spudcans in various profiles of multi-layered clay soils. [ABSTRACT FROM AUTHOR]

The Yellow River Delta is one of the most abundant offshore energy areas in China, and the construction of offshore projects is rapidly developing. In this paper, four typical regions of the Yellow River Delta in different periods were selected as research objects. In-situ cone penetration tests (CPTs), geotechnical testing, electron microscope scanning testing, and soil type indexing (Ic) was used to classify and identify the soil layers. At the same time, a modified calculation model based on CPT for the shear wave velocity of fine-grained seabed soil was sought and verified with the measured values. The results showed that: (1) the obtained soil layers are mainly classified by clay and silty soil, which is in line with the conclusions of previous scholars on the classification of the Yellow River Delta soil layer. (2) The measured shear wave velocity is generally between 100 m/s and 250 m/s, and it gradually increases with depth. (3) The depth, cone resistance, and soil behavior index are directly related to the calculation of the shear wave velocity in this area. (4) Discrete analysis of measured and calculated shear wave velocity provides theoretical support for the change of shear wave velocity under different conditions. [ABSTRACT FROM AUTHOR]

MgCl2 is widely used on roads for controlling dust and humidity, reducing the scattering of coarse particles, anti-icing, and improving the geotechnical properties of "problematic soils" by chemical stabilization. In this study, we initially induced the MgCl2 solution to electrokinetic stabilization. Six electrokinetic experiments were conducted on marine clayey soil, collected from Zhuhai, China, to investigate the feasibility using MgCl2 solution as a green stabilizer in the electrokinetic stabilization process. The dewatering efficiency, unconfined compressive strength (UCS), anode corrosion and power consumption due to electrokinetic treatment were analysed. Up to 600% increases in UCS taken from the anode zones was observed after 7-days of curing. The results revealed that injecting of 0.8% MgCl2 solution (by the dry wight of soil) at a constant concentration of 20% was the optimum amount for the electrokinetic stabilization of marine clayey soil from Zhuhai, and the higher concentration of MgCl2 solution reduced the degree of anode corrosion. [ABSTRACT FROM AUTHOR]

Geosynthetic-encased stone column (GESC) has been proved as an effective alternative to reinforcing soft marine clay soils with low undrained shear strength. In this paper, three-dimensional (3-D) coupled mechanical and hydraulic modeling based on centrifugal model test was carried out to investigate the performance of GESC-supported embankment over soft clay with two different stiffness of encasement (i.e., 450 kN/m and 3300 kN/m). The numerical modeling results agree well with the centrifugal model test recordings. This investigation reveals that with the increase in the geogrid stiffness the differential settlement between the GESC and the surrounding soft marine clay soil was found to increase. Under the embankment load, the encased columns located below the embankment slope have experienced significant vertical and lateral stress ratio. Moreover, columns below the embankment slope tend to experience significant hoop strain below the top of the column. [ABSTRACT FROM AUTHOR]