Natural marine clays exhibit distinct dynamic behavior compared to remolded counterparts due to their inherent structural properties. Dynamic and static triaxial tests were conducted on both marine clay types to evaluate stress-strain behavior, double amplitude strains, pore water pressure, and dynamic elastic modulus, as well as post-cyclic strength attenuation. The results indicate that due to the structural properties, the effective stress path of undisturbed samples is more ductile than that of remolded samples. Also, there is a clear inflection point in the strain development curve of undisturbed samples. The structure exerts a certain degree of restraint on the strain development of the undisturbed samples, and has a distinct impact on the variation of pore water pressure at varying dynamic stress levels. Both marine clay types exhibited gradual reductions in dynamic elastic modulus and marked undrained strength attenuation. Critically, the attenuation of dynamic elastic modulus in undisturbed samples aligned with post-cyclic strength loss, while remolded samples exhibited greater dynamic elastic modulus loss relative to strength degradation. These findings clarify the role of soil structure in cyclic response and strength degradation, offering insights for the long-term stability assessment of structures and disaster mitigation in marine clay engineering.

Increasing demand on clean energy leads to the expanded construction of offshore wind turbines (OWT) worldwide. Different types of foundations of OWTs includes gravity, jackets, monopiles etc. When functioning, OWTs face severe conditions with complex loadings (e.g. varying loading amplitudes and loading frequencies). In this study, the influence of the loading amplitude and loading frequency on the lateral displacement of monopiles in marine clay was investigated by conducting 1-g physical model tests at a scale of 1:30. The p-y curves at different depths were derived as well from the recorded moment distribution along the monopile. According to the results, the lateral displacement increases with the loading amplitude and frequency and the monopiles experience response of shakedown under cyclic loading. The lateral displacement after N cycles is related to the initial displacement via an extended logarithmic function. Besides, the p-y curves available in literature underestimate the soil resistance but hyperbolic functions provide comparatively closer predictions.

Due to economic and demographic growth, there is a rising demand for land reclamation in coastal cities of East and Southeast Asia. Marine clays typically play a critical role in these projects, and the deformation characteristics of marine clays become a crucial problem in terms of the quality of the subsoil conditions. The long-term loading behavior of marine clays has been studied by many researchers. However, relatively few studies have been done on the unloading behavior of these clays after preloading; and thus, the strain rate dependency on the unloading behavior of marine clays remains unclear. The aim of this study was to accumulate experimental data on the unloading behavior of marine clays and to develop a strain rate-based model for improving the accuracy of the predictions of the swelling behavior of marine clays during unloading. The authors conducted a series of constant rate of strain (CRS) consolidation tests from loading to unloading, and long-term unloading oedometer tests on Ariake clay, which is a well-known sensitive marine clay, to observe the swelling behavior during in unloading. The preloading time, corresponding to different strain rates at the end of preloading, was controlled to elucidate the effect of the stress history. Moreover, instead of parameter r ' p (preconsolidation pressure) for the normal consolidation visco-plastic behavior, the authors developed and proposed a new visco-plastic model by introducing the concept of a plastic rebound boundary and a new parameter R for swelling behavior during unloading. Parameter R represents the normalized distance from the current stress state to the plastic rebound boundary in logarithmic effective consolidation stress. Therefore, the visco-plastic model for the behavior in the loading stage was developed into the swelling visco-plastic behavior in the unloading stage for Ariake clay. Comparing the simulation and test results, the simplified visco-plastic swelling model was found to agree well with the test results. (c) 2025 Published by Elsevier B.V. on behalf of Japanese Geotechnical Society. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

An experimental study was carried out to understand the physico-chemical and mechanical properties of marine clay reconstituted with different pore fluids. Three different pore fluids namely distilled water, 0.4 M NaCl and 1.0 M NaCl solutions, and 0.4 M CaCl2 solution were used in this study. The specimens were prepared using a 1D slurry consolidation technique at 50 kPa vertical pressure. This paper mainly includes the microstructural studies conducted using Scanning electron microscopic (SEM) images and Mercury intrusion porosimetry (MIP) tests. Furthermore, cyclic triaxial and resonant column tests were carried out on the marine clay specimens reconstituted with 0.4 M NaCl and 0.4 M CaCl2 solutions subjected to different confining pressures. The experimental results illustrated that with an increase in concentration of pore fluid the cyclic properties of reconstituted Chennai marine clay increases for strain amplitude varying between 0.001 and 1%.

This study explored an integrated recycling strategy of utilising a typical excavation waste soil, completely decomposed granite (CDG), in geopolymer production as a sustainable alternative of cement for marine clay improvement. Experimental campaign was conducted to evaluate the effects of composite alkali content and sodium silicate modulus on the mechanical performance of CDG-based geopolymer paste. Test results identified an optimal sodium silicate modulus, while it was also found that the incorporation of magnesium oxide (MgO) in alkali activator could improve the general workability. Moreover, regarding the unconfined compressive strength of marine clay improved, it was demonstrated that the combination of calcined CDG and ground granulated blast furnace slag (GGBS) considerably outperformed cement at the same level of dosage. Finally, multi-criteria assessment based on life cycle analysis (LCA) demonstrated the advantage of CDG-based geopolymer compared to conventional binders, in terms of mechanical properties, environmental benefits, and economic cost.

There is a significant variability of salinity level in sensitive marine clays (SMC), which will produce an important impact on the development of mechanical characteristics in stabilized SMC. The influences of salt content (NaCl salt: 3, 10, and 20 g/L) on mechanical properties evolution of cement-stabilized SMC under different curing time (1, 7, 28, 60, and 90 days) have been experimentally investigated and modeled. The results indicate that the strength and modulus increase constantly with time but the time rates decrease. Meanwhile, the apparent improvement of strength and modulus at early age (up to 7 days) is observed. Higher NaCl content can bring a larger strength gain to stabilized SMC after same curing time and the enhancing effect of high salt contents (10 and 20 g/L) becomes more obvious with the extension of curing time. Whereas, the enhancing effect of high NaCl content on modulus is limited compared with strength. Further improvement provided by excessive NaCl salt (20 g/L) is not as effective. In addition, the predictive models have been established to quantitatively evaluate the evolution of mechanical properties in stabilized SMC with different NaCl contents. The capability of developed models has been demonstrated through the good agreement between simulated and experimental results.

The traditional vacuum preloading method of prefabricated vertical drain (PVDs) has been widely used in practical engineering. However, the serious clogging effect around PVDs in the process of vacuum-preloading reinforcement can easily lead to a series of problems such as uneven settlement and large lateral displacement of soil after reinforcement, which seriously affects the application of PVDs in marine clay foundation treatment. In this paper, the effect of combined treatment of marine clay by geotextiles and PVDs on reducing the clogging effect around PVDs was studied by laboratory model experiment. The effects of geotextiles with different diameters and spacings on the surface settlement, excess pore water pressure and lateral displacement of the reinforced soil were analysed. The experimental results show that this method has obvious help on alleviating the above problems, thus providing a reference for the application of geotextile combined with vacuum preloading method to treat marine clay foundation in engineering practice.

Energy dissipation can macroscopically synthesize the evolutions in the microstructure of the marine clay during cyclic loading. Hence an energy-based method was employed to investigate the failure criterion and cyclic resistance of marine clay. A series of constant-volume cyclic direct simple shear tests was conducted on undisturbed saturated marine clay from the Yangtze Estuary considering the effects of the plasticity index (IP) and cyclic stress ratio (CSR). The results indicated that a threshold CSR (CSRth) exhibiting a power function relationship with IP exists in marine clay, which divides the cyclic response into non-failure and failure states. For failed specimens, the development of energy dissipation per cycle (Wi) with the number of cycles (N) exhibited an inflection point owing to the onset of serious damage to the soil structure. In this regard, the energy-based failure criterion was proposed by considering the inflection point as the failure point. Consequently, a model was proposed to quantify the relationships between failure energy dissipation per cycle (Wf) [or failure accumulative energy dissipation (Waf)], initial vertical effective stress, IP, and the number of cycles to failure (Nf,E). An evaluation model capturing the correlation among CSR, IP, and Nf,E was then established to predict the cyclic resistance, and its applicability was verified. Compared with the strain-based cyclic failure criterion, the energybased failure criterion provides a more robust and rational approach. Finally, a failure double-amplitude shear strain (gamma DA,f) evaluation method applicable to marine clay in different seas was presented for use in practical geotechnical engineering.

This study investigates the geotechnical properties of soft Pak Phanang marine clay, prevalent in Nakhon Si Thammarat province, Thailand, where rapid economic development demands a comprehensive understanding for sustainable construction. Triaxial tests on undisturbed marine clay specimens with various stress histories and strain rates were conducted, focusing on over-consolidation ratios (OCRs) of 1, 2, 4, and 8. Shearing was performed at rates of 0.020%, 0.075%, 1.000%, and 8.500% per minute after K0 consolidation. The strain rates selected for this study represent specific values that have been chosen for a comprehensive exploration of Pak Phanang clay behavior under different loading conditions. The effects of stress histories on the marine clay behavior at various strain rates under K0 conditions were investigated. It is indicated that the greater strain rates under K0 conditions potentially lead to the larger undrained shear strengths and reduce pore water pressure for varied over-consolidation ratios. On the other hand, the greater over-consolidation ratios commonly result in lower shear strengths at all strain rates. Examination of pore pressure parameter at failure (Af\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${A}_{f}$$\end{document}) and secant Young's modulus reveals significant strain-rate-dependent behavior and OCR influence on the marine clay's response. Undrained shear strength increases with higher OCRs, emphasizing OCR's pivotal role. Rate effect analysis confirms undrained behavior, with a consistent 28% strength increase, regardless of OCR variations. Pore pressure responses exhibit a transition at OCR 4. Secant Young's modulus decreases with rising OCR, establishing a linear correlation with undrained shear strength.

This paper investigates the anisotropic characteristics of Champlain marine clay soil using a combination of laboratory techniques. A modified oedometer cell with a piezoelectric ring actuator technique was used to measure shear wave velocity during consolidation stages. The axisymmetric design of the oedometer allowed for the determination of shear wave velocity in both the vertical and horizontal planes. The preliminary findings reveal that the sensitive marine clay is inherently anisotropic, with lower preconsolidation pressure for horizontally consolidated specimens and faster propagation of shear waves in the plane parallel to the bedding layer. High-precision strain gauges integrated into the consolidation ring were used to evaluate horizontal stress during the one-dimensional consolidation test. The ability to determine mean effective stress enables the normalization of shear wave velocities using this stress, providing more coherent empirical correlations in terms of shear wave velocity. Scanning electron microscopy was used to examine the microstructure of clay specimens, providing qualitative and quantitative insight into the restructuring and reorientation of clay platelets under consolidation stress. The consistency of the results through both micro and macro-scale analyses confirms the reliability of the experimental approach, highlighting its potential for future studies on the anisotropy of Champlain marine clay fabrics.