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/).

Industrial wastes cause damage to the environment and pose a threat to public health. The utilization of industrial wastes is inevitable if a circular economy needs to be achieved. Cement kiln dust (CKD) is a potential engineering material that can be used in many civil engineering works. The volume change behavior of a CKD is reported here. One-dimensional swelling and compression tests were carried out on CKD specimens to derive the compressibility parameters and coefficient of permeability. A cyclic wet-freeze-thaw-dry test was carried out to study the volume change of the material upon exposure to various seasonal climatic processes under a low surcharge pressure. The experimental results show that CKD can exhibit swelling under light loads. The correlations between plasticity properties and compressibility parameters that are applicable to fine-grained soils were found to overestimate the parameters of the CKD. The magnitudes of frost heave and thaw settlement were found to be significant, with an uprising type of movement accompanied by strain accumulation when the material was taken through several wet-freeze-thaw-dry cycles.

This study first invents a novel oedometer apparatus for clay slurry, featuring a lightweight acrylic loading cap, a noncontact laser displacement sensor, and a 1:1 dead-weight loading system to improve traditional consolidation devices. The novel apparatus is then used to examine two clays: Hong Kong Marine Deposit and Kaolin clay. The loading with a minimum stress of 0.025 kPa is applied on samples with a maximum initial water content exceeding 9 times the liquid limit. Results demonstrate the S shape compression curves influenced by initial water contents, and the power-type relationships between permeability coefficient and void ratio. Empirical equations are obtained to determine the yield stress point based on initial water content and liquid limit. Higher initial water contents increase compression parameters (e.g., recompression index, Cr; compression index, Cc; and creep index, C alpha), though Cr/Cc and C alpha/Cc are almost in the normal range. The Cc of Kaolin clay with initial water contents above 3.5 times the liquid limit is significantly relevant to effective stress. Finally, a nonlinear creep model is enhanced and integrated into the finite strain consolidation equations, effectively simulating the oedometer tests and a self-weight consolidation test of clay slurry with nonlinear consolidation characteristics.

In this study, a large number of typical laboratory tests were undertaken to characterise the soils in the Pearl River Estuary for geotechnical design of an infrastructure project. This study reinterpreted the results of the oedometer and triaxial tests within the critical state soil mechanics framework. Non-unique normal compression lines were identified in the oedometer tests, whereas unique critical state lines were identified in the triaxial tests. This indicates that the strong forms of fabric in the intact samples were more prone to be broken down by shearing than by volumetric compression. In addition, correlations between the physical and mechanical properties of estuarine soils have also been proposed. The findings of this study form a database of soil characteristics for this region. The method of obtaining soil mechanical parameters from physical and index properties can be adopted for similar projects.

This study investigated the physical and mechanical properties of Malaysian kaolin clay treated with cement using unconfined compression strength and Oedometer tests. The objective was to simulate the actual conditions of soil-cement column installation employing the deep soil mixing method with cement slurry over a 180-day period. Cement content varied between 5%, 10%, 15%, and 20%. To ensure homogeneous mixing and workability, water content was maintained between the liquid limit and twice the liquid limit. Results indicated that increasing cement content enhanced the unconfined shear strength and elasticity modulus of the stabilized soil while decreasing water content after curing. Consolidation tests revealed a diminishing slope of the void ratio curve with increasing cement content and curing time. This study further introduced precise correlations between the void ratio and compression characteristics of cement-stabilized clay, achieving high accuracy. Additionally, the research conclusively demonstrated a robust linear correlation (R2 = 0.99) between unconfined compressive strength and consolidation yield pressure.

Road infrastructure construction in developing countries such as Vietnam requires an enormous amount of natural sand. The scarcity of river sand is becoming increasingly severe, with predictions indicating a sustained drop in its supply. Hence, it is essential for the construction industry to implement a sustainable strategy by combining waste materials with abundant resources in order to effectively address this challenging situation. The objective of this study is to investigate the mechanical properties and evaluate the potential application of mixtures comprising rock quarry dust and sea sand for the roadbed layers of expressways. The researchers conducted a series of experiments, including the moisture content, specific gravity, angle of repose of material, and triaxial tests to study the composition and mechanical behaviors of mixtures at different ratios. Extensive parametric investigations in conjunction with the calibration in Plaxis' soil-test module obtain the Young's modulus E50 and confining pressure curves. Based on the assessment of materials utilized in roadbed layer of highway, as determined by the California bearing ratio (CBR) coefficient, it demonstrates that combining sea sand and quarry dust can generate the mixtures possessing appropriate properties for application in the construction of the roadbed of highway.

An updated DEM simulation scheme for clay is implemented by incorporating convex polygon shaped platelets and robust algorithm for physico-chemical-mechanical interaction between clay platelets. Clays with two typical microscopic structures, i.e., card-house structure and book-house structure, are simulated in oedometer test and triaxial compression test. Virtual Mercury Intrusion Porosimetry (MIP) and pore segmentation algorithms are utilized to extract pore statistics from the numerical samples. The simulation results and experimental results from the literature are thoroughly compared at both macroscopic and microscopic scales. It is found that the implemented DEM simulation scheme can satisfactorily reproduce the experimentally observed macroscopic behavior of clay. Especially, in triaxial compression tests, the critical state behavior, stress-dilatancy relationship and over-consolidation effects are generally consistent with existing experimental results. General consistency in pore size, orientation and shape distributions in DEM simulations and experiments can be observed. Clay platelets tend to rotate to align their normal directions along the major principal stress direction, while pores tend to align their long-axis directions in the confinement direction, leading to dynamically evolving fabric anisotropy. In the book-house structure clay, clay domains experience multiple deformation modes, including uniaxial compaction, shear distortion, spatial spin, and their combinations.