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%.

It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays, including the hosted clay and sand particles. However, interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported. For this, a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions (ass), initial void ratio of hosted clays (ec0) and void ratio at liquid limit of hosted clays (ecL). The roles of ass in both the relationships of permeability coefficient of hosted clay (kv-hosted clay) versus effective vertical stress (s0v) and void ratio of hosted clay (ec-hosted clay) versus s0v were analyzed. The results show that the permeability coefficient of reconstituted sandy clays (kv) is dominated by hosted clay (kv 1/4 kv-hosted clay). Both ass and ec0 affect the kv of sandy clays by changing the ec-hosted clay at any given s0v. Due to the partial contacts and densified clay bridges between the sand particles (i.e. structure effects), the ec-hosted clay in sandy clays is higher than that in clays at the same s0v. The kv - ec-hosted clay relationship of sandy clays is independent of ec0 and ass, but is a function of ecL. The types of hosted clays affect the kv of sandy clays by changing the ecL. Based on the relationship between permeability coefficient and void ratio for the reconstituted clays, an empirical method for determining the kv is proposed and validated for sandy clays. The predicted values are almost consistent with the measured values with kv-predicted=kv-measured 1/4 0.6-2.5. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

This study conducted a series of cyclic and monotonic triaxial tests on reconstituted landfill waste material from a closed landfill site in Sydney, Australia, to assess its dynamic behaviour under various testing conditions. Specifically, the effects of cyclic deviatoric stress, loading frequency, and effective confining stress on the cumulative plastic axial strain, resilient modulus, and damping ratio under undrained cyclic loading conditions were investigated. Results indicated that the plastic deformation, resilient modulus, and material damping are significantly influenced by dynamic stress and confining stress, with a lesser impact from loading frequency. Notably, as the number of loading cycles increased, the cumulative plastic axial strain and resilient modulus exhibited an increase, whereas the damping ratio decreased. Furthermore, increasing cyclic deviatoric stress led to an increase in both cumulative plastic axial strain and damping ratio, while an increase in confining stress resulted in a decrease in these parameters. Conversely, the resilient modulus showed an increase with rising cyclic deviatoric stress and confining stress. The influence of loading frequency on cumulative plastic axial strain and resilient modulus was minor, and its effect on the damping ratio was rather negligible. The study observed that initial loading cycles caused rearrangement and reorientation of waste components and the mobilisation of fibres with tensile forces as loading progressed, suggesting that these landfill waste samples behaved comparably to fibrous soil with randomly distributed fibres. Through nonlinear regression analysis, an empirical relationship for cumulative plastic axial strain incorporating cyclic deviatoric stress, confining stress, number of cycles, and frequency was derived. This research contributes valuable insights into the behaviour of compacted landfills as railway subgrades, providing a foundation for informed decision-making in the design of transport infrastructure over closed landfill sites.

Three soft rock facies of the Middle Globigerina Limestone (MGL) from Malta, of mineralogical composition and index properties similar to some medium -high density Chalk facies, are disaggregated through prolonged agitation in water to create reconstituted samples. The significant activity of their clay-sized calcite grains can impart a medium -high plasticity. Scanning electron microscopy analyses of natural and reconstituted samples show the natural bonding as interlock, possibly induced by cohesive clay-sized calcite grains during the sediment compaction. Micro-analyses and compression test data also show that local calcite crystal overgrowth under burial has reduced further the soft rock porosity, making it lower than that of the reconstituted material one-dimensionally compressed to the geological preconsolidation pressure. Nonetheless, the low stress sensitivity of natural MGL suggests that this interlock bonding does not strengthen much the material with respect to the highly compressed reconstituted soil. The natural MGL is of very low permeability, which reduces further with compression. Concurrently, the soft rock creep coefficient increases, reaching values far above those typical for clays. The microstructural features and the mechanical properties of the different MGL facies are shown to be sensitive to clay mineral content.

Due to the long-term deformation settlement of foundations, issues such as damage and functional failure of buildings and structures have long been a concern in the engineering field. The creep of soil is one of the primary causes leading to long-term deformation of foundations. In this paper, the consolidation deformation, creep characteristics, and creep model of reconstituted saturated silty clay were studied using the isotropic consolidation creep test and triaxial compression creep test. The results show that for the isotropic consolidation creep test, although the applied load adopted different stages of loading, as long as the final applied confining pressure was the same, the number of stages applied by the confining pressure had little effect on the final isotropic consolidation deformation of the sample and the triaxial undrained shear strength after creep. However, for the triaxial shear creep test, it was found that under the same final deviatoric stress, the final deviatoric strain of the sample was closely related to the number of loading stages of deviatoric stress. The test showed that the more loading stages with the same deviatoric stress, the smaller the final deviatoric strain, and the triaxial undrained shear strength of the sample after creep increased. In addition, it was reasonable to set the pore pressure dissipation of the sample at 95% ((u0 - u)/u0 = 95%) as the time (t100) at which the primary consolidation of the soil sample was completed. The isotropic consolidation creep curves and the triaxial compression creep curves showed certain non-linearity. Then, the logarithmic model and the hyperbolic model were used to fit the creep curves of the samples. It was found that the hyperbolic model had a better fitting effect than the logarithmic model, but for the triaxial compression creep test, the creep parameters of the sample changed greatly. Therefore, studying the creep characteristics of soil under different pre-loading steps is of significant engineering importance for evaluating the long-term deformation of underground structures.