The solidification of dredged marine sediments with high water content is important for maintenance dredging and reclamations. To reduce the carbon emission of solidification, low-carbon recycled wastes such as incinerated sewage sludge ash (ISSA) and ground granulated blastfurnace slag (GGBS) have been recently adopted as binding materials to replace conventional Portland cement. For soil slurry with ultra-high water content, using the consolidationsolidification combined method is an effective way to reduce the volume and improve the final mechanical properties. However, it is unclear how the consolidation interacts with solidification using the binding materials. In this study, a series of laboratory tests were conducted on dredged Hong Kong marine deposit slurry mixed with ISSA and GGBS with alkali activation by lime. The elemental consolidation tests controlled with different constant rates of strain and multistage loadings demonstrate that the rate of consolidation has significant effects on volume reduction and yielding stress development during consolidation-solidification treatment. Consolidationsolidification achieves higher volume reduction and yielding stress than pure solidification. As the rate of consolidation decreases, there is a smaller volume reduction at the same effective stress and less yielding stress enhancement at the same curing time. A scanning electron microscope with energy dispersive spectrometer was used to investigate hydration products and soil fabric after treatment. The slower rate of consolidation causes the looser structure and finer needleshaped products with the same curing period, which can explain the mechanical properties observed from the element tests.

Estimating the spatial distribution of hydromechanical properties in the investigated subsoil by defining an Engineering Geological Model (EGM) is crucial in urban planning, geotechnical designing and mining activities. The EGM is always affected by (i) the spatial variability of the measured properties of soils and rocks, (ii) the uncertainties related to measurement and spatial estimation, as well as (iii) the propagated uncertainty related to the analytical formulation of the transformation equation. The latter is highly impactful on the overall uncertainty when design/target variables cannot be measured directly (e.g., in the case of piezocone Cone Penetration Test-CPTu measurements). This paper focuses on assessing the Propagated Uncertainty (PU) when defining 3D EGMs of three CPTu-derived design/target variables: the undrained shear resistance (su), the friction angle ((p'), and the hydraulic conductivity (k). We applied the Sequential Gaussian Co-Simulation method (SGCS) to the measured profiles of tip (qc) and shaft resistance (fs), and the pore pressure (u2), measured through CPTus in a portion of Bologna district (Italy). First, we calculated 1000 realizations of the measured variables using SGCS; then, we used the available transformation equations to obtain the same number of realizations of su, (p', and k. The results showed that PU is larger when the transformation equation used to obtain the design/target variable is very complex and dependent on more than one input variable, such as in the case of k. Instead, linear (i.e., for su) or logarithmic (i.e., for (p') transformation functions do not contribute to the overall uncertainty of results considerably.

Deep cement mixing (DCM) is a popular in situ soil stabilization method, while the investigation on long-term coupled consolidation and contaminant leaching behavior of cement-stabilized contaminated soil is limited. In this study, axisymmetric physical model tests were conducted to investigate the coupled behaviors of a composite ground, which consisted of a central column made of cement-stabilized arsenic-contaminated marine deposits and surrounding untreated marine deposits. The test results revealed the settlement development of composite ground and the mechanism of load transfer between the DCM column and surrounding soils with increasing loading. The presence of arsenic decreased the strength and stiffness of the DCM column through the reaction between arsenic and hydration and pozzolanic reaction products. With the increase of the water/cement ratio in the DCM column, the concentration level of arsenic in the draining-out water of the composite ground increased significantly, while that in the surrounding soil showed no obvious change, indicating that arsenic mainly migrated directly through the DCM column. A theoretical axisymmetric consolidation model coupling solute transport for composite ground was established and subsequently applied to analyze the test data. The numerical model accurately depicted the pore water pressure, settlement, and spatiotemporal distribution of arsenic concentration in the physical model.

Liquefaction behaviors of sand deposits with impervious stratum are quite different from that of homogeneous geological conditions. However, the micro- liquefaction behaviors of the interlayered deposits have been infrequently documented. This study introduces a novel experimental methodology aimed at examining the influence of silt interlayer on the liquefaction mechanisms of sand deposits from both macro and micro perspectives. In the experiments, the Excess Pore Water Pressure (EPWP) was analyzed in conjunction with recorded micro liquefaction images. The migration mechanism of fine sand particles beneath the silt interlayer was revealed. The existence of low permeability interlayer leads to prolonged retention of EPWP beneath the silt interlayer. Substantially, the water film on the base of the interlayer is demonstrated to be the mixture of pore water and silt particles flowing with high velocity under seismic motions, thereby resulting in significant strain localization. An agminated zone of loose fine sand particles is usually generated beneath the silt interlayer after the dissipation of EPWP.

Most natural granular deposits are spatially variable due to heterogeneities in soil hydraulic conductivity, layer thickness, relative density, and continuity. However, existing simplified liquefaction evaluation procedures treat each susceptible layer as homogeneous and in isolation, neglecting water flow patterns and displacement mechanisms that result from interactions among soil layers, the groundwater table, foundation, and structure. In this paper, three-dimensional, fully coupled, nonlinear, dynamic finite-element analyses, validated with centrifuge experimental results, are used to evaluate the influence of stratigraphic layering, depth to the groundwater table, and foundation-structure properties on system performance. The ejecta potential index (EPI) serves as a proxy for surface ejecta severity within each soil profile. The results reveal that among all the engineering demand parameters (EDPs) and geotechnical liquefaction indices considered, only EPI predicted a substantial change in the surface manifestation of liquefaction due to changes in the location of the groundwater table and soil stratigraphy. This trend better follows the patterns from case history observations, indicating the value of EPI. Profiles with multiple critical liquefiable layers at greater depths resulted in base isolation and reduced permanent foundation settlement. Ground motion characteristics have the highest influence on EDPs, among the properties considered. The outcropping rock motion intensity measures with the best combination of efficiency, sufficiency, and predictability were identified as cumulative absolute velocity (for predicting foundation's permanent settlement and free-field EPI) and peak ground velocity (for peak excess porepressure ratio). These results underscore the importance of careful field characterization of stratigraphic layering in relation to the foundation and structural properties to evaluate the potential liquefaction deformation and damage mechanisms. The results also indicate that incorporating EPI alongside traditional EDPs shows promise.

Rainfall has been recognized as a key factor in triggering landslides. However, it is not entirely clear why many landslides have been triggered by slight-to-moderate rainfall. The Mudui landslide that occurred in Sichuan Province, China, on June 22, 2020, exemplifies the evolution of landslides induced by seasonal rainfall, which can cause substantial damage to infrastructure. This landslide was a deep-seated debris slide with a volume of approximately 0.64 million m3. It occurred in colluvial deposits, which are heterogeneous soil-rock mixtures with high permeability that easily retain water. On the basis of detailed site investigations and various monitoring data-including interferometric synthetic-aperture radar (InSAR), ground-slope and subsurface-slope deformation monitoring, and hydrogeological monitoring-we investigated the landslide-triggering mechanism along with pre- and post-landslide kinematics and assessed the effects of remedial works. The results show that both the soil water content and the slope deformations have significant seasonal characteristics. The soil water content decreases during dry seasons and increases during rainy seasons. Correspondingly, the deformation rates increase with the onset of rainy seasons and decrease with the onset of dry seasons. The landslide area underwent progressive deformations linked to groundwater seepage, inducing a continuous deterioration of the soil body. Finally, prolonged rainfall triggered the landslide of the deteriorated soil mass. The results indicate that the adverse effects of long-term seasonal soil-water-content fluctuations need to be take into account in analyzing slope instabilities in colluvial deposits.

This study aims to evaluate the possibility of reusing treated marine clayey soils by stabilization/solidification (S/S) technology as geomaterial in reclamation projects from the aspects of engineering strength, chemical modification and environmental risk assessment. The lime-activated incinerated sewage sludge ash (ISSA) together with ground granulated blast furnace slag (GGBS) was employed as the binder. The multi-controlling factors including water content, curing time, salinity, and chemical compositions of mixing solution were taken into account to identify the S/S treated Hong Kong marine deposit (HKMD) slurry based on the strength tests, pH measurement, thermo-gravimetric (TG) analysis, X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS) and toxicity characteristic leaching procedure (TCLP) tests, etc. The results show that the S/S treatment using lime-activated ISSA-GGBS can effectively enhance the strength of marine soil at the initial water content of 110% and 200%. The water content and curing time have a significant impact on the S/S treated HKMD. The pH of treated soils is higher than 11.1, which proves an alkaline environment for the reactions in the treated soil. A special case is the treated HKMD at 200% water content hydrated by MgCl2 solution, which has a low pH of 10.23 and maintains a slurry state. Based on the TCLP results, the leaching concentration of heavy metals from S/S treated HKMD is environmentally safe and meets Hong Kong standard for reusing treated soil with a low level of <0.2 mg/L. The content of main products such as calcium/magnesium silicate hydrate, ettringite or Friedel's salt depends on the chemical additions (e.g. distilled water, seawater, NaCl and Na2SO4). The products in the specimens mixed with MgCl2 solutions are mainly composed of Mg(OH)(2), M-S-H and MgCO3, which is distinct with the neoformations in the other cases. Therefore, this study proves that the S/S treated soil slurry could be reused as geomaterials in reclamation projects, and the S/S process is greatly affected by water content, curing time and solution compositions, etc. (c) 2024 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/).

Slope failures are a significant natural geohazard in hilly and mountainous regions, often resulting in loss of life and infrastructure damage. The Muketuri-Alem Ketema road in Ethiopia is particularly vulnerable to landslides due to colluvial deposits on steep slopes from the higher northeastern plots to the lower Jemma River valley. This study investigates the characteristics of colluvial soil and evaluates the stability of slopes prone to landslides. It combines geophysical data, penetrometer tests, laboratory analyses, Google Earth images, and detailed field visits to assess the soil and bedrock composition and structure. Numerical methods, including limit equilibrium (Bishop, Janbu, Spencer, and Morgenstern-Price methods) and finite element methods, were used to analyze slope sections under various saturation conditions and simulate different rainfall patterns. The results indicate that the Bishop, Morgenstern-Price, and Spencer methods produce similar safety factors with minimal differences (<0.3%), while the Janbu method shows more significant variation (1.5%-5.6%). Safety factor differences for sections A-A and B-B range from 5.26% to 9.86% and 3.5%-4.7%, respectively. Simulations reveal that short-term saturation significantly reduces the stability of the upper slope layer by 20%-46.76%, and long-term saturation decreases the entire slope by 26.81%-46.76% compared to dry conditions due to increased pore water pressure and self-weight. Long-term saturation effects, combined with dynamic loads, can further reduce colluvial soil stability by over 50% compared to a dry static state. The finite element method predicts larger failure zones than limit equilibrium methods, emphasizing the need for accurate predictions to characterize slope behavior during failure and inform stabilization decisions. This study provides crucial data for maintaining and planning the Muketuri-Alem Ketema Road, highlighting slope performance over time and the effectiveness of stabilization techniques.

This study establishes a foundational framework addressing challenges, implications, and potential remedies related to collapsible soils. Serving as a cornerstone for global exploration, it emphasizes the importance of understanding geological, structural, and mechanical characteristics for early identification and proactive mitigation. The study underscores the significance of preventing structural damages in regions prone to collapsible soils, discussing their diverse types and origins, structural composition, and mechanical behavior. A detailed exploration highlights their prevalence in semi-arid and arid regions, emphasizing distinct geological features associated with their occurrence.

The pore structure of aeolian deposits is essential for predicting their mechanical properties and the climatic conditions during their deposition. The discrete element method (DEM) is a practical approach for analysing the formation and evolution mechanisms of aeolian deposits ' pore structure. However, the effect of particle shape and non -contact van der Waals force on deposits ' pore structure with different particle sizes needs further exploration to enhance the efficiency and accuracy of DEM simulations. We developed a VdwForce model for DEM that accounts for the van der Waals force 's long -tail effect, and we conducted loess air -fall numerical tests that matched laboratory simulation tests. DEM simulations and laboratory tests show that the deposits ' porosity increased as the median particle size decreased, whether using spherical or actual shape particles in simulations. When deposits formed by particles with actual shapes have dense packing structures, simulations utilising spherical particles of the same size produce larger porosities. The primary reason of the alteration in the pore structure of the loess air -fall deposits is the shift in the quantity and pattern of particle agglomerates caused by van der Waals attractive force. So, the aggregation process during air -fall was essential for forming overhead pore structures.