The soil fabric varies significantly depending on the deposition process that forms the grain skeleton. Each deposition method produces a specific type of soil fabric, which can be linked to a particular soil density. When represented as relative density, determined using limit densities from standard index tests, a wide range of relative densities can be observed for different sands produced by the same deposition method. The influence of this variation in relative density, resulting from a single deposition method, on the development of the excess pore water pressure (PWP) should be further investigated. A fast testing of the excess PWP accumulation in sandy soils during undrained cyclic shearing can be easily performed using the newly developed PWP Tester. In the PWP Tester, specimens are prepared through sedimentation in water, which yields a comparable fabric in different sands but significantly different relative densities. Despite these relative density differences, the rate of the excess PWP evolution during undrained shearing is remarkably similar among different sands. This indicates that relative density should not be regarded as a primary factor influencing the development of the excess PWP and that the soil fabric plays equal or even a greater role.

In-depth research on the mechanical properties and constitutive models of gas hydrate-bearing sediments (GHBSs) is fundamental for achieving efficient hydrate exploration and geological disaster prevention. In the current study, a bounding surface model for GHBSs is developed based on the principle of thermodynamics. By choosing an appropriate dissipation function and free energy function, a yield surface function containing three shape parameters can be obtained. Considering the filling and bonding effects of hydrates, and introducing the hydrate strength evolution parameter, a thermodynamics-based bounding surface model for GHBSs is established using a non-associated flow rule. Then, the explicit substeping scheme with error control is implemented to develop a UMAT subroutine for the proposed model and integrated into the ABAQUS. Compared with the drained monotonic triaxial shear data indicates that the proposed model can adequately capture the shear behaviors of sandy, silty sandy, and clay-silty GHBSs under different stress levels and saturations. In addition, the model demonstrates good applicability and feasibility in undrained cyclic triaxial shear tests and boundary value problem analysis.

In eutrophic shallow lakes, cyanobacterial blooms will occur frequently and then settle into sediment, leading the formation of fluid sediment. Several factors including temperature can influence surface sediment properties. In this study, the influence of temperatures on surface sediment properties was determined in microcosm experiments through monitoring sediment physicochemical and rheological properties. During one-month incubation, it was found that surface sediment density and water content varied exponentially with increase in temperatures from 10 to 35 degrees C. The results of particle size distribution indicated that cyanobacterial blooms biomass (CBB) degradation in sediment led to sediment flocculation and agglomeration. In the meantime, there were high ratios polysaccharide/protein in extracellular polymeric substances (EPSs), which enhanced the sediment particle agglomeration. Further, the yield stress in rheological test for sediment with ( R2 = 0.97) and without ( R2 = 0.85) CBB presented an exponential decay with increase in temperatures. And a threshold value at 20 degrees C for sediment critical shear stress ( tcr ) indicated that sediment could be resuspended easier when temperature was more than 20 degrees C. Altogether, this study showed that the increase in temperatures with a threshold at 20 degrees C, can cause sediment particle flocculation, resulting in a loose and fragile structure. And the results would be helpful to sediment management considering environmental effects of sediment suspension for eutrophication shallow lakes. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential of hydrate reservoirs under exploration conditions. However, the characteristics and simulation of this shear strength under varying dissociation conditions have not been thoroughly investigated. To this end, a series of triaxial compression tests were first carried out on sediments with varying initial hydrate saturations along dissociation pathways. Combining measured data with microscale analysis, the underlying mechanism for the evolution of shear strength in hydrate-bearing sediment was studied under varying partial dissociation pathways. Moreover, a shear strength model for hydrate-bearing sediment was proposed, taking into account the hydrate saturation and the unhydrated water content. Apart from the parameters derived from the hydrate characteristic curve, only one additional model parameter is required. The proposed model was validated using measured data on hydrate sediments. The results indicate that the proposed model can effectively capture the shear strength behavior of hydrate-bearing sediment under varying dissociation paths. Finally, a sensitivity analysis of the model parameters was conducted to characterize the proposed model. (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 evaluated the stabilization of dam sediment using a blended binder of eucalyptus wood ash (EWA) and cement for cost-effective and environmentally safe pavement material development. The sediment is classified as a sandy lean clay. EWA, a pozzolanic byproduct, was used as a partial cement replacement to enhance the material's geotechnical properties and reduce environmental impact. The optimized mixture showed a 12-fold increase in unconfined compressive strength (1.4 MPa) and a California bearing ratio of 70%, meeting Thailand Department of Highways' specifications for subbase and base layers. The microstructural analysis confirmed the formation of calcium silicate hydrates, improving durability and reducing weight loss by 30% under wetting-drying cycles. Leachate tests showed that heavy metal concentrations remained within regulatory limits. EWA also reduced costs by 2.6 times compared to conventional stabilization methods, highlighting its potential for pavement applications.

Studying the rheological properties of deep-sea shallow sediments can provide basic mechanical characteristics for designing deep-sea mining vehicles driving on the soft seabed, providing anchoring stability of semi-submersible mining platforms, and assessing submarine landslide hazards. Shallow sediment column samples from the Western Pacific mining area were obtained, and their rheological properties were studied. A series of rheological tests was conducted under different conditions using an RST rheometer. In addition, conventional physical property, mineral composition, and microstructure analyses were conducted. The results showed that shallow sediments have a high liquid limit and plasticity, with flocculent and honeycomb-like flaky structures as the main microstructure types. The rheological properties exhibited typical non-Newtonian fluid characteristics with yield stress and shear-thinning phenomena during the shearing process. In contrast to previous studies on deep-sea soft soil sediments, a remarkable long-range shear-softening stage, called the thixotropic fluid stage, was discovered in the overall rheological curve. A four-stage model is proposed for the transition mechanism of deep-sea shallow sediments from the solid to liquid-solid, solid-liquid transition, thixotropic fluid, and stable fluid stages. The mechanism of the newly added thixotropic fluid stage was quantitatively analyzed using a modified Cross rheological model, and this stage was inferred from the perspective of mineralogy and microstructure. The results of this study can be useful for improving the operational safety and work efficiency of submarine operation equipment for deep-sea mining in the Western Pacific Ocean. (c) 2025 Japanese Geotechnical Society. 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/).

The growth and evolution of sinkholes are a considerable proportion of the damage related to subsidence disaster in alluvial areas after ground water extraction for irrigation. In this research it was tried to study the evolution of the sinkholes from the birth point to the stabilization or final step. In the Eqlid-Abarkooh alluvial fan was selected an area about 300 km2 with giant sinkholes where consist; the city of Abarkooh, arable irrigated lands and desert rangelands. The major aspect on the study area was southwest to northeast where it ended to Abarkooh playa. For investigating the formation and evolution of these sinkholes in the study area, field observation for 2 years were done. Soil samples were taken from surface soils (0-25 cm) near and far of the sinkholes. Moreover, 4 soil samples were obtained from the deepest sinkhole as control sample in the study area. Chemical, physical and mechanical soil analyses were performed. Finally, the Ground Penetrating Radar (GPR) method were done for detection subsurface holes to depth of 4 m around the sinkholes. The chemical soil properties results include Electro Conductivity (EC) and the ratio of Ca2+/Mg2+ in lime which was important factors to formation of sinkholes changed from 2.05 to 19.3 dS/m, 0.15 to 6 respectively. The mechanical soil parameters such as Coefficient of Linear Extensibility (COLE) and Plasticity Index (PI) changed from 0.05 to 1.67, 0.99% to 15% respectively. According to sinkhole development, the results obtained that there was a relationship between diameter of sinkhole obtained from 0.6 to 15 m and groundwater extraction quantity changed from 0.18 to 18.14 m3/ha over 25 years. The groundwater level dropped 15 m and sinkhole volume variation obtained 0.014 to 2650 m3 over 25 years. Field discovery and google earth images showed that sinkholes were developed in 3 phases as (1) growth phase (2) mature and (3) steady phases up to about 25 years. The GPR results found some land breaks and a hole underground in the activation and growth phase of sinkhole evolution. Finally, according to some soil parameters and GPR results, the sinkhole hazard map was created in the study area.

The global impacts of agricultural land conversion on soil erosion and pollution, particularly in tobacco cultivation areas, are well-recognized as significant contributors to soil degradation. These areas are identified as hotspots for environmental concerns due to practices that lead to increased erosion and pollution. From this perspective, this case of study explores fine sediment samples from two areas with tobacco cultivation under different tillage systems and seasonal variations, transport into a headwater, and evaluates, on a local scale: (1) the impact of tillage systems on the geochemical signature of sediments; (2) if whether crop seasonality affects these sediment geochemical signatures. The Conventional Ridge Tillage (CRT) system involves extensive soil exposure and machinery for soil management, while the Mulch Ridge Tillage (MRT) system prioritizes soil conservation and relies on herbicides for weed control. The analytical methodology used to assess the sample element characteristics was Energy Dispersive X-ray Fluorescence (EDXRF). It was applied on the twenty fine sediments (ten of harvest and ten of inter-harvest season of tobacco) to quantitatively assess their inorganic composition. Additionally, Pearson correlation analysis, Hierarchical Cluster Analysis (HCA), and Principal Component Analysis (PCA) were applied on the EDXRF data to highlight the similarities and, thus, providing information to assess the complex data clustering patterns. As a result, the sediment compositions from the two studied soil systems are not similar. The PCA showed that the CRT sediments are characterized by the P, S, K, Ca, and Mn content, presenting a geochemical signature related to manure and fertilizer compared to the MRT, which is correlated with Al, Ti, Fe, Cu, and Zn contents, exhibiting a geochemical signature characterized by the natural soil composition. Therefore, the sediment geochemical signatures might be affected by two phases in the study area: a) tillage system characteristics and b) seasonal soil erosion. These findings underscore the importance of managing soil nutrients to mitigate soil pollution and nutrient exportation to aquatic systems. Moreover, the results emphasize the recommendations for sustainable agricultural practices in tobacco-growing areas to protect environmental quality.

Human impact in the form of reservoir construction and river regulation downstream of reservoirs, is causing irreversible alterations to hillslope and river channel connectivity in river catchments. This disruption in the dynamic equilibrium of the river is attributed to sediment accumulation upstream of the reservoir's dam, limited sediment outflow from the reservoir, and increased downcutting downstream of the dam. Consequently, these alterations necessitate further human interference in natural environmental processes through the construction of various river engineering structures designed to reduce the intensity of downcutting. The purpose of the present study was to assess the impact of a small mountain reservoir and additional river regulation structures on the Wapienica River in southern Poland, focusing on the structural and functional connectivity of the river channel in terms of sediment transfer. This assessment was based on erosion and connectivity modeling, as well as field mapping. A high-resolution digital elevation model (HRDEM) was examined in the study along with survey data on suspended sediment accumulation sites along the river. The study utilized open-source tools, including SedInConnect for connectivity index (IC) calculation, and the Soil and Water Assessment Tool (SWAT) for ArcGIS software. It was found that the Wapienica reservoir permanently retains the floating material, making the likelihood of this material flowing out of the reservoir minimal. Within the reverse delta of the reservoir, the entire load of bottom material (sand) is also retained. Thicker bottom material (gravel, boulders) is deposited in the riverbed within the delta, leading to the shallowing of the bed upstream of the delta. These processes disrupt longitudinal connectivity. Six connectivity zones have been identified within the catchment. The first four are situated in the southern part of the catchment: strong connectivity, reduction, concrete channel, and damage area. The remaining two, situated in the northern part are: artificial channel and drainage channels. Each of the six zones is characterized by different sediments and river processes. It was demonstrated that a more detailed and more probably connectivity pattern for hillslopes and river channels may be obtained through the use of several tools and parameters at the same time (i.e., fieldwork, SWAT, IC).

This paper aims to develop geopolymer concrete (GPC) with flash-calcined soils cured under ambient conditions. Flash calcination is a heat thermal technique used to eliminate pollutants and organic content in excavated soils and allow them to be used in cementitious formulations. To develop GPC, the materials used in the development of the GP precursor binder should be rich in silicon (Si) and Aluminum (Al) that can react with alkaline silicates to yield Si-O-Al bonds that would form cementitious materials. The GP precursor binder is composed of Metakaolin (MK), flash-calcined soils, and granulated blast furnace slag (GBFS). The thermally treated soils are flash-calcined dredged sediments (FCS) and flash-calcined excavated clays (FCC) while potassium silicate is used as the alkaline reagent. This study aims to use the materials above to develop GPC cured under ambient conditions with high strength, good durability, and microstructure properties. Seven formulations are done to evaluate the effect of replacing MK with either FCS or FCC and GBFS on the mechanical compressive strength, water absorption, and freeze-thaw test. The findings reveal that using only metakaolin (MK0) in the formulation yielded the highest compressive strength. These results align with the porosity test outcomes, which show correlations between micropore and macropore percentages. Analysis of the durability freeze-thaw test suggests that as the proportion of macropores increases, formulations incorporating FCS and FCC exhibit improved resistance to extreme temperatures. Conversely, an increase in GBFS content leads to a finer microstructure and reduced resistance. Water absorption testing indicates that formulations with FCS and FCC display favorable sorptivity coefficients compared to MK0, with increased GBFS content enhancing durability. SEM/EDS and calorimetry tests were conducted to investigate the impact of substituting FCS and FCC for MK within the geopolymer matrix.