Acid contamination has a notable influence on the geotechnical properties of soil and this influence is strongly dependent on contamination concentration (pH) and contamination duration. To fully investigate the effect of acid contamination on the microscopic and strength properties of natural clay, a series of micro- and macrolaboratory tests were performed in this study, and the mechanism of this effect was comprehensively revealed. Microscopic analysis indicates that acid contamination could lead to some mineral transformations in clay, such as illite-smectite transforming into chlorite and illite transforming into kaolinite. Besides, more large pores and a looser structure can be observed in the clay due to the erosional effects of acid contamination, which could effectively weaken the strength properties of natural clay. The experimental results also indicated that, when subjected to acid contamination, the lower contamination pH could lead to a notable decrease in clay's shear strength, while the clay's shear strength increased initially and then decreased as contamination duration increased. In addition, gray correlation analysis results demonstrated that calcite has a significant effect on cohesion, while also indicating a strong correlation between illite and the internal friction angle.

This study delves into the mechanical properties and mechanisms of bentonite-modified cement soil, a reinforced material formed through the physicochemical reactions of cement, soil, and water. Recognizing the material's widespread application in foundation treatment, slope reinforcement, and seepage control, alongside the environmental pressures of cement production, this research explores the potential of bentonite as a partial cement substitute. Through indoor unconfined compressive strength and permeability tests, varied by curing age, bentonite type, and mix ratio, the study assesses the impact of these factors on the material's performance. Microscopic analyses further elucidate the intrinsic mechanisms at play. Key findings include: a non-linear relationship between bentonite content and modified cement soil strength, with sodium-based bentonite enhancing strength more effectively than calcium-based; a significant reduction in permeability coefficient with increased bentonite content, particularly with sodium-based bentonite; and a detailed examination of the material's microstructure, revealing the critical role of cement and bentonite content in pore reduction and strength enhancement. The study underscores the paramount influence of cement content on both strength and permeability, proposing a prioritized framework for optimizing modified cement soil's performance. (c) 2025 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Cement stabilization of soils is a common technique to enhance engineering and mechanical properties of in situ soils in the field of road geotechnics. Usually, moderate quantities of cement are used, around 5-10% of the dry material. However, cement manufacturing is one of the biggest sources of greenhouse gas emissions, specifically carbon dioxide. For this reason, reducing cement content by a few percent in geotechnical structures made with cement-stabilized soils (CSS) has a high environmental interest, particularly in view of the involved volumes of material. This work aims to contribute to a better understanding of the mechanical characteristics of lightly stabilized soils. First, the mechanical behavior of a clayey and a sandy soil treated with 3% cement was studied for several curing times. Next, measured mechanical features were correlated. Finally, these measurements were used to characterize the Mohr-Coulomb failure criterion and compared with a conventional approach. Results point out that mechanical enhancement can be quantified in terms of cohesion. Friction angle seems to be independent of curing time. The proposed approach can be adapted in geotechnical applications based on the Mohr-Coulomb yielding criterion such as stability slopes, foundations, and retaining structures.

The development of ground fissures in the subsidence area induced by shallow-buried extra-thick coal seam mining leads to a decrease in soil water-holding capacity and vegetation withering. The investigation of the spatial distribution characteristics of soil pore structure in mining-induced subsidence areas and the elucidation of the response mechanism between soil physical parameters and soil structure are essential prerequisites for achieving effective ecological environment protection and restoration in mining areas. In this study, three-dimensional visualization reconstruction of soil porosity, pore diameter, roundness rate and pore connectivity at different profile depths in subsidence area caused by ultra-thick coal seam mining was conducted by using the soil CT scanning technology. Additionally, a correlation analysis model was established between physical parameters such as soil moisture content, bulk density, and pore structure parameters. The results indicate that: (1) Compared to the non-subsidence area, the number, size, and proportion of soil pores significantly increase in the tension zone, compression zone, and neutral zone, and the pore network and connectivity are extensively interconnected, and the fissure development in the tension zone is most significant, and the soil pores in the subsidence compression zone are concentrated on one side due to the influence of soil deformation. (2) As the depth of the soil profile increases, the level of soil pore development significantly decreases. The large profile depth (40-100 cm) causes a significant decrease in pore development. (3) There is a significant correlation between soil pore structure parameters and soil physical parameters (P = 0.05), a highly significant correlation between soil pore structure parameters and soil moisture content (P = 0.01), and a highly significant correlation between soil texture and soil moisture content (P = 0.01). This research is of great significance for guiding underground production layout and repairing damaged soil.

Aftershocks frequently induce further damage to slopes that have already been compromised by mainshocks. Most of the current research concentrates on the case-based studies of structural response to the mainshock-aftershock sequences (MAS), however, the influence of the MAS parameter characteristics has not been adequately considered. In this study, the peak characteristic, spectrum characteristic, cumulative characteristic and polarity effect of the MAS were considered, the correlation between 21 MAS parameters and slope response were analyzed, and the response characteristics of soil slope under the MAS action were comprehensively and systematically revealed. The results show that: (1) Aftershocks can induce significant incremental damage to slopes, with the extent of this damage being contingent upon the severity of damage caused by the mainshock; (2) Among the MAS parameters, the Cumulative Absolute Velocity (CAV(ma)) and Peak Ground Velocity (PGV(ma)) are optimal for assessing the response of soil slopes under MAS conditions. Furthermore, the incremental damage caused by aftershocks can be predicted using the displacement increment ratio (delta(D)); (3) The polarity of the MAS has an impact on the displacement of the slope, following the pattern: MAS along-slope direction > mainshock along-slope direction and aftershock reverse-slope direction > aftershock along-slope direction and mainshock reverse-slope direction > MAS reverse-slope direction; (4) The MAS polarity also affects the correlation between the MAS parameters and the slope displacement response, especially for the aftershock displacement. The research results aim to provide a foundation for the selection of evaluation factors and the analysis of soil slopes stability under the MAS action.

The Ili River Valley in Xinjiang, China, is a typical seasonal frozen area where loess landslide disasters have become increasingly common during the freeze-thaw periods in recent years. This study analyzed the macroscopic mechanical strength and microstructure changes of the Ili loess under different freeze-thaw cycles (FTCs) through the post-freeze-thaw triaxial compression test on the unsaturated soil in laboratory. Apart from the scanning electron microscopy (SEM), and the nuclear magnetic resonance (NMR), the macro-micro correlation analysis and the cluster-principal component analysis were applied for the theoretical discussion. The results indicated that the cohesive force of the loess exhibits an initial decreases, followed by the increases, and eventually keep stable after various FTCs, while the internal friction angle showed the opposite developing trend before the final constant. Similar to the strong correlation between the cohesive force and the particle abundance, the internal friction angle is also closely related to the abundance and orientation fractal dimension of the loess particles. However, the principal component analysis results showed that cohesive force strongly correlates with the average maximum pore size and the pore size fractal dimension, for which the internal friction angle most strongly affected by the average maximum particle size. The possible reason is that the extracted principal components represent a class of microscopic parameters with the same or similar change trend, although there may be a certain offset between them. The mechanical deterioration of loess is attributed to the repeated frost heaving force and the migration potential caused by FTCs. The alterations of the microstructure accelerated the deterioration of the macroscopic mechanical properties of the loess, which further widens the understanding of the mechanism behind the deterioration of loess mechanical strength in the Ili River Valley under FTCs, and contributes to the prevention and management of the local landslide disasters.

Sargassum horneri which seasonally enters East Asian waters frequently leads to negative economic consequences despite its ecological importance. It damages vessel engines and fishing gear and releases hydrogen sulfide and ammonia as it rots. Traditionally, seaweed drifts have been used as fertilizers in certain coastal areas in Korea, but there have been no scientific reports regarding this kind of application of seaweeds. Hence, this study attempted to use Sargassum biomass as a soil amendment by monitoring soil properties and microbiome changes and soybean growth in Sargassum-added soil. Our results suggested that the addition of S. horneri biomass to soil improved soil physicochemical properties such as cation exchange capacity (CEC) levels that represents soil's capacity to retain cations leading to more soil fertility. As (max. value 24.97 mg kg(-1)) and Cd (max. value 0.58 mg kg(-1)) concentration increases were notable in the soil, but all the metal levels were well below the Korean soil quality standards for agricultural uses except for As (25 mg kg(-1) limit) which is just a little lower than the limit. Diversity index results indicated that fungal and bacterial diversities were affected by the amount of Sargassum added. Our study demonstrated that seasonal drifts of S. horneri could be used as an excellent soil amendment. Moreover, Glycine max (L.) Merr. cultivation experiments suggested that 4% of S. horneri was the optimal amount to enhance soybean growth in agricultural practice.

Nickel-iron slag, a byproduct of industrial processes in China with an annual production exceeding 400,000 tons, is considered an industrial waste material. This study focuses on the rational utilization of nickel-iron slag by investigating its mechanical properties and road performance as a roadbed fill material. Initially, a detailed analysis of the grading curve of pure nickel-iron slag was conducted, leading to the proposal of various modification schemes for nickel-iron slag. Subsequently, static triaxial tests were performed on nickel-iron slag-clay mixtures to explore the impact of different factors on the stress-strain curve of nickel- iron slag-modified soil. Utilizing these discoveries, a formula for the molar Coulomb shear strength of nickel-iron slag-modified soil was derived. In addition, a numerical simulation study of a nickel-iron slagreinforced embankment was conducted, integrating field tests. This aimed to investigate the variations in the compression layer sedimentation-thickness ratio and settlement factor of nickel-iron slag-modified soil reinforced embankment under different filling heights and slope rates. The results informed the development of a prediction model for the settlement ratio of nickel-iron slag-modified soil-reinforced embankment. Key findings indicate that pure nickel-iron slag exhibits poorly graded gravel sand characteristics, and optimal gradation is achieved when clay doping ranges from 30% to 40%. As the clay content increases, the stress- strain curve of nickel-iron slag-clay transitions from strain-hardening to strain-softening. Furthermore, the stress-strain curve of nickel-iron slag-cement-clay exhibits strain-softening, and the shear strength fitting formula demonstrates high computational accuracy with a small error range. Numerical simulations reveal that the sink-thickness ratio and settlement factor are minimally affected by the slope rate. The sink-thickness ratio increases with the elevation of filling height, while the settlement factor fluctuates within a small range. The proposed sink-thickness ratio prediction model exhibits high accuracy and strong generalization capabilities. This comprehensive study provides valuable insights into the efficient utilization of nickel-iron slag in construction and road engineering.

In earthquake-resistant design, amplitude and frequency content of ground motions (GMs) have been considered using spectral matching techniques; however, duration effects remain insufficiently explored in designing buildings in liquefiable soils. This study investigates the influence of ground-motion duration on seismic response of shallow-founded buildings under strong earthquakes. Buildings in liquefiable soils are analyzed using nonlinear dynamic analysis with coupled u-p formulations. The numerical code and calibrated constitutive parameters of Toyoura sand are validated through dynamic centrifuge testing. Two ground-motion suites, including 30 pairs of long and short-duration events, are scaled to the target PGA of 0.3 g, and then selected to be spectrally equivalent to isolate duration measures from the others. Comparative results show that longer duration events result in greater settlements and tilt compared to shorter events. Therefore, this study emphasizes the importance of considering duration measures in assessing seismic responses of buildings. Furthermore, correlation between settlements and peak transient tilt, and intensity measures (IMs) of GMs are comprehensively analyzed. It is found that employing compound IMs can lead to notable improvements in predictive accuracy for settlement and peak transient tilt compared to single common IMs. The compound IMs, namely CAV2/3 x Ds5-951/3 and SMV x Ds5-95 3, are newly proposed for use in order to achieve best correlation with the shear-induced settlements and peak transient tilt, respectively.

Coal mining in arid western regions is damaging the fragile ecology, causing problems such as surface damage, vegetation destruction, and soil erosion. These issues are obstacles to the development of green coal, as mining activities can disrupt the distribution of surface vegetation, leading to its spread outside the mining area and affecting surrounding areas. Based on Landsat data, the binary pixel model was used to calculate the vegetation coverage (FVC) in mining area from 2005 to 2021. Through vegetation coverage classification and regression trend analysis, the temporal and spatial changes and evolution trends of vegetation disturbance caused by coal mining and climate were analyzed. Correlation analysis revealed the range of ecological disturbance caused by coal mining at the coal mine scale and mining area scale. The results show that the vegetation coverage of the mining area showed a decreasing trend from 2005 to 2021. Winter and spring precipitation was the primary factor affecting vegetation growth in the area, while coal mining had indirect and secondary effects on vegetation. Human activities played a significant role in improving vegetation, and between 2015 and 2018, the area of vegetation improvement increased by 133.41% compared to that of 2009-2014. Compared to the reference area, the impact range of vegetation disturbance in the mining area is 2.5-5 km, while the impact range of vegetation disturbance in the coal mine is less than 500 m. Therefore, this study provides a theoretical basis for studying the impact of mining activities on vegetation and boundary identification.