Bulletin of Engineering Geology and the Environment最新文献

The portable, non-destructive Leeb hardness tester is widely used to predict rock material properties. However, the lack of standardized procedures for its application in rock engineering can lead to inaccurate design parameters and increased risks. Therefore, this paper systematically explores effective methods for conducting the Leeb hardness test for rocks. 90 samples of six rock types from different regions were collected, totaling over 1800 test results. Furthermore, this study analyzes how factors such as the number of tests, testing practices, moisture conditions, surface roughness, and sample size influence Leeb hardness testing. Results show that each sample should be tested at least 20 times, with test points evenly distributed in the center area at least 10 mm from the edges of the cylindrical sample’s top and bottom surfaces. The Leeb hardness values in different moisture states relate to water absorption rates and elastic modulus. Thus, rocks with high absorption rates should be measured after drying. A 3D optical profilometer measured surface roughness, and the resulting Joint Roughness Coefficient (JRC) indicated that field polishing with a grinding machine meets test requirements. Considering size effects, cylindrical samples should have a minimum height of 25 mm and an optimal height-to-diameter ratio exceeding 2. A modified empirical formula is proposed. Rocks are catehorized into four hardness classes, and Leeb hardness is suggested as a supplementary parameter for comprehensive rock mass classification and engineering design.

Transversely isotropic unsaturated loess is widely distributed in the Loess Plateau in northwestern China. Its water-holding characteristics directly affect the stability and safety of engineering structures, such as foundations and slopes. During deposition, loess depositional planes exhibit varying inclination angles relative to the horizontal plane, which can influence the distribution and migration patterns of soil moisture. To investigate how different depositional angles influence the water-holding characteristics of transversely isotropic unsaturated loess, this study used a pressure plate apparatus to perform six sets of soil-water characteristic curve (SWCC) tests on undisturbed and remolded loess. SWCCs were obtained for both types of loess. The results indicate that, under identical suction conditions, the volumetric water content of the soil samples decreased as the depositional angle increases. The SWCC of undisturbed loess exhibits greater dispersion across angles than that of remolded loess and has superior overall water-holding capacity. After compaction treatment, the water-holding capacity of remolded loess decreases overall. Fitting analysis of the experimental data using the VG model revealed that the depositional angle influences the air entry value and dehydration rate of the loess. A conversion relationship was established between the depositional plane coordinate system and the original coordinate system, and a three dimensional rotation matrix was derived. Through coordinate system transformation, the depositional plane parameter was incorporated into the VG model, yielding a modified VG model that considers the depositional angle. Preliminary validation demonstrated satisfactory results, providing a reference for engineering designs involving loess foundations and slopes.

In cold regions, slope pemmafrost distributes widely. Steep slopes and solar exposure differences cause non-uniform temperature fields, forming ice lenses with varying inclinations and thicknesses that enhance permafrost anisotropy and affect mechanica properties. This study conducts triaxial tests on frozen silty clay with ice lenses under different temperatures, inclinations, thicknesses, and confining pressures, obtaining deviatoric stress-strain curves. The results indicate that the morphology of these ice lenses does not significantly alter the failure pattern of frozen soil. The inclination of ice lenses has a noticeable weakening influence on frozen soil strength. Under identical soil temperatures, an increase in the inclination angle of the ice lens correlates to a reduction in the frozen soil’s compressive strength. Furthermore, the thickness of ice lenses contributes positively to enhancing the strength characteristics of frozen soil; specifically, specimens with thicker ice lenses exhibit higher compressive strengths. As confining pressure increases, so too does the influence exerted by thick ice lenses on compressive strength also becomes increasingly significant. As we observe changes in inclination angles among these ice lenses, both cohesion and internal friction angles within frozen soil are found to diminish. Notably, while reductions in internal friction angles are relatively modest and display linear trends, cohesion experiences substantial declines—particularly pronounced within frozen soil characterized by thicker ice lenses.An empirical formula for the compressive strength of frozen soil considering the temperature of frozen soil and the inclination of ice lenses is given, comprehensively revealing the impact of ice lenses on frozen soil’s mechanical characteristics.

Machine learning has become a pivotal tool for geohazard susceptibility assessment; however, its performance is often constrained by the inherent scarcity and uncertain reliability of geohazard samples, a critical challenge in geoscience that can lead to model inaccuracies. To address this issue, this study introduces a Sample Enhancement Algorithm (SEA) to systematically improve training data quality. Using Guangzhou City as a case study, the SEA framework constructs a high-quality training dataset by quantifying sample reliability through a weighted environmental similarity approach based on prototype theory. The XGBoost model, trained on this enhanced dataset, demonstrates significant performance gains. For instance, in collapse scenarios, applying SEA with reliability thresholds of R_P ≥ 0.85 and R_N ≥ 0.5 improved model accuracy from 0.714 to 0.954 and AUC from 0.897 to 0.99. The study also reveals a critical trade-off, where overly strict reliability thresholds can reduce sample size and adversely affect model performance. Furthermore, validation against historical data highlights the impact of spatiotemporal heterogeneity on model generalization. Overall, these findings offer a quantitative, practical foundation for regional hazard risk management by underscoring the importance of balancing sample reliability with quantity and diversity to develop timely and generalizable models.

In the initial investigations on hazard assessment at regional (1:25,000) and semi-detailed (1:5. 000) scale of one of the landslides occurred in the sector of Cortinas, Colombia (2021), has been demonstrating the novel hypothesis of the influence of the variation of the conditioning factors over time, a process called Accumulated Geotechnical Deterioration (AGD) in the occurrence of a geotechnical instability event, which does not properly depend on the critical thresholds of the triggering factors as commonly considered. This study focuses on analyzing the influence of the AGD on a detailed scale (1:2,000). Four stability analyses were performed to obtain the factors of safety by the limit equilibrium method using soil strength and permeability parameters obtained from field tests, conducted on four different dates (years 2017, 2021, 2023, 2024) over a period of 7 years. The results of the stability analyses show that the safety factors of 2017 were higher than those of 2021 (Landslide) and that for the years 2023 and 2024 these values increased progressively, consistent with the results of the resistance parameters obtained in the area for each date. According to the analyses performed, can be concluded that the soil as a conditioning factor undergoes cycles of recovery and deterioration due to the effects of the triggers (AGD) until it goes back to a failure condition; therefore, the AGD could be determinant in the prediction of future instability events in a study area, as long as proper monitoring of the resistance parameters is carried out.

Earth dams with embedded structures such as culverts and pipelines are essential components of modern hydraulic systems, facilitating water diversion, drainage, flood discharge, and cross-dam transport. However, these internal inclusions create material discontinuities and weak interfaces, making the dam susceptible to seepage-induced damage. This study investigates the mechanisms of contact leakage and the effectiveness of polymer grouting repair through a comprehensive framework integrating theory, full-scale physical testing, and numerical modeling. A full-scale embankment model with dual embedded pipelines was constructed to replicate seepage damage under controlled hydraulic loading. Advanced multi-sensor monitoring alongside geophysical techniques accurately captured the initiation and development of seepage and enabled precise localization of defects. Two polymer grout types—expandable and permeable—were applied for targeted remediation. Results show that by precisely controlling the rates of gas generation and curing during the polymerization process, porous foam or network gel microstructures are formed. These microstructures not only effectively densify and block seepage pathways but also significantly improve interfacial adhesion, reduce internal friction, and enhance the overall load-bearing capacity and deformation compatibility of the interface, thus realizing a synergistic sealing and flow-guiding effect. A validated 3D dam-pipeline coupled numerical model through test results was developed to simulate seepage-stress interaction and assess dam stability before and after repair using the strength reduction method. The findings highlight the critical role of interface conditions in seepage damage and demonstrate the engineering feasibility of polymer grouting repair technology for embedded pipeline dams.

Loess is generally unsuitable as a landfill cover material because of its loose structure, high porosity, and poor cohesion. This study investigated whether a waste water-based drilling geopolymer (WWDG) can reduce loess gas permeability (GP) by hardening the soil. Triaxial GP tests were performed to quantify the effects of WWDG content (ω_a), confining pressure (p), water content (ω), and dry density (ρ_d) on GP. The findings inform strategies for waste reutilization and loess improvement. Microstructural and compositional changes in WWDG-improved loess were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The study further clarified the curing mechanism of the WWDG-improveed loess. Results showed that the distribution of GP coefficients narrowed under the combined influence of the tested factors. ω_a had the greatest impact on GP. Increasing ω_a, p, ω, and ρ_d decreased the GP coefficients by 93.15%, 90.68%, 83.50%, and 85.48%, respectively. As ω_a increased, clay mineral content in the loess first increased and then decreased, whereas the feldspar content followed the opposite trend. WWDG filled loess pores, altered pore structure, and reduced porosity, thereby producing a more stable soil framework. Overall, WWDG shows potential for improving the engineering performance of the loess.

Shale, characterized by its laminated and fissile nature, exhibits significant anisotropy due to its thin, easily split bedding planes. The mechanical properties of shale vary with bedding plane orientations, posing challenges in modeling its complex structure. Previous research often oversimplifies bedding planes by treating them as continuous, straight, and equidistant, neglecting the anisotropic effects of varied bedding plane orientations. This study addresses these limitations by developing a comprehensive methodology for establishing and calibrating a realistic hybrid bedding-plane DEM model for shale specimens, enabling more accurate prediction of mechanical behavior. The shale models incorporate accurate bedding plane representations through image processing. The bedding plane lengths follow a log-normal distribution, with the mean length (LN) of 1.22 cm and the standard deviation (LN) of 1.05 cm. A systematic calibration procedure was developed for the shale hybrid bedding-plane DEM model at the laboratory scale. The results demonstrate that the calibrated UDEC model not only replicates stress-strain behaviors but also accurately captures failure modes across bedding plane orientations. The calibrated micro-properties for the trigon and bedding plane contacts align closely with laboratory observations, highlighting the effectiveness of the hybrid bedding-plane DEM model. This study bridges the gap between shale’s complex structure and geomechanical simulations, providing a robust framework for accurate anisotropic modeling of shale specimens.

As one of the most representative hydropower project areas in China and globally, the Three Gorges Reservoir Area (TGRA) has attracted significant attention due to its complex geological setting and frequent geological hazards. This study provides a systematic review of recent advances in landslide assessment within the TGRA, outlining the technological evolution from traditional limit equilibrium methods, numerical simulations, and physical model tests to the integration of big data and machine learning approaches. The theoretical foundations, application effectiveness, and limitations of each method are analyzed in detail. The findings indicate that the deep integration of machine learning and remote sensing technologies has significantly improved the spatial and temporal resolution of landslide prediction. Frontier approaches, such as ensemble models (e.g., Stacking, XGBoost) and physics-informed neural networks (PINN), have demonstrated considerable potential. However, challenges persist, including limited data quality, insufficient model generalization, lag in dynamic assessment, and inadequate quantification of climate change impacts. In response, this paper proposes a four-tier theoretical framework encompassing stability–susceptibility–hazard–risk, which elucidates the technical linkages and integration pathways for multi-scale assessments. Future research directions are proposed with a focus on dynamic monitoring, mechanism-informed modeling, and climate adaptation. These findings aim to provide a scientific basis for landslide disaster mitigation and risk management in the TGRA and offer theoretical support for regional geological hazard control and sustainable development.

Earthen plaster is a commonly used traditional technique in geotechnical construction and has been widely applied in the grotto murals of northwestern China, exhibiting significant historical and cultural value. Due to factors such as rain and irrigation, water often infiltrates into the earthen plaster layer through the substrate or foundation. This water often carries salts, leading to the disintegration of the earthen plaster. However, the disintegration characteristics of such earthen plaster under water-salt interaction remain unclear, and there are few studies on the effectiveness of currently popular natural hydraulic lime (NHL) restoration materials in improving disintegration, which is detrimental to the subsequent conservation of the earthen plaster. To investigate the disintegration characteristics of earthen plaster, 9 plaster samples were prepared, and surface contact angle tests, disintegration tests, and microscopic structure tests were conducted. The results showed that when only Dengban clay was used as a binder, the plaster completely disintegrated. Adding fibers to the plaster could resist disintegration to some extent. Adding NHL improved the water-repellent properties of the earthen plaster’s surface, and 10% NHL prevented the plaster layer from disintegrating. Low concentrations of salt solution had no significant effect on the disintegration process in the short term, but long-term exposure to salt solutions caused new salts to form through reactions with the hydrates of NHL.