Bulletin of Engineering Geology and the Environment最新文献

Identifying cracks in rock blasting provides an accurate representation of the crack network that occurs during the blasting process. It serves as a crucial tool for the precise evaluation of the dynamic response characteristics of rocks. However, most crack characterizations rely on manual measurements, which are often inaccurate, prone to significant errors, and are both time-consuming and costly. Therefore, this study compiled a database of 1,000 images of rock blasting fractures. The images were divided into foreground and background images by Faster RCNN. Five parameters were selected as the input variables, with the optimal image threshold set as the prediction target. A deep extreme learning machine (DELM) was optimized using swarm intelligence algorithms to develop eight hybrid models. The performances of these prediction models were comprehensively evaluated using four metrics. The results indicate that the proposed DELM-based hybrid model can consistently provide accurate predictions of the optimal image threshold. The DELM model using the zebra optimization algorithm performed best, with a root mean square error (RMSE) of 0.027 and a mean absolute percentage error (MAPE) of 4.58%. Finally, the proposed calculation method could quickly and accurately extract crack characteristics, including the crack network area, crack length, crack twist angle, and maximum crack width. The research results of this study could provide an effective way to identify the crack network characteristics.

This study aims to assess the sensitivity of landslide susceptibility mapping (LSM) to various sampling strategies used for non-landslide samples. The study area is Tianshui city, Gansu province, China. Three types of landslide samples, combined with four machine learning models, resulted in a total of 12 scenarios. The receiver operating characteristic curve (ROC), landslide susceptibility index and the mapping distribution characteristics were calculated to access the influences of different sampling strategies and models. The results indicate that the low susceptibility areas sampling strategy yields the highest accuracy for the landslide susceptibility prediction model, followed by the stratified sampling from engineering geological petrofabric (EGP) strategy, and lastly, the random sampling strategy. Analyzing from the perspective of factor importance and the distribution law of landslide susceptibility index under each model, the models employing the stratified sampling from EGP strategy demonstrate greater robustness. In contrast, the models using the random sampling strategy exhibit lower precision and more randomness. In general, the coupled model exhibits strong performance, the frequency ratio coupled adaptive boosting model (FR-AB) demonstrates high sensitivity, while the other models are characterized by their generalizability and robustness. The results reveal the effects of non-landslide sampling strategies and different coupled models on the prediction performance of landslide susceptibility mapping, which provides a reference for subsequent researchers to obtain more reasonable landslide susceptibility mapping.

This paper presents an experimental study on how particle sphericity affects the shear behaviors of uniformly graded sand. Using the Wadell 3D sphericity index S, the study examines natural calcareous sand and quartz sand grains. Five typical forms with varying sphericities were selected: S0 represents a perfect sphere (S = 1.000), while S1, S2, S3, and S4 denote irregular forms derived from natural calcareous sand and quartz sand, with S values of 0.954, 0.914, 0.888, and 0.848, respectively. Artificial sand particles with specific sphericities were then fabricated using a 3D printer. A series of consolidated-drained triaxial compression tests were conducted on these artificial sand particles at four different confining pressures ranging from 20 kPa to 100 kPa. The results show that the shear strength of sand increases with decreasing sphericity, as evidenced by an increase in both peak-state and critical-state friction angles. This suggests that irregular shapes enhance the shear strength of sand. Regarding the sand dilatancy under shear, the relationship with sphericity is complicated. As sphericity decreases, the maximum dilation angle increases under a low confining pressure, whereas it initially decreases and then increases under high confining pressures. Predictive models, which are capable of estimating peak-state friction angle, critical-state friction angle, and maximum dilation angle, were developed for a given sphericity and confining pressure. Verification of Bolton’s stress-dilatancy equation revealed a constant dilatancy coefficient for the artificial sand particles with different sphericities, suggesting that the contribution of dilatancy to the excess strength of sand remains independent of particle shape.

Soil-rock interface landslides are common geological hazards in mountainous regions. While conventional cement-based micropiles are widely used for slope stabilization, their long curing time limits their application in emergency treatments. This study introduces polymer micropiles as a rapid-response alternative, leveraging the quick-setting and high tensile strength properties of polymer grouts. Field-scale tests and numerical simulations were performed to investigate the mechanical response and settlement deformation characteristics of the bedding slopes reinforced with polymer micropiles under loading. Results showed that polymer micropiles significantly improved slope bearing capacity, reduced crest settlement, and decreased surface displacement. Specifically, the bearing capacity of slopes reinforced with single and double rows of polymer micropiles increased by 111% and 211%, respectively, compared to the unreinforced slope. Settlement at the slope crest decreased by 76.9% and 90.4%, while lateral displacement at the slope toe was reduced by 77.8% and 92.8%. The final slope morphologies showed significant differences, with pronounced extrusion and soil detachment observed in the untreated slope, contrasted by only minor surface cracks in the polymer micropile reinforced slope. The simulations revealed that the micropiles fractured at the sliding plane when reaching the ultimate bearing capacity, indicating the compatibility of polymer micropile with the slope soils and the reinforcing effect of the micropiles. These findings demonstrate the feasibility and effectiveness of polymer micropiles for emergency landslide stabilization, offering a critical window for disaster response and permanent slope stabilization efforts.

Numerous dangerous rock blocks are located on rock slopes, potentially threatening the construction and safety operation of the adjacent engineering facilities. The dangerous rock block identification has been realized for decades in rock mechanics and engineering. However, studies on the automated identification of in-situ dangerous rock blocks (ISDRBs) are limited. In this study, a novel framework is proposed for automated extraction of ISDRBs based on a new semi-deterministic block theory considering discontinuity geometric characteristics. It involves four main steps: (1) establishment of the slope point cloud model using an unmanned aerial vehicle multi-angle photography method; (2) automated identification and information extraction of discontinuities based on various algorithms; (3) identification and geometrical characterization of in-situ rock blocks (ISRBs) based on the improved block candidates searching algorithm and polyhedral modeling; (4) stability analysis of ISRBs to extract ISDRBs based on the semi-deterministic block theory. In this framework, the actual positions, geometric characteristics, and safety factors of ISDRBs can be well-reflected, providing a quantitative reference for rockfall disaster prevention and mitigation design. The framework is applied to the stability analysis of the steep rocky slope on the left bank of the Nujiang (NJ) Bridge. The analysis results indicate that, after considering discontinuity geometric characteristics, 52.6% of the ISDRBs cannot form. Ultimately, 45 ISDRBs are identified, predominantly tetrahedron in geometry, and their volumes range from 0.02 to 32.57 (:{text{m}}^{text{3}}), with the majority being smaller than 5 (:{text{m}}^{text{3}}). A convenient and feasible evaluation method based on ISDRB information is finally proposed to further discuss the blocky rock mass system stability. In conclusion, automated extraction of ISDRBs can provide accurate quantitative references for rockfall disaster prevention and mitigation design.

The soft-hard interbedded anti-dip slopes (SHIADSs) in the reservoir area represent a type of layered anti-dip rock slopes characterized by unique rock layering in a particular geological context and are widely distributed. This study examines the failure evolution of a SHIADS, with an embedded thick-layered rock beam, in the Three Gorges reservoir area by applying the universal distinct element code (UDEC) under the combined effects of reservoir water softening and seepage. The simulation results indicate that the thick-layered rock beams within the slope play a critical role in influencing the failure process of the slope’s rock layers. Furthermore, the study investigates how the location and thickness of rock beams impact the deformation of SHIADSs within the reservoir area. As the rock beam’s location moves closer to the interior of the slope, the area of the slide body above the rock beam decreases considerably, while the area below the rock beam increases significantly. As the rock beam’s thickness increases, the area of the slide body above the rock beam decreases significantly, while the area below it remains largely unchanged. The forces in the rock beams are consistent with the independent cantilever beam model, and the changes in location and thickness are essentially changes in the tensile stresses in the rock beams. The findings of this study provide valuable guidance and reference for the reinforcement of SHIADSs in reservoir areas.

Landfilled waste exhibits strain-softening behavior at large deformations due to fiber failure and fluid-like transitions, complicating the identification of trigger mechanisms for landfill flowslides. This study presents an advanced numerical approach to address strain-softening and state transitions in landfill flowslide disasters. A solid-viscous constitutive model, which decomposes effective stress into solid and viscous stress components, is introduced. The solid-liquid interaction is modeled through coupled displacement-pore pressure formulations. Validation of the proposed model extends beyond prior field data to include ring shear tests, flowslide model tests and centrifuge experiments, ensuring robust assessment of viscous stress and the solid-viscous constitutive formulation. Two case studies involving heavy rainfall and high leachate level demonstrate the approach’s advantages. Under heavy rainfall, failure initiates above the wetting front due to the dissipation of matrix suction and weakening fiber embedment. In contrast, high leachate level-induced flowslides exhibit deeper failure surfaces and longer sliding distances. Complete slope failure occurs when the unsaturated waste reaches its peak strength, and the failure surface fully penetrates. These findings provide critical insights into the mechanisms driving landfill flowslides and offer guidance for risk mitigation strategies in waste management practices. 

Soluble salts significantly influence the freezing characteristic parameters of frozen soil. Previous studies have either insufficiently addressed the effect of sodium sulfate on matric suction or not comprehensively revealed the mechanism by which temperature affects matric suction at freezing temperature. In this study, the moisture and suction sensors were used to quantify the freezing temperature (FT), unfrozen water content (UWC), and matric suction (MS) of Ili loess with varying soluble salt contents. The impact of soluble salt content on three freezing characteristic parameters were investigated with the underlying mechanisms revealed. The results indicated that there was an initial decrease in both freezing and supercooling temperatures as the soluble salt content increased. Beyond a soluble salt content of 14 g/kg, an increase in both the freezing and supercooling temperatures was observed. Specimens with different soluble salt contents exhibited distinct UWC, which could be categorized into three stages based on temperature. A crystal precipitation stage was observed beyond the soluble salt content of 14 g/kg. Moreover, the proposed fitting model for UWC by incorporating the soluble salt content into the Gardner model demonstrated high accuracy. The MS can also be divided into three stages with temperature. Notably, specimens with soluble salt contents of 20 and 26 g/kg exhibited nonlinear increases in MS at temperatures of 5 °C and 10 °C due to crystal precipitation. Furthermore, theoretical calculations indicated the complete precipitation of sodium sulfate during the positive temperature stage.

The inverse graining deposit (IGD) resulting from landslides is frequently susceptible to seepage-induced erosion failure, posing a significant threat to infrastructure, exemplified by the Sichuan-Tibet Railway, as well as the local population. In this study, the phenomenon of fluid flow-induced particle migration within IGD has been examined through seepage tests utilizing a proprietary experimental apparatus and numerical simulations utilizing a coupled computational fluid dynamics-discrete element method (CFD-DEM) coupling scheme, focusing on elucidating particle dynamics and the underlying migration mechanisms. The experimental findings reveal that continuously graded IGD and discontinuously graded IGD are vulnerable to localized erosion and piping erosion, respectively. Furthermore, the critical hydraulic gradient for erosion diminishes with the reduction in fine particle content, unevenness coefficient, and hydraulic gradient in the lower layer. Numerical simulations are conducted to analyze the erosion mechanism and to assess the impact of fine particle migration and particle content on the overall stability. The findings from these simulations indicate that the absence of fine particles in the middle and upper layers of IGD leads to an inability to replenish particle loss in the lower layer, thereby exacerbating erosion. Consequently, IGD, particularly with those with discontinuous gradation, may play a pivotal role in promoting erosion behavior. It is imperative to conduct further research to examine the influence of layer number, gradation continuity, and the order of particle size distribution in situ, to assess the stability of the deposit under seepage conditions.

The rebound test, which measures the rebound height (R_H) to swiftly assess the uniaxial compressive strength (UCS) of rock, is a potential alternative to address the costly and time-consuming of traditional direct testing methods. However, practical applications have revealed significant predictive inaccuracies with rebound testing, raising doubts about the reliability of current standards and previously empirical equations. This study critically evaluates the reliability of the rebound testing standard and existing empirical equations using the N-type Schmidt hammer. A total of 482 rock samples from Western China was analyzed through a series of laboratory tests, indicating that the N-type Schmidt hammer causes a significant decrease in UCS, even leading to sample damage. Moreover, the choice of rebound testing standard substantially influences the testing results. Cross-validation of reference and laboratory data exposed regional variations in data distribution characteristics, and statistical analysis showed that existing equations, developed from limited data, are not universally applicable. To enhance prediction accuracy, this research proposes the use of wave impedance to characterize initial rock damage, thereby gives a practical physical significance to the predictive equation. This research contributes to the refinement of current rebound testing standards and presents a novel methodology for improving the accuracy of rebound testing in rock mechanics.