Bulletin of Engineering Geology and the Environment最新文献

Bedding plane, as an important structural feature of rocks, significantly affects the mechanical behavior of anisotropic rock. A good understanding of how bedding plane orientation affects deformation and strength properties is therefore crucial for better evaluation of stability in geotechnical engineering. In this study, the PFC3D software is used to investigate the combined effects of intermediate principal stress and bedding plane orientations (i.e., inclination and strike) on the strength and deformation behavior, and the associated micro-cracking processes within anisotropic rock under true triaxial stress condition. The results reveal that the inclination angle (IA) of bedding plane is a key factor determining the brittle-ductile transition behavior in the stress-strain response. Conversely, the strike angle (SA) of bedding plane has a negligible influence on the deformation behavior of the model. The simulated peak strength shows a typical U-shaped variation with the increase of IA at low SA (i.e., ω < 45°). However, the U-shaped variation of model strength gradually diminishes with increasing intermediate principal stress when SA is higher than 60°. In addition, the peak strength of the model is found to gradually increase as SA increases. On the other hand, with the increase of IA, the failure pattern undergoes a transition from being parallel to the σ₂ direction to being parallel to the bedding plane and finally returns to being parallel to the σ₂ direction. The findings of this study provide an essential basis for understanding the mechanism of how bedding planes affect the mechanical behavior of rocks under true triaxial compression.

Aiming at the difficulty in predicting deformation and evolution of high and large slopes in open-pit mines, this study proposes a new approach. Based on periodic ground radar monitoring images, we applied OpenCV technology and introduced a novel indicator—Cumulative Difference Degree of Image Data-Time (CDD-T)—to construct a landslide evolution description method. Verified at the south slope deformation area of an open-pit coal mine (Xilingol League, China), the method identified dangerous areas via nⁿ×nⁿ refined segmentation and CDD-T curve analysis: slope toe (+ 984 to + 960) and southwest side (+ 1030 to + 984), with potential traction-type landslide mechanism confirmed by CDD-T heat maps. CDD-T curves were highly consistent with cumulative displacement-time curves (minimum Pearson coefficient: 0.9326; average: 0.9629). Notably, 89% of CDD-T curves provided earlier warnings, offering new insights for open-pit mine landslide research.

Slope instability poses significant challenges in geotechnical engineering, necessitating effective mitigation strategies. Among these strategies, toe buttressing has emerged as a prominent method, involving the strategic placement of materials at the base of unstable slopes. However, the efficacy of toe buttressing remains insufficiently explored in scientific literature, particularly through the integration of real-time monitoring and numerical modeling. This paper explores the effectiveness of toe buttressing as mitigation measure for slope stability without the influence of additional stabilization methods. Through a combination of field monitoring, laboratory testing, and the finite element analysis, we assess the influence of toe buttressing on slope dynamics and stability under varying environmental conditions. The study site, located in a basalt quarry in Nentershausen, Germany, experienced a landslide, with the sliding plane located at the interface between basalt formations and the underlying clay layers. Our monitoring results demonstrate that the placement of a 10 m thick toe buttress effectively halted the movement of a 295,000 m³ landslide. Additionally, we investigated the impact of different buttress configurations and groundwater levels on the factor of safety (FoS) using a 2D finite element model. The results clearly show the important role that toe buttresses play in strengthening slope stability. Our study emphasizes the need for more detailed case studies focusing solely on toe buttressing as a means of stabilization. Such research is essential to develop statistical models that can determine the necessary buttress volume and height to support/stabilize different landslide scenarios. Additionally, we discuss the broader implications of our study and future research for slope management applications and underscore the need for interdisciplinary approaches to address the complexities of slope stability in a changing environment.

The adverse properties of soda saline-alkali soil often result in subgrade damage and slope instability. This study proposes the utilization of the zero-cost and environmentally friendly spent coffee ground (SCG) to improve the engineering properties of soda saline-alkali soil. The mechanical, physicochemical, and microstructural properties of SCG-improved soil were investigated through a series of tests. Results indicated that with increasing SCG content, the unconfined compressive strength, shear strength, and electrical resistivity increased, and the coefficient of compressibility, pH, cation exchange capacity, exchangeable sodium ion percentage, absolute value of zeta potential, and porosity decreased. The mineral composition was not changed with the addition of SCG. The pH reduction was due to the acidic functional groups in palmitic acid, stearic acid, and chlorogenic acid from SCG. K⁺ and Ca²⁺ in SCG exchanged with Na⁺ in pore solution, reducing the thickness of diffuse double layer and increasing the attraction between clay particles. Moreover, the palmitic acid, stearic acid, and their derivatives wrapped the soil particles to form larger agglomerated particles, which enhanced the cohesion and internal friction angle. This study demonstrates that SCG can be used to improve the engineering properties of soda saline-alkali soil, providing preliminary insights for green soil improvement.

Understanding the formation of collapse sinkholes in urban loess roads caused by dynamic loading and pipeline leakage is challenging in engineering geology and environmental investigations. The influences of dynamic loading on infiltration behavior and its collapse sinkhole-causing process remain elusive. Here, we evaluate the impacts of dynamic pro-infiltration and its sinkhole-causing process via physical and numerical simulation approaches. This allows us to estimate the critical physical and mechanical parameters that best describe water movement under the influence of vehicle dynamic loading and its disaster-causing effects. The results reveal that the infiltration behavior of the loess subgrade is enhanced by dynamic loading because of the acceleration of wet front migration, the increase in the infiltration rate, the increase in the pore pressure, and the aggravation of the erosion process. Moreover, these promotional effects are most remarkable when the frequency of the applied dynamic load is close to the resonance frequency of the subgrade soil. The formation of collapse sinkholes in urban loess roads due to dynamic pro-infiltration exhibits evolutionary features of three stages and five steps i.e., the cumulative stage of damage due to dynamic infiltration (saturated softening of seepage and vibration promoting infiltration fracturing), the stage of erosion loss due to dynamic loading–infiltration (vibration scattering and erosion, which causes penetration and vibration–collapse, which causes loss and holes) and the stage of dynamic infiltration promoting deterioration–shearing–impact collapses. In addition, the underlying causes of the formation and prevention strategies of typical collapse sinkholes in urban loess roads triggered by dynamic pro-infiltration are investigated. Our findings not only advance the understanding of sinkhole hazard occurrences in urban roads but also offer promising insights for creating safer, more resilient, and sustainable urban geological environments.

To address challenges in predicting and controlling vibrations arising from the non-stationary stochastic characteristics of blasting vibrations, a decoupled modeling approach is employed. The blasting vibration signal is decomposed into a coupled process comprising a non-stationary intensity component (characterized by a Gamma function) and a stochastic frequency component (represented by filtered white noise), establishing a predictive model for single-hole blasting vibrations. A multi-hole blasting vibration prediction model is further developed using Anderson’s superposition theory. Model parameters are optimized through stochastic search algorithms based on a comprehensive waveform similarity index (Z). Field experiments at two geologically distinct open-pit mines (Jiangxi and Beijing) demonstrate accurate waveform predictions for both single-hole and multi-hole models, validating their correctness and effectiveness. Statistical analysis of simulated waveforms reveals vibration reduction patterns under varying conditions. Results indicate that the vibration reduction rate generally increases with extended inter-hole delay times but exhibits an inflection point where improvement transitions from rapid to gradual. Under identical delay conditions: (1) The vibration reduction rate increases with blast hole quantity, suggesting optimized hole numbers enhance vibration control in short-delay blasting; (2) Larger blast center distances reduce vibration reduction efficiency, indicating that inter-hole delay adjustments alone cannot ensure effective suppression in far-field regions; (3) Higher longitudinal wave velocities improve vibration reduction due to amplified superposition effects in high-wave-velocity geological media.

While rainfall thresholds for landslide early warning and the exacerbating effect of post-earthquake rainfall on landslides are well documented, understanding the changes in rainfall thresholds for post-earthquake landslides and their application to regional-scale early warning systems remains challenging. This study proposes an integrated framework combining statistical and mechanistic modeling to quantify rainfall threshold variations pre- and post-earthquake, using historical landslide data, geological maps, and seismic records from Yadong County, Xizang, China. We first derived a 3-day cumulative rainfall threshold curve for pre-earthquake landslide. The Newmark model was subsequently applied regionally to back-analyze landslides triggered by the 2011 Sikkim earthquake, establishing post-seismic rainfall thresholds validated by a cumulative displacement distribution map (AUC = 0.81). Results demonstrate a 31.7% average reduction in post-earthquake cumulative rainfall thresholds, highlighting a more pronounced reduction in rainfall requirements for landslide initiation following seismic events. This study underscores the necessity of dynamic adjustments to rainfall thresholds considering seismic disturbances when devising early warning systems for landslide risk management across active tectonic regions in flood seasons.

Compared to hard rocks with low porosity, natural porous rocks and rock-like materials subjected to various weathering processes exhibit more pronounced nonlinear mechanical characteristics during compression, particularly during the initial stage of pore and crack closure. To characterize the influence of radial pressure on the nonlinearity in the mechanical behavior of porous rock-like materials, a phenomenological elastoplastic damage constitutive model under triaxial compression is proposed based on the Effective Medium Theory (EMT). By introducing the minimum principal stress as an independent variable to describe crack closure, this model overcomes the limitation of previous models, which require different material parameters for different confining pressure conditions. Furthermore, an initial damage state is defined, and a damage healing function, with the equivalent crack strain as an independent variable, is introduced to account for the variation in elastic modulus during the linear stage of uniaxial loading under different compression conditions. A stress-strain analytical algorithm for the two-stage (confining pressure-uniaxial compression process) is proposed based on the Newton-Raphson iteration method to determine the evolution of state variables prior to uniaxial loading, thus reflecting the impact of the confining pressure loading process. The model is validated as effective by this algorithm, and the stress-strain curve shows a good fit with experimental data, indicating that the model can effectively reflect both pore compaction and brittle-ductile transition behaviors of porous rock-like materials during the compaction stage under varying compression conditions using a single set of parameters.

The stress condition in the soil is one of the major concerns in understanding the responses of structures subjected to faulting. Although the soil stress in fault zones was investigated in field observations, theoretical studies, and numerical modeling, few of them measured the soil stress during faulting in tests. This study conducts both centrifuge modeling and theoretical estimation for soil stress in dry sand subjected to reverse faulting. The centrifuge test models the free-field condition under 50g. Miniature pressure sensors are installed to measure the horizontal soil stress on the footwall. A theoretical method for earth pressures under lateral deformations proposed in a previous study is applied to estimate the horizontal soil stress in this study. The results show that the horizontal soil stress on the footwall increases as it receives continuous horizontal displacements and compression initially. When the rupture develops, the displacements are localized in the shear band. The horizontal soil stress gradually becomes stable from the bottom to the rupture along the depth. The outcropping of the rupture is a critical state for horizontal soil stress. When the rupture outcrops, no more increments of soil stress occur on the footwall, as the fault deformation is released through the rupture path. The horizontal soil stress on the footwall has a D-shaped distribution along depth during faulting. The lateral earth pressure coefficient decreases from the rupture to the bottom with depth. The theoretical estimations of horizontal soil stresses generally agree with the measured ones.

As the key buffer material in deep geological repositories for high-level radioactive waste, bentonite experiences chemical interactions with alkaline solutions resulting from cement degradation during long-term repository operation. This study investigated the effect of alkaline solutions on GMZ bentonite through a self-designed diffusion experiment using NaOH and KOH solutions (pH 12–13.8). The results showed that some compositions of bentonite such as montmorillonite, quartz, and albite, were partly dissolved after a one-year test. While both alkaline solutions showed similar effects on bentonite, the KOH solution dissolved more montmorillonite and promoted the formation of illite. Ion exchange reactions between bentonite and alkaline solutions are evident at pH > 12.6, accompanied by reduced montmorillonite interlayer spacing. Microstructural characterization revealed that the montmorillonite interlayer collapsed under elevated pH conditions, generating some micro-cracks and holes that accelerate the mineral dissolution.