Bulletin of Engineering Geology and the Environment最新文献

In order to investigate the frequent water and mud inrush disasters caused by seepage instability in filling-type karst tunnels, the seepage instability mechanism of the water inrush channel under different fine particle contents is studied by mechanical analysis, laboratory testing and numerical simulation in the non-uniform filling-type karst tunnels. Firstly, a mechanical seepage instability model of the water inrush channel under different fine particle contents is developed. Secondly, the incipient particle motion mechanical test is conducted under different fine particle contents. Thirdly, the incipient particle motion and seepage instability of the channel under different fine particle contents are simulated by the CFD-DEM coupling method. Finally, the derived formulas for the incipient flow velocity are applied to the Junchang project. The main findings include that: (1) There is a nonlinear variation trend between the incipient flow velocity and the particle size, the incipient flow velocity initially decreases and subsequently increases with the increase of the particle size. (2) The shear strength of the particles decreases with the increase of the fine particle content, and the cohesion of the particles increases with the fine particle content. (3) The variable shape of the water inrush channel under different fine particle contents increases with the incipient flow velocity, and decreases with the increase of the fine particle content. (4) The main mode of critical instability for the particles is rolling instability. The error between the theoretical incipient flow velocity and the experimental incipient flow velocity in rolling instability increases with the particle size.

This paper experimentally examines the impact of high temperatures on the physical and mechanical properties of pre-damaged sandstone. Nuclear magnetic resonance (NMR) technology is utilized to observe pore evolution under combined preloading and thermal treatment. Uniaxial compression tests were conducted to evaluate the strength variation and damage mechanisms, while fractal dimension theory was applied to characterize pore structure based on NMR data. The results showed that high temperature and preloading treatments have a great influence on the internal pore characteristics of sandstone samples. After 400 °C treatments, the proportion of mesopores and macropores of sandstone decreases, while the proportion of micropores increases. After 600 °C treatments, the proportion of micropores and macropores of sandstone decreases, and the proportion of mesopores increases. The reduction of compressive strength of sandstone after 400 ℃ is mainly controlled by mechanical damage, while the reduction of compressive strength of sandstone after 600℃ is mainly controlled by thermal damage. The thermal damage of sandstone is related to the increase in the proportion of mesopores, which leads to the low strength of sandstone after 600℃ and decreases significantly with preloading ratio (The compressive strength decreased from 107.4 MPa to 72.8 MPa as the preloading ratio increased from 0.4 to 0.8). The larger the preloading ratio of sandstone after high temperature treatment, the smaller the fractal index D_NMR. And the D_NMR of sandstone after 600℃ is roughly positively linearly correlated with porosity, and the D_NMR of sandstone after 400℃ is roughly negatively linearly correlated with porosity.

Accurate landslide hazard prediction relies on well-calibrated models. Traditional single-objective calibration focuses on optimizing one model aspect—typically the final landslide condition—which can limit the model’s accuracy in representing overall landslide dynamics. In contrast, multi-objective calibration simultaneously optimizes multiple model aspects, being able to capture both antecedent and final conditions to enhance model performance. This study compares both calibration approaches within a physically based slope stability model applied to the Vall d’Aran region. Several calibration scenarios were proposed using an automatic calibration module. While the single-objective approach performed well overall, it struggled to accurately represent soil water dynamics. In contrast, the best multi-objective calibration scenario improved both the model’s accuracy and its physical representativeness, achieving accuracies of 91% and 72% for antecedent and final landslide conditions, respectively. Findings reveal that antecedent effective recharge and drainage area size significantly influence landslide susceptibility, with rainfall infiltration identified as the primary trigger. Additionally, groundwater response analysis indicated a response time of ~ 100 days, meaning that the effects of a single large rainfall event can persist for several months, leading to the generation of lateral flow and ultimately causing slope failure. The multi-objective calibration approach introduced here provides a novel, efficient approach, adaptable to data-scarce regions and applicable to similar models.

During enhanced geothermal system (EGS) development, granite masses undergo rapid thermal shocks, compromising their structural integrity. This study quantifies the deterioration mechanisms of granite under thermal shock through integrated NMR pore analysis, SEM fracture characterization, and triaxial compression tests. Key findings reveal: (1) Thermal damage primarily propagates through macropore enlargement (porosity increase > 50% at 600 °C) and microcrack coalescence; (2) Compressive strength and elastic modulus degrade exponentially with temperature (exhibiting 28% and 41% reductions at 400 °C relative to ambient conditions); (3) A novel damage-constitutive model accurately predicts stress–strain behavior (R² = 0.94) by correlating microcrack evolution with mechanical degradation. The validated model enables stability risk assessment in deep geothermal reservoirs, providing critical input for EGS wellbore design criteria.

The China-Nepal transportation corridor, a vital link, includes the western route of the China-Nepal Highway from Lhasa to the Jilong Border. This route has faced persistent engineering disturbance hazards since its construction in 1965, significantly compromising its safety. The planned China-Nepal Railway is set to be built largely in parallel to the existing highway. Therefore, a systematic study of the existing types, characteristics, triggering factors, and susceptibility zones of engineering disturbance hazards along the China-Nepal Highway can provide valuable insights for mitigating such hazards in future railway construction. Field investigation along the highway have cataloged over 160 hazard sites, classified into six main types: earth slides (14 cases), debris-bedrock binary slides (20 cases), earth-rock mixture slides (37 cases), earth-rock mixture falls (31 cases), rock falls (46 cases), and rock topples (13 cases). The susceptibility prediction model has been refined by applying the First Law of Geography to the hazards identified in field investigations. A comparison with ANN and Simple CNN models demonstrates that the proposed sample optimization strategy effectively enhances model performance. This strategy addresses the limitation in susceptibility prediction where point-format hazards fail to adequately represent the environmental characteristics of the entire hazard body. Results indicate two areas of extremely high susceptibility to engineering disturbance hazards along the China-Nepal Highway. The first area features rocky slopes with unloading fractures in broad river valleys, particularly where slate is exposed. The second area includes slopes of Quaternary loose deposits that have been disturbed by slope excavation in alpine valleys with heavy rainfall.

In the process of coal seam mining, the fault structure can easily lead to the concentration of ground stress, which seriously threatens the safety and efficiency of mining. In order to study the influence of repeated mining on the subsidence law, fracture characteristics and stress distribution of overlying strata under the condition of reverse fault, this paper adopts the method of similar simulation and numerical simulation to analyze the subsidence, fracture and stress variation law of overlying strata, and optimize the gas extraction effect in the goaf. The results show that the more downward mining, the more obvious the collapse and compaction of overlying strata of coal seam; the sinking amount of the reverse fault shows “M” distribution in the displacement change of various heights under the influence of fault mining, and the sinking amount shows “n” distribution in the mining of faultless coal seam; The stress of coal seam overburden presents a small-large-small distribution state; in the overburden rock subsidence law, the maximum subsidence range of the reverse fault is concentrated in the central Goaf; in the stress evolution law of reverse fault mining, the stress transfer phenomenon of weak structure body of coal rock mass cracking appears; the effect of gas extraction in goaf is optimized, and it is concluded that negative pressure extraction is adopted in goaf, and the negative pressure of orifice extraction is 7.6 KPa; the amount of gas extraction from high-level boreholes accounts for 30.2% ~ 55.4% of the total gas emission. The research results can provide a reliable basis for future mining under fault structures.

The shear characteristics of the subglacial debris-clean ice interface (SDCI) play a critical role in glacier stability. Increasing global warming has amplified glacier-related geohazards, posing significant risks to infrastructure and communities. This study provides the first systematic experimental investigation of the SDCI under coupled thermo-mechanical forcings, addressing critical gaps in understanding shear behavior at ice contents exceeding 40%. Through cryogenic direct shear tests, we quantify the roles of temperature (-9 °C to -1 °C), ice content (40–90%), and normal stress (150–550 kPa) in governing failure modes, stiffness degradation, and strength thresholds. Key findings reveal that SDCI shear behavior is more sensitive to temperature variations than to ice content or normal stress. As the temperature increased from − 9 ℃ to -1 ℃, peak shear stress and shear stiffness decreased by approximately 80%. Shear performance degradation is more pronounced at lower ice contents. Critical thresholds for temperature and ice content were identified, marking transitions from strain-hardening to softening and further to elastic-brittle failure. A disturbed state concept (DSC) model, integrating linear and hyperbolic characteristics, was developed to simulate the shear stress-displacement relationship, supported by parameter sensitivity analysis. Additionally, an improved Mohr-Coulomb strength criterion was proposed to account for the effects of ice content and temperature on cohesion and friction angle. These advances provide a framework for predicting SDCI behavior under climate-driven thermal fluctuations.

The maximum impact force (F_max) and maximum penetration depth (δ_max) are critical parameters in the design of rockfall protection structures. Current methods for calculating rockfall impact force often simplify the rockfall as a sphere, thereby neglecting the significant effects of rockfall shape and impact angle, which can lead to estimation inaccuracies. Through experimental and numerical analyses, we demonstrate that the F_max occurs at a 90° impact angle, with the F_max of an ellipsoidal rockfall (sphericity = 0.6) being 1.42 times greater than that of a spherical rockfall. Conversely, at a 0° impact angle, the δ_max of ellipsoidal rockfall is 1.72 times greater than its spherical rockfall. This phenomenon indicates that calculating impact force by assuming a spherical rockfall shape may underestimate the actual impact force, resulting in inadequate safety of the protective structure. Based on these findings, we propose two innovative calculation methods for evaluating the F_max and δ_max exerted by an ellipsoidal rockfall impacting a sand cushion. The first method proposes the shape magnification coefficient, and establishes the quantitative conversion relationship for F_max and δ_max between ellipsoidal and spherical rockfalls through experiments and simulations. The second method, based on Hertz contact theory, the analytical solution including shape parameters is derived. The suggested values of F_max and δ_max for ellipsoidal rockfalls are given. Verification indicates that new models enable more accurate prediction of F_max and δ_max for ellipsoidal rockfalls. The results can be applied to the design of protective structures such as shed tunnels, effectively enhancing the accuracy and economy of rockfall disaster prevention and control.

Thermal shock from high temperatures and prolonged heat exposure can cause irreversible damage to natural stones, underscoring the need for thorough characterisation. This study examines the effects of thermal exposure at 300 °C and 600 °C, temperatures simulating moderate and high thermal shock, on thirteen carbonate lithologies, including limestones, marbles, travertine, and breccia. Key surface properties, colour, gloss, and roughness, are evaluated to quantify aesthetic impacts and understand the underlying chemical and mineralogical processes. FeO-richer stones show significant increases in the a* coordinate (up to Δa* = +34.37) at 300 °C, driven by the transformation of goethite into hematite. In contrast, stones richer in organic matter exhibit marked decreases in lightness (up to ΔL* = −18.78) at 600 °C, due to the transformation of amorphous organic matter into crystalline phases. Porosity plays a critical role at higher temperatures, correlating with higher ΔL* values, since more porous stones enhance heat transfer and promote the combustion of organic matter. Lightness is influenced by both gloss and surface roughness, with gloss having a more pronounced effect on L*. Statistical analyses, including Tukey’s HSD test, reveal significant differences in stone responses to thermal shock, highlighting their varying degrees of thermal susceptibility. Principal Component Analysis (PCA) identifies colour as the main driver of variability, followed by gloss and roughness. These findings provide a predictive framework for assessing the thermal vulnerability of carbonate stones in relation to their residual composition and texture. Such insights support informed decisions in material selection, conservation strategies, and architectural design, thereby enhancing the long-term durability of natural stones in both heritage and contemporary contexts.