Bulletin of Engineering Geology and the Environment最新文献

Strong earthquakes in Chile are often associated with cascading hazards, such as ground shaking, liquefaction, tsunamis, and coseismic landslides. This study set recommendations for preparing earthquake-induced landslide inventories and developing and reporting an updated comprehensive earthquake-triggered landslides inventory of the 2007 M_w 6.2 shallow crustal Aysén earthquake. 781 landslides were re-mapped over a total area of c.1,350 km², based on unified earthquake-triggered landslide mapping criteria. The total landslide volume is c. 122.3 Mm³. 18% of earthquake-induced landslides were concentrated within 0–1 km of seismic faults, and 55% within 0–5 km. In addition, 53% of the landslides started in the upper quarter of the slope, while over 86% started in the upper half, which suggests that larger ground motions due to topographic site effects influenced the triggering of landslides during the shallow crustal earthquake. Hence, the distance to the rupture plane of faults is a first-order factor in the distribution of landslides together with topographic amplification site effects.

The freeze-thaw cycle poses a significant threat to foundations and roadbeds in seasonally frozen regions. This article conducts model experiments to analyze changes in the temperature field, water migration patterns, and settlement deformation characteristics of sand-gravel replacement foundations during freeze-thaw cycles. The experimental findings indicate that the low-temperature zone primarily exists within the sand-gravel replacement layer at the base of the slope. As the number of freeze-thaw cycles increases, the freezing depth of the sand-gravel replacement layer continues to rise. During the cooling phase, changes in soil volume moisture content result from self-weight and water migration during freezing. With an increase in the number of freeze-thaw cycles, the moisture content of external measurement points on the embankment rises at the end of the freezing period, whereas the moisture content of internal measurement points decreases. At the end of the thawing phase, measurement point 6 experiences an increase in moisture content due to the upward migration of water in the lower soil layer, while other measurement points exhibit reduced moisture content. The foundation’s settlement deformation exhibits a horizontal “tilted” shape, with cumulative settlement amounts and settlement deformation rates determined at various positions. These results suggest that the settlement deformation tends to stabilize one month after the completion of embankment filling construction. The maximum freezing depths at the left and right slope toe positions are 1 m and 1.2 m, respectively. Furthermore, the maximum frost heave at the slope toe position is less than the maximum thawing settlement, illustrating the irreversible soil deformation following freeze-thaw cycles.

Non-bedding fissures are common internal defects in layered slopes and often exert control over the slope's stability. In this study, a research on the failure mechanism of anti-dip bedding rock slopes (ABRSs) with two sets of non-bedding fissures was conducted based on fracture mechanics theory and the ABRSs cantilever beam model. Through centrifuge test, the rationality of this calculation method was verified, and the instability evolution mechanism of anti-dip bedding rock slopes containing internal defects was investigated. The research findings demonstrate that the instability of ABRSs containing non-bedding fissures goes through several stages, including tension of the rear rock layers, reverse bending of the rock layers, formation of the main fracture plane, and secondary failure. The initiation pattern of rock bridges between fissures significantly affects the post-failure deformation of rock layers. Additionally, tensional failure at gentle-dip fissures, occurring under shear action, is the main cause for inducing reverse bending of the fractured rock mass. This eventually leads to the formation of a stepped main fracture plane, resulting in the evolution of the slope into a reverse bending collapse zone and a block-reverse bending collapse zone. At approximately one-third of the slope height, the residual sliding force of the rock layers reaches its maximum, which is also the location where fissure deformation is most prominent and the stress situation is most complex. Moreover, the stability of ABRSs containing non-bedding fissures is more sensitive to the internal friction angle between rock layers, the length of non-bedding fissures, and the angle between fissures and rock layers.

In this paper, we present the construction of a geomechanical conceptual model for Permian–Triassic reservoirs of the Persian Gulf, achieved through a comprehensive comparison between geological facies, wireline data, and geomechanical parameters. Integrating geological and geomechanical data enabled the spatial distribution of key geomechanical parameters and the development of a conceptual model. This model offers valuable insights into the mechanical behavior of the various parts of the reservoir. Our database includes petrographical analysis of 1577 thin sections of 403 m of cores, routine core analysis, wireline logs, and geomechanical data in one well. Also, wireline logs from 6 other wells were used for correlation. Thin section studies showed 12 microfacies that have been deposited in a ramp depositional environment. Geomechanical data including Young modulus (E), Poisson ratio modulus (ϑ), shear modulus (G), bulk modulus (K), Schmidt hammer, and unconfined compressive stress (UCS), compared with geological and petrographical results. Electrofacies were constructed with the use of wireline log data. The incorporation of geomechanical data allowed for the construction of five geomechanical facies. The geomechanical features exhibit a progressive increase from one to five, indicating an inverse relationship with the reservoir quality of the electrofacies. Geomechanical units were defined by grouping similar geomechanical facies. Then, a relationship was established between geomechanical units and sea level changes. Subsequently, these units were correlated with sequence stratigraphic units and matched across the other six wells through the utilization of wireline logs. The spatial distribution of geomechanical units was determined by establishing their correlation with both geological facies and sequence stratigraphic units. Each geomechanical unit corresponds to the same depth interval of a systems tract belonging to a third-order sequence and a complete fourth-order sequence. This enabled us to detect and analyze the variations in the distribution patterns of geomechanical properties across the study area.

The failure behavior of rocks is complex due to the existence of random microscopic defects. This paper presents a new statistical damage model based on the modified Hoek-Brown criterion, i.e., the Pan-Hudson criterion, for predicting the mechanical characteristics of quasi-brittle rocks under compression, and demonstrated its predictive performance for medium-strong rocks. The lognormal distribution is incorporated to validate and reveal the statistical nature of internal microscopic defects. Its effectiveness in describing microscopic defects evolution is highlighted by comprehensive discussions on characteristic distribution parameters, which are rigorously derived. The degradation effects of microscopic defects on macroscopic mechanical responses are reflected by establishing the quantitative relation between damage variables and compressive strength. To validate the proposed model, a series of triaxial compression tests on sandstone are conducted. The peak strength and quasi-brittle post-peak behavior under various confining pressures are well captured. Sensitivity analyses on mechanical and characteristic distribution parameters are also carried out to develop an intuitive understanding of how the introduced modifications affect the mechanical responses. Finally, the deviatoric stress-axial strain curves were compared between our testing data of limestone and previous study. The advantages in capturing peak intensity and simulating the post-peak behavior of the proposed model is emphasized.

The Fenwei Basin has developed more than 600 ground fissures of different scales, with the Ground Fissures on Marginal Mountainous Region (GFMMR) in the Basin cause the most severe damage. However, there is currently limited research on the common characteristics of GFMMR, and the formation mechanisms are not yet clear. This study utilizes geological surveys, trenching, drilling, geophysical exploration, interferometric synthetic aperture radar (InSAR), and numerical simulation, found that the GFMMR develop on the hanging wall of the marginal mountainous faults, with their strikes generally consistent with these faults, and the failure pattern of these ground fissures that near the mountain is primarily shear failure, gradually transitioning to tension failure at the distal end. Profile results show clear synsedimentary fault characteristics, and these ground fissures are connected to deep-seated faults. This study reveals that the formation mechanisms of the GFMMR in the Fenwei Basin involve two aspects: fault control and hydrodynamic triggering. The extensional stress in the NW–SE direction of the Basin, combined with the counterclockwise rotation of the Ordos block, leads to the extensional creep of the marginal mountainous faults, further controlling the exposure locations and activity intensity of the GFMMR. Human overpumping of groundwater induces uneven subsidence of the stratum, forming a series of subsidence funnels on the surface, which exacerbates the rupture and expansion of ground fissures while also accelerating their exposure through water erosion caused by rainfall. This study has essential reference value for disaster prevention and reduction of ground fissures in the Fenwei Basin.

Landslides, among the most common natural catastrophes, pose significant risks to life and property. Uncertainties in soil strength and ground motions are widely reported to notably affect the landslide runout process. Existing research has predominantly focused on the influence of either non-uniform soil strength or stochastic ground motions, often limited to two-dimensional (2D) analyses. This research thus introduced a three-dimensional (3D) finite-element computational framework to explore the combined effect of these two factors on landslide runout distance, via coupling the coupled Eulerian–Lagrangian (CEL) large-deformation technique, random field approach and stochastic vibration theory. The results demonstrate that stochastic ground motions contribute to significant randomness in the runout distance, and soil heterogeneity further amplifies both mean value and variation of runout distance. This underscores the importance of considering the combined effect of random soil strength and stochastic ground motions on landslide runout. Furthermore, our comparison between 2D and 3D random analyses suggests that 2D random analysis tends to yield conservative results for a non-uniform soil slope, emphasizing the advantage of the established 3D large-deformation modelling of landslides. This research provides some valuable insights into the risk assessment of landslides, considering both non-uniform soil strength and stochastic ground motions.

Biochar is widely used for the improvement of soil in farmlands. However, the effect of biochar from different feedstocks on property changes during loess desiccation remains unclear. In this study, four types of biochar, including sludge biochar (SBC), wood biochar (WBC), cow dung biochar (CDBC), and corn straw biochar (CSBC), were mixed with loess from the top layer of the wheat field at concentrations of 0%, 5%, and 10%. Their impacts on loess soil evaporation, cracking, CO₂ emissions and electrical resistivity during desiccation were evaluated and microstructural changes after desiccation were analyzed. The results showed significant improvements in water retention with the addition of biochar, especially with CSBC, which prolonged the drying time. The addition of biochar suppressed cracks formed during loess desiccation, with CSBC having the most significant effect, reducing the crack intensity factor (CIF) by 70.47% and 89.01% for CSBC5 and CSBC10, respectively. The mean CO₂ concentration during desiccation decreased for only three specimens (CSBC5, SBC5 and CDBC10). The CO₂–C fluxes after the addition of biochar were not lower than those of pure loess. The addition of biochar reduced soil resistivity and altered the pore size distribution (PSD) of loess. Biochar from different feedstocks improves water retention and inhibits cracking to varying degrees during loess desiccation, with 5% CSBC proving to be the most effective in optimizing soil properties. The electrical resistivity effectively characterizes the macroscopic and microscopic variations in loess.

Landslides are natural disasters that are difficult to control without continuous monitoring. Xiji County is located in the southern mountainous area of Ningxia Hui Autonomous Region, where geological and ecological conditions are complex and the number and extent of landslides hinder local economic development. To address this, a comprehensive landslide inventory was created, comprising 529 historical landslides and an equal number of non-landslide points. Thorough analysis of these datasets ensured an unbiased assessment. The data was randomly divided into training (70%) and validation (30%) sets. Using 15 spatial datasets, including elevation, slope, curvature, distance to various features, rainfall, land use, lithology, and maximum ground acceleration, a system for landslide susceptibility evaluation was established with 12 influential indices. The frequency ratio method was applied to analyze the relationship between landslides and each index. Three evaluation models (LR, NB, and RBF Network) were built, utilizing different landslide characterization methods (landslide point and landslide polygon), resulting in six result maps for landslide susceptibility evaluation. Statistical analysis of frequency ratios in susceptibility class intervals ensured model rationality. The NB model based on landslide polygons showed optimal performance with high success rate (AUC = 0.965), prediction rate (AUC = 0.886), consistency (FRA = 0.873). This methodology and landslide susceptibility map provide decision-making support for researchers and local governments in mitigating future geological hazards.

Expanding on the challenges of expansive soils to civil infrastructure, this research delves into the synergistic application of microbially induced calcium carbonate precipitation (MICP) through bio-stimulation and natural fiber reinforcement to mitigate soil swell-shrink behavior and enhance soil strength. This research diverges from traditional methods by addressing their economic and environmental limitations. The dual strategy of bio-stimulation with natural fiber reinforcement was assessed through laboratory tests, including unconfined compression, 1D swell, linear shrinkage tests, and microstructural analysis. This methodology involved preparing solutions to foster bacterial growth and strategically adding jute fibers to enhance the soil matrix. Results revealed significant improvements in soil strength (up to 186%), and reductions in swell strain (up to 85%) and swell pressure (up to 90%), with the optimal jute fiber content at 1.5%. Additionally, a significant increase in calcium carbonate content (163–176%) highlighted bio-stimulation's role in soil stabilization. SEM analysis showed that bio-stimulation and jute fiber reinforcement transformed the soil microstructure, enhancing cohesion and reducing deformability. These outcomes highlight the promise of combining bio-stimulated MICP with natural fiber reinforcement as an eco-friendly and efficient approach to soil stabilization. They also add to the growing body of knowledge on tackling the issues posed by expansive soils in civil engineering applications.