Bulletin of Engineering Geology and the Environment最新文献

This study aims at developing a site similarity characterization method suitable for the site-specific data scenario. The site-specific data is generally multivariate, unique, sparse, incomplete, corrupted, and has temporal and spatial variability, briefly denoted as MUSIC-X. Considering the strong power of Bayesian theory in handling uncertainty, the Bayesian inference framework is employed to build the site-specific multivariate distribution model to characterize the site. Then, by combining the site-specific multivariate distribution model and the image structural similarity (SSIM) theory, a site similarity characterization method under site-specific data scenario is proposed. This proposed method was demonstrated by a real site-specific data in Onsøy site in Norway. The results show that (i) the proposed method can obtain the monotonic site similarity indicator with a range of [0, 1], (ii) site similarity can be assessed from three statistical perspectives, namely mean, standard deviation, and correlation, (iii) the proposed method allows for quantifying the uncertainty associated with site similarity characterization, and (iv) spatial correlation of geo-material parameters can be considered. Besides, the link between similarity and engineering characteristics of sites is revealed by a case study about the bearing capacity analysis of the shallow buried footing foundation.

Soil-rock mixtures in fault fracture zones are composed of rock blocks with high strength and fault mud with low strength. In this paper, in order to study the mechanical properties of the soil-rock mixture with non-cohesive matrix, a large-scale laboratory triaxial compression test with a specimen size of 500 mm×1000 mm is conducted, combined with numerical simulation analyses based on the two-dimensional particle flow software PFC2D. The macroscopic mechanical response and mesoscopic fracture mechanism of soil-rock mixtures with varying rock block proportions, block orientation angles and matrix strengths are studied. The results indicate the following: (1) When the proportion is less than 30%, the shear characteristics of the mixture are similar to those of its non-cohesive matrix. When the proportion is in the range of 30-70%, the internal friction angle and cohesion increase rapidly, and the softening characteristics of the mixture become more apparent. When the proportion exceeds 70%, the aforementioned effect slows. (2) The strength of the mixture is positively correlated with its matrix strength, and the influence of the matrix strength on the loading curve of the mixture is related to the block proportion. (3) When the block orientation angle is 0°, the cohesion and internal friction angle are slightly greater than those at an angle of 90°. Based on the above, for the soil-rock mixture with non-cohesive matrix, a strength prediction model based on the block proportion is given when the block orientation angle and matrix strength are consistent.

Landslides triggered by rainfall are complex phenomena influenced by a multitude of condition and trigger factors. A significant challenge in the field is the accurate and interpretable assessment of large-scale landslide hazards, particularly due to the lack of consideration for the synergistic effects of multiple triggers and spatial heterogeneity. This study introduces a novel regional hazard assessment method that leverages geographic similarity to address these challenges. Our approach consists of four key steps: (1) extraction of sample information from relevant data based on the historical distribution of landslides and their influencing factors, (2) application of a scale-space algorithm to manage spatial heterogeneity, with a partition scale determined by the q-value variation, (3) optimization of sample configuration and generation criteria under the guidance of geographic similarity for enhanced spatiotemporal modeling, and (4) utilization of machine learning models to refine inductive bias and capture nonlinear relationships, enabling a quantitative estimation of hazard probabilities for each slope unit within the prediction module. We applied our P-RF + method to Yunnan Province, China, incorporating 11 condition factors and 7 trigger factors across 624 historical rainfall-induced landslides and 1248 non-landslide cases. Comparative experiments reveal that the P-RF + model substantially outperforms existing methods in accuracy and interpretability. Furthermore, a case study during the rainy season illustrates the model's capability to provide timely warning instructions for rainfall-induced landslides. These findings underscore the potential of our proposed method to offer valuable insights for disaster prevention decision-making.

Graphical Abstract

Using a two-order profile to characterize the concrete/rock interface, this paper proposes an analytical solution for the shear behavior of the concrete/rock interface under constant normal stiffness (CNS), taking into account the interlocking effect and wear behavior. The interlocking effect of second-order asperities is reflected by considering the work and energy, and the analytical expression of wear behavior is obtained by geometrically decomposing the worn rock asperity into finite tiny triangles. Subsequently, the proposed analytical model, consisting of the elastic stage, the sliding stage, and the progressive damage stage, is substituted into the load-transfer governing equation, and the bearing characteristics of rock-socketed piles are figured out by taking advantage of the finite-difference method. Finally, a parametric analysis is conducted to investigate the effects of second-order asperity distribution parameter (eta), wear coefficient (xi), and first-order asperity angle ({alpha }_{0}). Both laboratory CNS direct shear tests and field vertical load pile tests are selected to verify the reliability of the proposed analytical model. The results indicate that the proposed analytical model can effectively reflect the variation characteristics of the shear stress-displacement curve and the normal stress-displacement curve under CNS conditions, and its application in the load-transfer behavior of rock-socketed piles can well predict the bearing characteristics.

The sliding friction angle is a fundamental mechanical property both for intact and jointed rocks. The aim of this paper is to compare the value of sliding friction angle obtained from direct shear tests on rock fractures and that obtained from triaxial compression tests on intact rock cores. For this reason, 286 direct shear tests were carried out on artificial rough tension fractures of ten different rock types under normal stresses 5 kPa − 2 MPa, using the multistage shear procedure with repositioning of the joint before each shearing. Another 112 conventional triaxial compression and unconfined compression tests were carried out on NX size (54 mm) intact specimens from the same rock types under various confining pressures up to 70 MPa. The sliding friction angle from the direct shear tests was determined from the measured peak friction angle and the corresponding dilation angle and that from the triaxial compression tests from the stress state at the estimated brittle-ductile transition. The results show that the values of the sliding friction angle of the studied rocks determined by the two methods are approximately equal (differences < 1°) and agree very well with well-established experimental data for similar types of rocks reported in the literature. They ranged between 32.5° and 40.2° with those of the weaker and more ductile carbonate rocks to be distinctly higher (35.4°-40.2°) than those of the stronger and more brittle silicate ones (range 32.5°-35.6°). The average transition principal stress ratio was 5.7 for carbonate and 4.1 for silicate rocks.

Compacted loess is widely used in construction and road engineering in the Loess Plateau region. It inevitably undergoes vertical deformation and desiccation-induced cracking due to environmental effects. This study investigates the deformation and cracking characteristics of compacted loess under vertical pressure during desiccation. Samples with initial water contents ranging from 5% to saturation are prepared for desiccation under vertical stresses of 0−100 kPa. Changes in resistivity are simultaneously monitored during desiccation. After desiccation, the microstructural characteristics of the soil are examined using X-ray computed tomography (CT), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) techniques. The effects of initial water content and vertical pressure on vertical strain, drying cracks, and electrical resistivity of compacted loess are analyzed. The results indicated that high vertical pressure and water content lead to significant compressive and desiccated deformation of compacted loess, which is reflected in the microstructure by a smaller pore size distribution (PSD). Lower initial water content and higher vertical load are more effective in suppressing cracking during the desiccation of compacted loess. The surface crack ratio (R_sc) of compacted loess is reduced by 99.54% as pressure increases from 0 to 100 kPa and water content decreases from saturation to 5%. The directions of cracks in loess during desiccation and the microstructural changes caused by deformation are effectively characterized by resistivity measurements. This study explores the variations in mechanical properties during desiccation of compacted loess and provides a theoretical foundation to use resistivity for characterization.

Owing to its high flexibility and low permeability characteristics, clayey soil has been largely used as impermeable material in pollutant burial fillers. Soil permeability is very sensitive and highly pertains to its microstructure. When subjected to the saline environment changes, the changes in soil permeability may increase leakage risk in the burial fillers and endanger the environment. Herein, to facilitate the understanding of the negative correlation between the permeability and ion concentrations in some low plastic limit clays, NaCl solution seepage circulation experiments considering different porosities, sample preparation methods, and ion concentration stages were conducted. Combined with the micro test methods (SEM and MIP) and the fractal theory, the changes in soil permeability at different ion concentrations and the mechanism were studied. The main results showed that compression methods are more suitable than the impact-involved methods for making uniform soil samples; the decrease of the soil’s pore fractal dimension evidenced that the growth of ion concentration would increase the dispersal of soil particles while the morphological change of the dispersal process resembles the blossom of a flower, i.e., the sprout→bud phase→blossom; the dispersed particles are prone to form flocculation in large-size pores (6–8 μm in this paper) and decrease the soil permeability. This dispersal and flocculation effect progressively triggered by the growth of ion concentration can provide new insight into understanding the negative correlation between the permeability and ion concentrations in some low plastic limit clays.

Landslides formed in rock with bedding and weak layers threaten the environmental safety of the Yellow River Basin in China. Further study of the creep mechanism of such landslides will help to evaluate their stability. In this study, field investigation, data monitoring, basic parameter tests, and expansion pressure test are combined. The failure characteristics and mechanism of the Luoquan (LQ) landslide in Zezhou, Shanxi, China, under natural rainfall conditions are analyzed in detail. The creep deformation of the LQ landslide occurred continuously during the period of meteorological rainfall concentration. Natural rainfall was the main triggering factor of the long-term creep deformation of the LQ landslide. With increasing saturation degree and time of the slide zones, the creep deformation of the LQ landslide was caused by weakening of the shear strength and expansion of the slide zones, causing cracks in roads and houses built on surfaces. When the natural rainfall decreased, the weakening, softening, and expansion mechanism of the slide zones weakened. The stability of the LQ landslide increased, and the creep deformation gradually stopped. As of now, the creep deformation rate of the LQ landslide, currently increasing, is likely to develop into complete destabilization. Therefore, the on-site monitoring of the LQ landslide needs to be continued.

Dramatic changes in temperature and rainfall with global warming can significantly alter the moisture status of topsoil, thereby inducing soil structure degradation. However, few studies have reported the variation in permeability of saline soils during drying, which contributes to further refining the mechanism of wetting‒drying effect on soil properties. In this study, the permeability and microstructure of sodic-saline loessal soil with different initial water contents (IWCs) and salt contents (ISCs) obtained from pre-saturation and subsequent drying were explored using constant head permeability tests and SEM observations. The results show that the permeability coefficient decreases exponentially with time. The maximum permeability coefficient (K_max) of the samples decreases with decreasing IWC and ISC, while the relatively stable permeability coefficient (K_rs) is less affected. The microscopic results show that during the seepage process, the porosity and pore diameter of samples with low IWC gradually decrease, accompanied by a weakening of pore directionality and an increase in fractal dimension. In contrast, samples with high IWC show an initial increase followed by a decrease in porosity, pore diameter and pore directionality, alongside a gradual decrease in fractal dimension. The drying process promotes the formation of inter-aggregate pores and weakens aggregate stability, leading to significant microstructural disturbances in low IWC samples upon rewetting. The increase in salt content enhances particle cementation but also creates additional channels for rapid permeability. These findings carry practical implications for the prevention and control of soil erosion and engineering geohazards in saline soil regions under the impact of climate change.

The mechanical behavior and deformation characteristics of gray sandstone greatly affect the stability and safety of large-scale structural engineering on the rock stratum. A series of tests for sandstone collected from Jinping hydropower stations in southwest China under complex stress paths were carried out, including hydrostatic pressure test, conventional triaxial test, cyclic loading and unloading of deviatoric stress, confining pressure and pore pressure test. Meanwhile, a fractional elastoplastic damage model was proposed. The results show that the crack closure stress, crack initiation stress, and crack damage stress under conventional triaxial compression path are 0.189~0.217, 0.475~0.615, and 0.730~0.856 of peak stress, respectively. The influence of cyclic loading and unloading on mechanical behavior and deformation of gray sandstone has a significant strengthening effect. Under deviatoric stress cyclic loading and unloading, with increasing cycle number, axial and lateral strain increment curves tend to coincide, and the volumetric strain increment decreases. Under confining and pore pressure cyclic loading and unloading, the lateral strain increment is much larger than the axial strain increment. The axial elastic modulus and lateral elastic modulus show great discretization and irregularity. Moreover, a modulus-like axial coupling parameter is analyzed and discussed. The established constitutive model can accurately reflect the hardening and plastic dilatancy behavior of gray sandstone. Meanwhile, the staggered iterative return mapping algorithm is improved to ensure the convergence of the model.