Bulletin of Engineering Geology and the Environment最新文献

In recent years, ecological engineering has become increasingly important in slope protection under climate change. Plants roots can enhance shallow soil strength, reducing the probability of shallow landslides. Predicting the shear strength of root-reinforced soil is crucial for slope stability analysis. Most existing models, which were based on Wu model, assumed roots failed in tension. However, experiments show that roots are often pulled out rather than broken in shear tests, causing the overestimation of shear strength. This paper proposed a modified shear strength prediction model based on the pullout phenomenon of roots during shearing. The model defined total strength of root reinforced soil as the sum of inherent soil strength and additional resistance from root-soil friction, also considering soil suction effect. Direct shear box tests were conducted for alfalfa root reinforced Yili and Yangquan loess in China, examining the effects of root area ratio and root diameter. Results showed that alfalfa roots could increase loess shear strength. For a given root diameter, soil shear strength increased with root area ratio. However, at a consistent root area ratio, the increasing of root diameter led to the decrease of soil shear strength. The shear strengths of two root-reinforced loess soils were predicted using four different approaches, including Wu, Ning, energy-based models, and modified model in this paper. Compared to Wu, Ning, and energy-based models, the proposed model yielded superior accuracy with more accessible parameters, particularly demonstrating robust performance for larger-diameter roots.

Rockfall is one of the most abundant slope instabilities, which affects the engineering structures and planning of residential areas. There are several reasons and parameters which control the rockfall mechanism which should be evaluated in a wide perspective. A crowded part of Mardin city is located close to the ancient castle which is still in use for touristic purposes. Recent rockfall cases have caused severe damage to the structures around. Limestones and dolomitic limestones of Early Eocene aged Gercüş Formation and Early Oligocene aged Midyat Group are the main geological units in close proximity. The study area is formed by a steep slope with one kilometer length. Numerous fallen blocks spread around flat sections and possible blocks prone to rockfall have been detected by field studies and high-resolution images obtained from unmanned aerial vehicle (UAV) monitoring. The area has been divided into five sections to perform discontinuity characterization, also taking the slope geometry into account. Exact locations of the fallen blocks and the blocks on the slope have been determined using the UAV images. Digital slope, slope direction and geological maps have been prepared using point cloud data. This study aims to evaluate the rock fall hazard for the whole area based on imagery, numerical modelling and 3D rockfall analysis for considering protection measures. Combining the field work, imagery and mechanical properties of the limestones, 3D rockfall analysis have been performed and reinforced embankments have been offered with the evaluation of their performance.

In modern pile foundation drilling operations, rotating drilling tools leave a series of irregular joints on rock surfaces. Currently, there are certain limitations in research on the roughness of rock joints. For a more accurate quantification of the roughness of a rock joint under rotary-drilling conditions, the geometry of the rock joint surface was obtained using a three-dimensional non-contact high-precision laser scanner. Twenty joint surface contours were intercepted along the shear direction of the XZ system. The mean height h₀ and root mean square (RMS) σ of the centerline reflect the undulation characteristics of the joint surface, and the average inclination angle ({overline{theta }}_{text{p}}), which reflects the steepness of the joint surface, is extracted using the contour lines. The method of quantizing roughness with L/L₀ was extended to the three-dimensional space S/S₀, and the functional relationship between the three-dimensional joint roughness coefficient (JRC) and σ, ({overline{theta }}_{text{p}}) was obtained by bivariate fitting, and the goodness of fit reached 99.46%. The results of two real examples and laboratory direct shear tests demonstrate that the proposed method is similar to other methods, and the numerical variation trend is more stable than that of the classical method, which verifies the feasibility of the proposed method.

Freeze-thaw cycles in cold regions often induce severe deterioration in saline subgrade soils due to their geological and environmental sensitivity. To address this, low-carbon, resource-efficient stabilization methods are urgently needed as sustainable alternatives to traditional cement-based solutions. In this study, industrial by-product fly ash and lime were utilized to stabilize saline soils, aiming to reduce environmental impact while enhancing frost resistance and durability. Unconfined compressive strength (UCS) tests, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and X-ray diffraction (XRD) were employed to assess both mechanical properties and microstructural evolution. The results indicate that lime-fly ash stabilization markedly increases UCS, with the highest improvement, approximately 34.2 times that of untreated soil, achieved using 20% fly ash after 28 days of curing. Freeze-thaw cycles (FTCs) induce microstructural changes, transforming larger inter-aggregate pores into smaller intra-aggregate pores (< 4 μm) and reducing the dominant pore size, leading to a denser soil matrix. The addition of fly ash enhances hydration reactions, forming calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) gels that improve the stability of soil under FTCs. Lime-fly ash stabilized soil exhibits greater strength retention and self-healing capabilities during FTCs compared to lime-stabilized soil. These findings provide insight into the long-term evolution of stabilized saline soils and offer practical implications for enhancing subgrade durability and environmental sustainability in cold-region infrastructure development.

Graphical Abstract

Salt crystallization is a major agent of deterioration in natural stones used in architectural and geotechnical applications. This study evaluated the resistance of four travertine types—Kütahya Red (KRT), Emirdağ Silver (EST), Antalya Noche (ANT), and Karaman Light (KLT)—to salt-induced weathering under controlled laboratory conditions. A comprehensive experimental program was implemented, including physical and mechanical characterization, chemical and mineralogical analyses (XRF, XRD), petrographic examination, and scanning electron microscopy (SEM). Salt crystallization tests were conducted over 15 cycles using Na₂SO₄·10 H₂O, MgSO₄·7 H₂O, NaCl, and KCl solutions. The results indicate that Na₂SO₄ produced the most severe deterioration, particularly in the EST and KLT samples, owing to the high crystallization pressures associated with phase transitions. MgSO₄ induced moderate damage, whereas NaCl and KCl caused limited surface alteration and internal degradation. ANT exhibited the highest resistance, retaining its mechanical strength, low porosity variation, and structural integrity across all salt exposures. In contrast, the EST and KLT experienced marked reductions in real density, ultrasonic velocity, and uniaxial compressive strength, along with increased water absorption and microcrack formation. Despite its initially dense structure, KRT displayed moderate susceptibility to sulfate salts. SEM analysis confirmed salt crystallization within the pore networks and the development of microcracks, particularly in the highly porous samples. These findings emphasize the influence of pore structure, mineralogy, and salt type on the durability of travertine. The results offer practical guidance for the selection and conservation of travertine stones in engineering and architectural settings that are exposed to saline environments.

The characteristics of Coarse Grained-Sliding Zone (CG-SZ) soil have a substantial impact on landslide deformation; nonetheless, studies examining its shear spatial deformation remain limited. At present, the correlation between the experimental results and the simulation results regarding CG-SZ soil is relatively weak. This study employs graphite core probes and performs particle image velocimetry (PIV) and discrete element method (DEM) to examine CG-SZ soil, which consists of spheroidal and blade particles with four levels of coarse particle contents. PIV observations reveal that for spheroidal particles, the shear band thickness varies with increasing coarse particle content, ranging from 13 mm to 18.1 mm. For blade particles, the shear band thickness changes with the rise in coarse particle content, ranging from 11 mm to 17.5 mm. The average shear band thickness of blade particle samples (43.12 mm) observed using graphite core probes is 17% greater than that of spheroidal particle samples. DEM analysis revealed that spheroidal particles exhibit a pronounced interlocking effect that leads to the formation of a stable coarse-grained skeleton structure, which in turn enhances the shear strength of spheroidal samples. Through energy analysis and the integration of experimental and simulation results, we classify the shearing process into four distinct stages: compaction, rapid damage, advantageous path development, and shear band penetration. The shear bands obtained using graphite core probes and PIV were analyzed, and the shear interface classified into main and secondary slip surfaces.

In-situ stress parameters are crucial for the design of construction support structures and disaster prevention in underground roadways. Lithology is a critical factor influencing the distribution characteristics of the in-situ stress field, which has not been thoroughly studied yet. To address the aforementioned issues, this study first establishes a computational mechanical model for the hydraulic fracturing method based on elastic mechanics. Subsequently, a self-designed small-aperture hydraulic fracturing in-situ stress test system is developed and applied in the western Guizhou mining area of China to measure in-situ stress measurements and investigate the lithology effects. Results indicate that a typical tectonic stress field, with the maximum horizontal stress as the major principal stress, characterizes the mining area. The in-situ stress values increase linearly with depth but exhibit discrete anomalies. The ratios of horizontal to vertical stress (K_Hv, K_hv, K_av) decrease with increasing depth and eventually stabilize toward specific values. Different rock masses’ maximum horizontal stress values increase with depth, but their growth gradients vary significantly, implying the in-situ stress field that is not controlled by a single factor. Additionally, the test system developed in this study provides new equipment and methodologies for in-situ stress measurements. Overall, the findings offer valuable data support for the design, construction, and support optimization of underground roadways in the western Guizhou mining area and similar regions.

Three-dimensional rough surface characterization was performed based on the Weierstrass-Mandelbrot (W-M) fractal function, investigating the impact of typical W-M geometric parameters on the morphology of the surface, and calculating the statistical parameters of the three-dimensional rough surfaces. The statistical parameters of the three-dimensional rough surfaces were calculated, the roughness characteristics of the fracture surfaces were quantified, and the relationship with the fractal dimension was established. A fracture seepage testing system was developed based on a self-designed structural surface and 3D engraving technology. Seepage tests were conducted on fractures with varying roughness levels. The results indicated that as the pressure gradient and roughness increased, the flow of the fluid exhibited pronounced non-linearity. The coefficients of the Forchheimer A and B equation increased with fracture roughness. Three-dimensional fracture samples exhibited overpressure drop phenomena as confining pressure increased. The surface roughness significantly influenced the non-linear fluid flow characteristics. As confining pressure increased, the flow resistance exhibited a non-linear relationship with the Reynolds number, indicating strong post-Darcy flow. As the pressure gradient gradually increased during the seepage process, the value of the non-linearity effect factor E increased, although the rate of increase slowed down over time. This study provides reliable analytical methods and models for studying fracture seepage characteristics.

The overlying soil layer exerts a significant impact on the seismic performance of pile foundations in liquefiable soil sites. In cold regions, the dynamic response of both the soil and pile foundation becomes intricate under the combined action of overlying frozen soil and liquefiable soil. This study employs an experimental method to investigate the seismic response of pile foundations in liquefiable soils with an overlying frozen soil layer. The analysis focuses on key parameters including pile strain, acceleration, and displacement of both the pile and surrounding soil, as well as pore water pressure in the sandy soil layer (liquefiable soil). During the test, liquefaction of the sandy soil layer initiates from the bottom and progresses upwards, and the liquefaction height increases as the ground motion intensity rises. The acceleration amplification coefficients of frozen soil and sandy soil are inversely correlated with the input ground motion intensity, indicating that the frozen soil can suppress the amplification of seismic waves. The peak horizontal displacement of the sandy soil layer is influenced by both the liquefaction height and soil elevation. Nevertheless, the impact of liquefaction on horizontal displacement is more pronounced than that of soil elevation. Moreover, the overlying frozen soil can enhance the bearing capacity of pile foundations in liquefied soil sites. Notably, abrupt strain changes are observed at the interface between frozen soil and sandy soil layers, as well as in the liquefied soil layer. These changes increase the vulnerability of pile foundations to seismic damage.

Glass fibers have recently been adopted as reinforcing materials to control compressibility and desiccation cracks in the landfill liner. Past studies have used fly ash as a suitable additive along with bentonite for landfill liner construction. In this study, waste glass fiber was used along with bentonite, fly ash, and their mixes to reinforce the liner material. The physico-chemical, microstructural, and mechanical performance of bentonite-fly ash and bentonite-sand mixes reinforced with glass fibers are investigated. A total of 225 unconfined compressive strength tests were conducted after 14 days curing period for each sample. A detailed analysis is carried out to understand the influence of glass fiber content on stress-strain response of bentonite-fly ash and bentonite-sand mixes. It is observed that, as the glass fiber content increases from 0.0% to 1.5%, there is an increase in unconfined compressive strength by about 213%. In all the cases considered, the bentonite-fly ash mixes resulted in a greater unconfined compressive strength than the bentonite-sand mixes. Based on the experimental data sets of B-FA mixtures, a new correlation between UCS and pH of the mixes was proposed. An increase in pH from 8.5 to 10.5 resulted in an increase of UCS by about 236% in glass fiber-reinforced mixtures.