Bulletin of Engineering Geology and the Environment最新文献

True triaxial hydraulic fracturing experiments with acoustic emission (AE) monitoring were conducted on raw shale samples to investigate the damage behavior of induced fracture. By varying the injection rate, the study analyzed the morphology and the propagation process of induced fractures in shale under different burial depth. Based on the fractal characteristics of AE parameters, an induced fracture damage evolution model was developed. Results indicate that the number of shear cracks rose substantially in conjunction with elevated in-situ stress as the injection rate increased. The induced fracture damage evolution demonstrated three growth patterns: S-shaped, concave, and nearly linear. AE energy exhibited self-similarity in the time domain, the fractal dimension showed an evolutionary trend of “decreasing→fluctuating→stable”. The valley value in the fractal dimension signified the major crack initiation, while the stable state indicated the formation of the final crack network as fracture surfaces penetrate. Furthermore, a correlation model linking fractal dimension with injection rate and in-situ stress was established. This research provides an integrated insight into understanding the damage process and predicting the complexity of hydraulic fracture networks.

To investigate the mining pressure behavior of gob-side roadways influenced by fault tectonic zones, the Xinjulong Coal Mine is taken as the engineering background. The initial stress distribution and the effects of fault parameters on stress evolution were analyzed through theoretical analysis. Numerical simulation and three-dimensional model tests were then conducted to examine the stress and displacement evolution of the gob-side roadway and overlying strata. The results show an asymmetric stress distribution near the fault, with the hanging wall bearing higher stress than the footwall. The gob-side roadway is simultaneously affected by the abutment pressure of the adjacent gob and the fault-induced tectonic stress. During roadway excavation and working face mining, the maximum stress in the coal pillar of the gob-side roadway is 1.8 times that in the non-gob-side roadway. The height of the collapsed arch is approximately 36 m, with a collapse step distance of 40 m. Under the combined influence of the adjacent gob, fault tectonic, and mining-induced abutment pressure, the stress concentration is significant. The hanging wall of the fault and the coal pillar together constitute a high static stress zone, where substantial elastic strain energy is accumulated. Meanwhile, the abrupt collapse of a hard roof exerts intense dynamic disturbances on the gob-side roadway already subjected to high stress, thereby creating the inducing condition for rockburst under the coupled effect of high static and strong dynamic loads.

Dispersive soil has strong dispersibility and low erosion resistance in water. Biological and chemical modification offers an environmentally friendly soil improvement method. This study investigates the effects of biopolymer xanthan gum (XG) and water glass (WG) on the and properties of dispersive soil. Specimens containing 5% WG with varying XG content (0.1–0.5% for dispersivity assessment; 1–5% for mechanical testing) were prepared and cured for 28 days. Dispersivity and water stability were evaluated through pinhole tests, cube sample crumb tests, and remoulded sphere sample crumb tests. Mechanical properties were assessed via Brazilian tensile strength, unconfined compressive strength, and direct shear strength tests. Chemical (pH), mineral and microstructural changes were systematically analyzed. Additionally, modification mechanisms of different modification materials for dispersive soils were compared. The long-term strength was predicted using the Generalized GM(1,1) power model and Particle Swarm Optimization algorithm. Results show that when the XG content reaches 0.4% and 0.5%, the soil can transform from strong dispersibility to non-dispersibility. WG and XG can significantly improve the mechanical properties. When the XG content is 5%, BTS is increased by 288%, while the internal friction angle shows a trend of first slightly increasing and then decreasing. There is a significant negative correlation between pH and mechanical strength, with a 12.6% decrease at 5% XG content. Prediction results and mechanism comparison confirm that XG + WG is a long-efficiency and low-impact biochemical composite modifier. This study provides an efficient solution to address a series of disaster issues caused by dispersive soil.

During the construction process of blocky rock mass tunnels, the phenomenon of falling arch blocks frequently occurs. To truly reflect the deformation characteristics of the surrounding rock, an interlocking structure block model method considering the distribution characteristics of the surrounding rock structural planes was proposed, and the rationality of the structured block model was validated through numerical calculations. First, by conducting an interlocking structured block model test, the deformation and failure characteristics of the tunnel section during the excavation process were analyzed, and the displacement of the surrounding rock clearly exhibited asymmetrical deformation. Owing to the interlocking effect of nonpenetrating blocks, the torsion and subsequent gyration of the blocks limited the range of surface damage to the surrounding rock, ultimately resulting in shear fracture during the overload test. Second, compared with the phenomenon of small deformation of the surrounding rock in the continuous medium model, whose bearing capacity is 9 times that of geostress, the nonpenetrating structural plane inlaying structure block model formed a pressure arch structure with a height of one quarter of the tunnel diameter, resulting in a bearing capacity that is twice as high as the geostress, which is closer to the actual engineering situation. In addition, the prestressed rock bolt support technology effectively controlled the deformation of the surrounding rock of the block test model, and the deformation of the surrounding rock was controlled at 6.5 mm through field testing. The block test model accurately reflects the variation characteristics of jointed surrounding rock and provides a reference for tunnel support design.

Calcareous sand has been widely utilized as the primary hydraulic filling material in offshore engineering projects. A thorough understanding of its mechanical properties is crucial for ensuring the long-term stability of offshore structures. Calcareous sand foundations are prone to excessive deformation and particle crushing due to their inherently fragile characteristics. Geotextile reinforcement has gained attention as an effective method for enhancing the overall strength and stability of geo-structure in marine environments. This study examines the influence of geotextile arrangement type on the mechanical behavior of calcareous sand through a series of drained triaxial shear tests. The experimental results demonstrate that the incorporation of geotextile layers significantly enhances the mechanical performance of calcareous sand specimens. An increasing number of geotextile layers leads to improvement of peak shear strength and delays the axial strain corresponding to the failure state, while reducing post-peak strength degradation tendency. Furthermore, both the apparent cohesion and friction angle of the calcareous sand increase with the geotextile layers. The addition of geotextile layers effectively suppresses dilation behavior and significantly constrains lateral deformation, resulting in a transition in the failure mode from shear band formation to bulging between adjacent geotextile layers. The presence and number of geotextile layers has a significant influence on the mechanical properties of geotextile-reinforced calcareous sand at the critical state.

This study investigates the transition in rate-dependent shear response of rock-like joints due to clay-infill. The model material was used to prepare discontinuity samples, and Kaolin clay was used as the infill. A total of 64 direct shear tests were performed on prepared samples with varying displacement rates (0.05-40 mm/min), normal stress (0.5-4 MPa), and infill thicknesses (t/a = 0.5 to t/a = 1.5). The effect on strength, dilation, and joint surface roughness under different shearing conditions is investigated. The changes in joint roughness profile post-shearing are quantified via a 3D laser scanner, with its data processed via the Delaunay triangulation algorithm implemented in MATLAB. The quantified changes in roughness are used to understand the possible micro-mechanisms during joint shearing. The unfilled joints exhibited velocity-strengthening behaviour, i.e., strength increases with rate, with its extent depending upon the normal stress. A transition in the rate-dependent nature of the joints, i.e., velocity strengthening to velocity-weakening, was noticed with the introduction of the infill. The rate-dependency of infilled joints showed minimal dependence on the normal stress and the infill thickness. The volumetric behaviour of both unfilled and infilled joints was rate-dependent. The unfilled joints were, in general, dilatative in nature, with higher dilation observed at low rates and low normal stress. The infilled joints exhibited a compressive nature in general, with higher compression observed at low rates and high infill thickness. Further, the stick-slip behaviour was exhibited by both unfilled and infilled joints at lower rates, with high-amplitude events observed for unfilled joints. These observations were validated and explained via detailed roughness analyses.

During the blasting excavation of rock slopes, the presence of complex joint and fracture networks, coupled with strong multifactorial disturbances, leads to highly nonlinear and unpredictable damage evolution and instability mechanisms. Traditional stability analyses, relying on limit equilibrium theory, numerical modeling, or single-parameter approaches, often fail to capture the coupled effects of multiple blasting parameters and the complete damage evolution under dynamic loading conditions. To address these limitations, this study proposes an innovative three-dimensional DFN–PFC-based slope stability analysis method that integrates discrete fracture network (DFN)–based damage quantification with response surface methodology (RSM) for multi-parameter optimization. By conducting batch numerical simulations and automated data extraction, the coupled effects of key variables—including charge quantity, initial damage, disturbance distance, and lithological strength—on slope failure were quantitatively analyzed. The results indicate that increased coupling between charge quantity and damage levels significantly reduces the safety factor, thereby increasing the risk of instability; in contrast, greater disturbance distances or lower joint densities contribute to enhanced slope stability. The safety factor prediction model developed in this study, based on RSM, effectively quantifies the combined influence of multiple parameters and provides a scientific basis for optimized blasting design and risk control in complex jointed rock slopes.

Despite the significant advantages of using aeolian sand as fill material in desert road and railway projects, concerns persist regarding its inferior mechanical properties potentially compromising structural safety. For elucidating its mechanical behavior, a series of monotonic and cyclic triaxial tests were conducted on saturated and dry aeolian sands from Taklamakan Desert under different confining pressures and relative densities. The shear strength, deformation and critical state characteristics in monotonic tests, as well as the accumulated axial and volumetric strains in cyclic tests were analyzed. The test results showed that compared to saturated aeolian sand, dry aeolian sand exhibited larger shear strength and dilation in monotonic tests, while in cyclic tests it showed smaller accumulated axial strain. The critical states of saturated and dry aeolian sand were different, with the critical state stress ratio and void ratio of the dry specimen being larger than those of the saturated one. These phenomena indicated that determining the strength and deformation of dry aeolian sand in practical engineering through conventional saturated specimens was conservative. Furthermore, as relative density increased, aeolian sand exhibited significantly enhanced strength and reduced cyclic accumulated strain. The strength and deformation of aeolian sand could meet engineering requirements when adequate compaction was achieved.

Near-fault ground motion, with short-duration, high-energy and strong pulse characteristics, is more destructive than far-field ground motion and more likely to induce complex failure modes of jointed slopes. Natural slope surfaces typically exhibit irregular shapes with significant concave convex characteristics, whose specific geometry causes slope stability to vary remarkably. Therefore, the dynamic stability of near-fault jointed slopes needs further study based on the pulse-like ground motion and concave convex characteristics. This study constructs up rotation-lower translation and up translation-lower rotation models for irregular geometric slopes with n polyline segments, incorporating concave convex characteristics and failure modes. This study derives the factor of safety (Fs) and permanent displacement expressions under each failure mode, and analyzes parameter impacts (particularly pulse-like ground motion and concave convex characteristics) using real landslide data. Studies have shown that when the pulse-like ground motion is considered, the permanent displacement of the slope can be 19 times greater than that without considering it. When the concave-convex characteristics are considered, the variation in Fs can reach 16.9%. In the case of the Ganmofang landslide (China), this study’s Fs = 1.186 has a 3.025% error from numerical simulation 1.223. In the near-fault region, the peak ground acceleration (PGA) is generally greater with a_max = 0.8 g, and the permanent displacement reaches 235.32 cm. This study reveals that slopes under strong pulse-like ground motion with short-duration and high-energy characteristics, using permanent displacement for evaluation is more appropriate and reliable.

In the summer of 2022, a devastating wildfire struck the Bohemian Switzerland National Park in Czechia. It not only had significant ecological and economic impacts but also altered the near-surface properties of the vastly exposed quartzose sandstones of Upper Cretaceous age. This, together with the loss of vegetation and altered composition of slope sediments, may influence the dynamics of sandstone rock pillars and increase their vulnerability to erosion and slope processes in the coming years. This work focuses on describing the rock material affected by the 2022 wildfire, investigating the effects of thermal shock and extreme heat under natural conditions. The research employs a multi-step framework encompassing in situ sampling, laboratory tests and GIS modelling to understand these changes and patterns comprehensively. Samples were collected from outcrops and free-lying blocks at three locations: Dlouhý, Pravčický, and Černý důl. A total of 37 drill cores were extracted, with 185 P-wave velocity measurements conducted to assess variations with depth. Additionally, 78 samples were prepared for Unconfined Compression Tests and Brazilian tensile strength tests, complemented by 156 P- and S-wave velocity measurements. Notably, the Brazilian specimens yielded more pronounced results, revealing significant differences in tensile strength between Dlouhý and Černý důl at varying depths. Given the perspective of recurring monitoring in protected areas such as the study site, the research applied ultrasonic methods to offer a practical tool for assessing post-fire rock quality while adhering to standard laboratory tests. Clear limitations in the heterogeneous material were identified, with values showing limited amplitude in rock strength decay. This work provides a peculiar case study offering insights into changes in the properties of rock materials in the presence of a major wildfire.