Bulletin of Engineering Geology and the Environment最新文献

A fluid flowing through fractured rock masses has complex characteristics, and the fracture permeability of these rock masses is an essential parameter to evaluate the capacity of the fluid. In this work, five groups of fractured limestone samples with different joint roughness coefficient (JRC) were prepared using an innovative method. The effects of the JRC, filling fracture width (B_e), permeating solution, and confining and seepage pressures on the fracture permeability characteristics of limestone were investigated. The variation pattern of the fracture surface morphology was revealed, and the evolution of the fracture permeability of limestone was discussed. At constant confining and seepage pressures, the fracture permeability exhibited three distinct evolution stages with time: rapid decline, gradual decline, and stabilization. The stable value of the fracture permeability showed logarithmic and linear relationships with the JRC and B_e, respectively. Further, the results of permeability tests conducted on fractured limestone samples immersed in a sodium sulfate solution showed an increase in JRC from 2.50% to 36.61% for different fracture surfaces and a decrease in the sample permeability. The fracture permeability of the samples with different JRCs decreased with increasing pressure. There was a significant hysteresis effect during the unloading of the confining pressure. The loading and unloading of the seepage pressure reduced the fracture surface permeability at a confining pressure of 3.0 MPa and in the seepage pressure range of 0.2–1.5 MPa. This study provides a theoretical basis for estimating the fracture permeability of limestone and similar rocks.

As national energy demand increases, mining activities are extending deeper, raising concerns over the instability of anti-dip slopes. NPR anchor cables, known for high strength and ductility, address the limitations of traditional cables and are more suitable for deep slope support. Using the slope failure at the Changshanhao Gold Mine as a reference, based on the similarity ratio theory, we conducted model tests using the “Engineering Disaster Model Testing System” to compare disaster prevention effect between 2G-NPR and traditional anchor cables. The experimental results indicate that 2G-NPR cable can effectively redistribute external loads, achieving a stable constant resistance of approximately 35.2 N and demonstrating excellent adaptability under complex conditions. A thorough analysis was conducted on the stress-strain, temperature, and displacement fields throughout the slope failure process. The evolution of the monitoring data was summarized, and the failure patterns under 2G-NPR and traditional anchor cable support were compared. The study revealed the failure mechanism of anti-dip slopes and the working principles of the 2G-NPR cable in landslide control. A comprehensive evaluation of the application effectiveness of 2G-NPR anchor cables in landslide hazard mitigation was conducted, providing insights and guidance for the use of NPR anchor cables in anti-dip slope control projects.

Expansive soils, characterized by significant volume changes in response to moisture fluctuations, present substantial engineering challenges globally. This study explores the efficacy of lignosulfonate (LS), an industrial by-product, as a sustainable stabilizer for expansive soils. Three soil samples with varying degrees of expansiveness (weak, mid, and strong) were treated with LS, and their geotechnical properties were evaluated. For weak, mid, and strong expansive soil, the optimum lignosulphonate content (OLS) determined based on the free swelling rate and plasticity index was 0.75%, 2%, and 6%, respectively. The addition of LS resulted in a reduction of the liquid limit, plasticity index, and free swell index across all soil types. Furthermore, LS-treated soils exhibited enhanced resistance to volume changes and improved shear strength under cyclic wet-dry conditions. Moreover, crack development is inhibited in LS-modified soil. LS decreases the soil’s affinity for water by creating a hydrophobic barrier around soil particles. Furthermore, the interaction between LS and the layered clay minerals results in stronger binding, which contributes to the stabilization process. The findings indicate that LS not only reduces the swelling nature of expansive soils and improves their shear strength and stability under wet and dry cycling conditions, but also provides an environmentally friendly solution for soil stabilization and sustainable construction practices.

Although the root can enhance the soil's strength, vegetation cover landslide still occurs frequently under the rainfall. To elucidate the mechanism underlying the degradation of the shear strength of root‒soil composites under the influence of moisture, we investigated trees from hilly slopes in southeastern China. The tensile mechanical properties of roots were tested under varying moisture conditions.The results of previous work on the friction characteristics of the root-soil interface under different soil water content were also considered. Furthermore, large-scale direct shear tests were performed to assess the strength characteristics of root-soil composites under different root cross-sectional area ratios (RAR) and moisture contents. Based on the widely used Wu model, and incorporating the failure modes of roots in root‒soil composites and the mechanism of root‒soil interface friction, a root‒soil composite strength degradation model was established considering the effects of moisture. Moisture significantly affected the tensile strength of fine tree roots, with the tensile strength of fine roots being lower in the saturated state than in the fresh state. In contrast, coarse roots were almost unaffected by moisture. As the moisture content increased, the additional strength provided by the roots decreased, and the root efficiency (RE_p) decreased significantly. The model was validated against experimental data, and the calculated results were accurate. In root‒soil composites, as moisture infiltrates, the tensile strength of the roots, soil shear strength, and root‒soil interface shear strength decrease to different degrees. This results in reduced resistance to deformation in the root‒soil composites, leading to a decrease in its strength.

Traditional landslide susceptibility mapping (LSM) typically employs a point sampling approach, which may neglect the variability of spatial data and the selection of evaluation units, thereby introducing uncertainty into landslide susceptibility predictions. Specifically, when compared to the actual boundary shapes of landslides, simple spatial locations are inadequate for capturing the full spectrum of complex information present in the geological environment, and the correlation between grid units and real-world terrain conditions is not sufficiently close. Addressing these issues, this study focuses on Yongji County as a case study and the spatial coordinates and morphological boundaries of landslides served as input variables for the spatial data, with CatBoost (CB) and Random Forest (RF) algorithms employed for training the predictive models. Subsequently, grid units, slope units and topographic units were selected as mapping units. Ultimately, this study employs analytical techniques such as the Receiver Operating Characteristic (ROC) curve and the analysis of Landslide Susceptibility Indexes (LSI) distributions to assess detailed quantification of uncertainty and precision that results from the selection of spatial datasets and evaluation units. The results indicate that utilizing landslide boundary shapes with higher reliability and precision as input variables significantly enhances the overall accuracy of LSM predictions compared to those based on spatial positions, concurrently diminishing the uncertainty associated with the predictive outcomes; across diverse scenarios, the model that combines slope units with landslide boundary shapes achieves the highest precision.

Understanding the rockburst behavior of layered rocks is of great significance for ensuring the safety of underground engineering and optimizing design and construction. To explore the influence of bedding angle on the rockburst behavior, uniaxial compression tests with single unloading were conducted on layered sandstone, separating elastic energy and dissipated energy by unloading and obtaining energy distribution characteristics at different loading stages. The laboratory results indicate that the distribution relationship between elastic and dissipated energy follows the linear energy storage and dissipation (LESD) law. As the bedding angle increases from 0 to 90°, the elastic energy conversion coefficient varies from 0.7296 to 0.7722, and peak elastic energy decreases from 295.74 mJ/cm³ to 201.24 mJ/cm³, indicating that the bedding angle has little effect on the elastic energy conversion capacity but has a significant weakening effect on the peak energy storage capacity (mainly concentrated between 22.5° and 67.5°). Based on the LESD law, three energy-related indexes were calculated to evaluate rockburst proneness. Compared with the rockburst proneness index related to elastic energy conversion ability, the index related to peak energy storage capacity can better distinguish the influence of bedding angle on rockburst proneness, the rockburst proneness is greater between 0° and 22.5°. This study can help to better understand the influence of bedding angle on rockburst behavior from an energy perspective.

This study looked at the effectiveness of liquid nitrogen (LN₂) in two distinct coal fracturing processes, freezing time (FT) and freezing–thawing cycle (FTC), for specimens that were saturated with water. The effectiveness of cryogenic treatment for coal rocks was compared using uniaxial compressive strength (UCS) and Brazilian tests. The results indicated in both USC and Brazilian tests, FTC experiments showed better results compared to FT experiments, leading to the conclusion that it may be possible to attain a higher desired permeability improvement by using more LN₂ injections in real-world LN₂ fracturing applications. In brittleness analysis, FT experiments showed higher values than FTC in the B21, B22, B24, and B25 indexes, while FTC experiments showed higher values in the B19 and B20 indexes. A scanning electron microscope (SEM) was used for fracture evolution analysis. Further, numerical simulations detailed the stress distribution patterns within coal samples under cryogenic treatment, utilizing von Mises stress analysis to compare the progression over time. The simulation results, particularly at peak stress periods, strongly correlate with experimental data, validating the model's effectiveness. These findings offer substantial evidence for the feasibility of LN₂-based treatments in enhancing coal bed permeability, with implications for improving the efficiency and safety of coal extraction processes.

Microbial-induced calcite precipitation (MICP) is an environmentally friendly treatment method for soil improvement. When combined with carbon fiber (CF), MICP can enhance the liquefaction resistance of sand. In this study, the effects of CF content (relative to the sand weight of 0%, 0.2%, 0.3%, and 0.4%) on the liquefaction resistance of MICP-treated silica and calcareous sand were investigated. The analysis was conducted using bacterial retention test, cyclic triaxial (CTX) test, LCD optical microscope, and scanning electron microscopy (SEM). The results showed that with the increase in CF content, the bacterial retention rate increased. Additionally, the cumulative cycles of axial strain to 5%, excess pore water pressure to initial liquefaction, as well as strength and stiffness, all increased with higher CF content. This trend continued up to the CF content of 0.2% for silica sand and 0.3% for calcareous sand, beyond which the cumulative cycles began to decrease. The great mechanical system of CF, calcite, and sand particles was significantly strengthened after MICP-treated. However, the reinforced calcite did not completely cover the CF, and excess CF hindered the connection between sand grains. The optimal amount of CF in silica and calcareous sands were 0.2% and 0.3%. This study provides valuable guidance for selecting the optimal CF content in the future MICP soil engineering.

China, a mountainous country with developed seismic fault zones, frequently experiences landslides triggered by earthquakes, so it is crucial adjective to explore the movement characteristics of landslides caused by earthquake. Utilizing the Daguangbao landslide as a case study, this paper analyzes movement characteristics of landslide under earthquake magnitude and duration time by means of numerical simulation and control variable methods. Firstly, the original topographic conditions and earthquake magnitude of Daguangbao landslide are restored, and its displacement movement characteristics is studied. Secondly, the landslide movement characteristics under different earthquake magnitudes (VI, VIII, VIII, IX) and duration time (10 s, 20 s, 30 s, 40 s, 50 s, 60 s) are obtained through 27 displacement monitoring points on three sections. Finally, the displacement–time formulas of Daguangbao landslide with different earthquake magnitudes are obtained by linear and nonlinear fitting. The research results show that: (i) The formation process of Daguangbao landslide can be summarized into the following four stages: Stage of earthquake wave shatters slope body; Stage of the formation of main sliding surface; Stage of the sliding of main sliding body; Stage of the sliding accumulation. (ii) In the case of earthquake magnitudes VI, VII and VIII, the landslide displacement increases linearly with the earthquake duration time. (iii) In the case of earthquake IX, the landslide displacement increases first and then decreases with the increase of earthquake duration time. The research reveals the mechanical mechanism of landslide under earthquake action, which provides reference and guidance for the study of the motion characteristics of earthquake landslides, and provides a basis for landslide control and disaster prevention and reduction.

The variation in soil moisture can lead to unfavourable deformation of highway embankments, threatening their long-term stability under seasonal groundwater level fluctuations and frequent changes in evaporation and precipitation. This paper conducted unsaturated soil triaxial tests to examine soil water retention and volumetric deformation behavior during wetting–drying cycles. The results show that soil water retention decreases with increasing wetting–drying cycles, particularly in the low suction range from 0 to 100 kPa, where gravimetric moisture content (GMC) declines sharply. With more wetting–drying cycles, the soil’s capacity for volumetric deformation diminishes. The soil has a loose soil structure and is more prone to plastic deformation. Furthermore, three soil water retention models, the Gallipoli, Tarantino, and Hu models were employed to analyse soil’s hydromechanical behaviours and evaluate the effect of wetting–drying cycles. It was found that Tarantino’s model used only three fitting parameters, which were more concise and maintained a good fitting effect. This study clarifies soil–water retention and volumetric deformation behavior during wetting–drying cycles, which is essential for effective water control in subgrade construction and operation.