Bulletin of Engineering Geology and the Environment最新文献

Accurate identification of discontinuities is essential for rock mass stability analysis. With the development of remote sensing technologies, non-contact measurement has become a mainstream approach. In this regard, this paper presents a new method to identify rock discontinuities from 3D point clouds that balances accuracy and efficiency. The proposed method first applies the k-nearest neighbor (KNN) search algorithm and principal component analysis (PCA) to calculate the normal vectors. Based on the calculated roughness values, edge and sharp regions are discarded. Clustering seed points are generated by uniform downsampling method, and the multipoint clustering algorithm (MPC) is developed to recognize individual discontinuities from the point clouds. The random sample consensus (RANSAC) algorithm is applied to determine the orientation of the discontinuities, and an improved self-organizing map (SOM) neural network is used to group the discontinuity sets. Finally, the performance of the new method is evaluated via three real-world cases. The research results demonstrate that the proposed method can accurately identify discontinuities from outcrop rock mass, with the error being within 3° compared to manual measurement. Moreover, the computational efficiency of the new method is several times faster than that of previous research methods. The new method can be used to recognize rock discontinuities from large-scale 3D point clouds.

Calcareous sand serves as a critical construction material for infrastructure development in the South China Sea region. Despite extensive macroscopic research, understanding of micro-scale failure mechanisms under complex loading conditions remains limited due to challenges in sample preparation and testing apparatus limitations. This study introduces a novel experimental methodology to investigate the micromechanical behaviour of artificially cemented calcareous sand particles under compression, combined compression-shear, and compression-shear-bending conditions using a custom-designed particle mould and specialized loading apparatus. Compression tests revealed three distinct failure modes (vertical cracks, inclined cracks, and combined patterns), with samples exhibiting vertical and combined fractures demonstrating higher peak resistance. The particle-bond interface morphology significantly influenced the strength characteristics. Critical cracks predominantly initiated at particle-cement interfaces with propagation velocities of 50–60 mm/s. In shear tests, failure occurred through either particle-bond interface debonding or bond fracture, with local contact geometry inversely affecting shear resistance. During bending tests, normal force emerged as a governing parameter significantly influencing mechanical response, while increasing eccentricity shifted the dominant failure mechanism from shear-controlled to bending-controlled. This research provides new insights into the micromechanical behaviour of cemented calcareous sands, establishing critical reference data for computational modelling and advancing understanding of cemented granular materials from micro to macro scales.

Roof sandstone fissure water poses a significant threat to mine safety due to its concealed occurrence, discontinuous distribution, and poor drainage efficiency under traditional borehole pre-drainage methods. To address this challenge, this study analyzes the types and mechanisms of roof sandstone fissure water hazards and proposes a pulse hydraulic fracturing-assisted pre-drainage method for constructing artificial water-conducting channels. By installing drainage boreholes and applying high-frequency pulsed water-pressure, PHF generates dense, multi-directional fracture networks within the sandstone fissure aquifer, effectively connecting previously discontinuous water-bearing zones. This approach efficiently drains water from roof fissures into boreholes, significantly extending the effective drainage radius of a single borehole. Field tests conducted at the Ⅲ412 working face of Hengyuan Coal Mine demonstrated periodic water pressure fluctuations (15–33 MPa), with dense axial and circumferential fracture networks formed on borehole walls and fracture propagation distances of 15–30 m. The variation curve of the water outflow rate from the boreholes after pulse hydraulic fracturing is divided into a sharp increase stage, an attenuation stage, and a stable stage. The maximum water outflow rate of a single borehole is 5 m³/h. The maximum volume of water spared from a single borehole within 72 h was 226.12 m³. Variations in drainage volume before and after fracturing effectively characterized the water abundance features of the regional aquifer. This technology offers technical and economic advantages for the efficient drainage of water from the sandstone aquifer and also serves as a tool for mine pressure management.

The brittleness of rocks significantly impacts the rock-breaking machinery and tunnel excavatability. By considering the energy conversion mechanisms, a new rock brittleness index (BI_N) to evaluate tunnel boring machine (TBM) tunneling efficiency is proposed in this study. With the Longyan Wan’anxi diversion tunnel as an example, the proposed index is used to study the differences in brittleness of granite and sandstone and the effects of moisture conditions, and the relationships between BI_N and TBM are analyzed as well. The results indicate that the proposed index can be used to characterize rock brittleness effectively. Greater rock strength and lower mechanical energy result in increased surface area of rock chips per unit volume after breaking (i.e., greater brittleness), and brittleness decreases with the increase of moisture content. Granite generally exhibits greater brittleness than sandstone, while sandstone shows more significant negative correlation between brittleness and moisture content. Specifically, the BI_N of granite and sandstone had decreases of 32.86% and 42.11% respectively after saturation. Besides, comparative analysis of other brittleness indices reveals a good correlation between the proposed brittleness index and TBM specific energy (SE). Furthermore, the relationship between BI_N and Cerchar Abrasivity Index (CAI) for the two types of rocks under dry and saturated conditions was explored respectively. For sandstone, a linear relationship between BIN and CAI is observed regardless of being in a dry or saturated state.

There is a lack of multi-scale analysis of railway slope deformation and quantitative analysis of the correlation between rainfall features and railway slope deformation. Consequently, this research develops a comprehensive analysis method of rainfall-deformation characteristics for railway slopes and performs a case study. Firstly, the macro-deformation characteristics of the target area and slope are analyzed using the unmanned aerial vehicle (UAV) and field survey. Secondly, the multi-scale deformation characteristics of the railway line, target area, and target slope are analyzed using interferometric synthetic aperture radar (InSAR) technology and multiple noise reduction and machine learning algorithms. Finally, the deformation-rainfall correlations are quantitatively analyzed in months and years. Moreover, we analyze the hydrological characteristics of the target slope and the possible causes of instability in the discussion. The results indicate that the deformation rate of about 80% of the area along the railway line ranges from − 42.795 to 0.000 mm/year, and the deformation in the target area is non-uniform in spatio-temporal scales. The time-series deformation of the target slope increases sharply during the months of instability. The ordering of the comprehensive metric for correlation analysis (CMCA) values is Five-day rainfall (15) > Four-day rainfall (12) > Three-day rainfall (7) = Two-day rainfall (7) > Rainfall intensity (4), which indicates that railway slope deformation is not only related to the rainfall intensity, but also to cumulative rainfall. The causes of the case slope could be summarized as the saturation stage, the disintegration and cracking stage, the deformation development stage, and the instability and destruction stage.

Coral sand is extensively distributed across the islands and reefs of the South China Sea, whereas its inherent brittleness and high crushability present substantial engineering challenges. This study examined the enhancement of coral sand through reinforcement with recycled tyre strips, aiming to achieve both mechanical improvement and sustainable waste utilization. A series of triaxial shear tests were performed to explore the effects of relative density, confining pressure, and reinforcement layering on shear strength, dilatancy, and particle breakage behavior. The results indicated that reinforcement reduced particle crushing by 10.78–46.26% and lowered the relative breakage index through stress redistribution at the sand-strip interface. The peak shear strength increased by 22–52%, particularly under low-density and low-confining-pressure conditions, while volumetric strains were stabilized and the critical void ratio was reduced. The critical state line shifted upward, reflecting higher critical stress ratios and sustained shear resistance under elevated effective stresses. However, stress concentration at the sand-strip interface intensified particle breakage under high confining pressures, leading to a reduction in the peak friction angle. The multilayer reinforcement progressively enhanced strength parameters, whereas with diminishing returns, as the strength benefit ratio decreased from 1.4 to 1.32 with increasing reinforcement layers. High-density coral sand demonstrated a relatively limited improvement owing to inherent particle interlocking. Recycled tyre strips improved interfacial toughness, redistributed stress transmission, and preserved particle integrity, thereby providing an optimized framework for coral sand reinforcement in coastal infrastructure and achieving a balance between mechanical performance and environmental sustainability.

Biopolymers have received research attention for improving the erosion resistance and strength of coarse-grained soils. Unlike cement-treated soils, however, no standardized tests have been developed to assess the durability of biopolymer-treated soils under cyclic drying and wetting conditions. Therefore, questions remain on their long-term stability. The main goal of this study is to examine the performance of biopolymer-treated sandy soils both over time and with cyclic drying and wetting. This work focuses on Xanthan Gum (XG) as a model biopolymer for treating sandy soils. Compacted biopolymer-treated specimens were subjected to cyclic drying/wetting according to the ASTM code designed for soil-cement mixtures. The specimens were dissected after each cycle to study the mechanism and progression of failure. Furthermore, the biopolymer pore fluid was extracted and studied using rheology and infrared spectroscopy (FTIR) to investigate the effects of drying and wetting on the physical and chemical properties of the biopolymer gel. It was found that the low hydraulic conductivity of the biopolymer-treated sand creates a unique distribution of moisture in the compacted specimens. Rheological investigations indicated a reduction in the yield stress of the pore fluid in the “crust” of the specimens, which played the main role in the failure of the specimens under cyclic drying and wetting. FTIR tests showed evidence of biological degradation of the biopolymer. Cyclic drying and wetting tests were also performed on pure biopolymer gels to further investigate the degradation of biopolymers independent of the soil.

Landslides with deep-seated clay-rich shear zones are highly susceptible to intense rainfall infiltration. Such hydrological disturbances promote pore-pressure generation within the shear zone, reducing effective stress and potentially triggering unexpected sliding. This study investigates a rainfall-induced catastrophic landslide in the Three Gorges Reservoir area through laboratory tests and numerical simulations. A series of direct shear tests were conducted under constant shear stress paths, where increased back pressure was applied to induce pore pressure and trigger instability. The results show that the shear-zone soils are prone to instability under hydrological perturbations, with the response strongly influenced by mobilised stress levels. Numerical simulations, based on a hypoplastic model calibrated with test data, further reveal that crack infiltration accelerates saturation, promotes the development of a continuous basal sliding surface. The close agreement with field evidence confirms that pore-pressure buildup is the primary driver of rainfall-induced landslide initiation and underscores the critical role of crack infiltration in accelerating failure.

The eastern margin of Tibetan Plateau is the area of the most active and intense internal and external dynamic action in Chinese mainland, where large unstable slopes are well developed. This type of slope instability is prone to form a complex landslide disaster chain. Through field investigations, SBAS-InSAR, and numerical simulations, failure characteristics, deformation monitoring and landslide-barrier lake-outburst flood disaster chain initiated by slope failure were studied. The results show that the steep topography of the slope provides favorable free-face condition for slope possible instability. Under the influence of faults, freeze-thaw cycles, the deformation and failure phenomena of the slope are obvious. During the monitoring period, the most intense deformation areas are located at the leading edge of the slope. The maximum annual mean deformation rate and maximum cumulative deformation value were 60 mm/yr and 320 mm, respectively. Landslides are most likely in the upper and middle slope areas. Landslide will take approximately 70 s from start-up to the formation of the barrier dam. A barrier lake with a maximum dam height of 110 m and a storage capacity of 1.16 × 10⁹ m³ can be formed. After the dam-break flood occurred, the maximum depth of the outburst floods at the site of the downstream Yigong Zangbu Bridge could reach 18 m. In light of these findings, strengthening multi-source collaborative monitoring (satellite, aerial, ground, and subsurface) in the study area and formulating targeted “four precaution” measures are recommended.

Soil liquefaction remains a significant threat to infrastructure built on saturated silty deposits. To evaluate its key influencing factors, this study investigates the effects of clay content (CC), fines content (FC) and intergranular void ratio (e_i) on the liquefaction resistance of saturated silty soil. A series of undrained cyclic triaxial tests were conducted on reconstituted specimens with varying CC and FC. The results indicate that the cyclic resistance ratio (CRR) does not correlate well with fines or clay content alone. To quantitatively assess liquefaction resistance, the concept of the intergranular void ratio of silty soil is introduced, which better reflects the active soil skeleton state from a microstructural perspective by considering particle contact mechanisms. Analysis of the experimental data reveals a negative power-law relationship between e_i and CRR. For specimens with CC ≤ 8%, this relationship is quantified as CRR = 0.362·(:{e}_{i}^{-0.771})with R² = 0.94. This study establishes e_i as a superior state parameter and provides a new perspective on evaluating the liquefaction potential of silty soil by linking microstructural parameters to macro-scale behavior.