Bulletin of Engineering Geology and the Environment最新文献

Graphitic carbon nitride (g-C₃N₄) was synthesised by thermal polycondensation of melamine and subsequently exfoliated by calcination at 600 °C for 30, 45, and 60 min. The resulting nanoparticles—differing in morphology, size, and specific surface area—were dispersed in a poly(alkyl siloxane) hydrophobising agent at concentrations of 2 g·L⁻¹ and 4 g·L⁻¹ and applied to the surface of porous quartz sandstone. The effect of the degree of g-C₃N₄ exfoliation on the self-cleaning performance of the resulting coatings and their interaction with water was evaluated. Photodegradation tests performed on sandstone samples artificially stained with Rhodamine B confirmed a self-cleaning effect for coatings containing particles exfoliated for 45 and 60 min, at a concentration of 4 g of g-C₃N₄ per litre of poly(alkyl siloxane). The addition of nano-g-C₃N₄ enhanced the hydrophobicity of the sandstone surface. The coatings substantially reduced water uptake into the stone’s pore system while still allowing water vapour to evaporate freely into the surrounding environment. g-C₃N₄ thus appears to be a promising photocatalytically active nanomaterial for self-cleaning and water-repellent surface protection of building and sculptural stone—a field in which it has not yet been applied.

Slopes are considered porous media in rainfall infiltration analysis based on two-phase flow model, while the impact of preferential flow through internal fractures is typically overlooked. This study aims to investigate water and air transport patterns within fractures during rainfall and their impact on the stability evolution. In this paper, a novel framework is developed to couple two-phase flow with the stability analysis of fractured rock slopes. Firstly, a hydromechanical coupled model is proposed and verified to simulate water‒air interactions. Secondly, two original FISH functions are proposed to implement a more physically representative relative permeability model and a more realistic boundary condition for simulating rainfall infiltration under two-phase flow model. Further, the failure modes with different fracture distribution characteristics are revealed using the Universal Distinct Element Code. Finally, the applicability of the proposed model is demonstrated by a practical case study at the GS Hydropower Station. The results indicate that air entrapment within fractures significantly delays rainwater infiltration, accelerating the transition from the flow boundary to the pressure boundary at the infiltration end of the fractures. This ultimately mitigates the progression of slope instability. Additionally, the choice of relative permeability models is found to critically influence both rainfall infiltration behaviour and the subsequent slope stability evolution. The results may provide a helpful reference for hazard assessment and control of rainfall-induced landslides in fractured rock slopes.

Loess and red clay, as special soils, are widely distributed in northwest and southwest China. Their strength significantly decreases under water action, especially under rainfall, making them prone to landslides. Loess landslides typically exhibit flow-slide characteristics, while red clay landslides only show sliding behavior. To investigate their failure mechanisms under water action, this study conducted ring shear tests on saturated loess and red clay from Heifangtai, Yongjing County, Gansu Province, under normal stresses of 150 kPa, 200 kPa and 250 kPa, followed by Scanning Electron Microscopy experiments. Results show: (1) Under undrained conditions, loess exhibited rapid pore pressure increase, effective stress reduction, and strain softening, with pore pressure ratio ≥ 1 indicating liquefaction tendency; red clay showed rapid pore pressure decrease, effective stress increase, and strain hardening, with negative pore pressure ratio and no liquefaction tendency. Under drained conditions, both soils showed slight shear strength reduction. (2) During shearing, loess demonstrated increased vertical displacement with contractive behavior, while red clay showed decreased vertical displacement with dilative behavior. After-shearing, loess exhibited a loose, porous structure, whereas red clay displayed a dense structure with smaller pores and finer particles. (3) The loose structure of loess facilitates liquefaction under water, with extremely low residual strength leading to flow-type landslides; the strain hardening of red clay maintains its dense structure with closely packed particles and higher residual strength, resulting in sliding-type landslides. This study clarifies the mechanistic differences between loess and red clay landslides, providing theoretical insights for landslide prevention.

As one of the most catastrophic types of soil erosion, collapsing gully erosion with an extremely high sediment transfer rate has caused extensive soil loss and land degradation in southern China. The disintegration of granite residual soil (GRS) is widely acknowledged to be decisive for the formation and development of collapsing gully erosion. However, how soil particle composition—the most basic but no less important soil property—influences the disintegration behavior of GRS is yet to be clarified. In this study, systematic disintegration tests were performed on natural GRS obtained from various depths as well as reconstituted soil with different particle compositions, thereby establishing how the particle composition controls the disintegration of residual soil. The test results show that the particle composition affects the disintegration behavior of natural and reconstituted GRS differently. While it dominates the disintegration of reconstituted soil, with coarser particle composition corresponding to less-stable behavior, particle composition is not the critical factor for natural soil. Instead, the relic structure inherited from the parent rock plays an essential role via the interparticle cementation associated with iron-bearing minerals as well as the fissures formed by mineral leaching. Also, the effect of soil structure is quantified and found to correlate well with the disintegration parameters. This study provides new insights for soil erodibility evaluation, showing that the importance of soil particle composition has seemingly been overstated for natural residual soil from highly eroded areas and that the soil structure should receive more focus.

The typical water sensitivity of loess is the main factor affecting the instability and destruction of infrastructure on the Loess Plateau. Due to frequent dry-wet cycles(D-W cycles) caused by seasonal rainfall, groundwater level fluctuations, and other conditions, loess is often in an irreversible state of cumulative damage. In order to explore the impact of D-W cycles on the structural properties, the D-W cycles test, Scanning electron microscope test, and unconfined compression test were used. The effects of D-W cycles (D-W cycles times N, lower limit water content w₁) on the basic physical properties, mechanical properties, energy storage characteristics, and microstructure of loess were revealed. Results show that the mechanical properties are most significantly affected during the initial D-W cycle. As the w₁ increases, the reduction in strength attributable to the first D-W cycle ranges from 169.65 kPa to 5.64 kPa, representing a decrease of 15.24%. The application of energy conservation principles has elucidated that the energy storage characteristics of loess are compromised by D-W cycles. Based on the D-W durability index D_i and water stability coefficient K_i, the initial structural parameters M is established. Verification of the evolution of initial structural parameters was achieved by correlating basic physical properties, strength parameters, and energy storage characteristics. Structural parameters provide a quantitative description method that can accurately capture the structural evolution of loess during D-W cycles. The research results provide a significant theoretical reference for disaster prediction in collapsible loess areas.

This study compares the hydro-mechanical behaviour of intact and compacted Nanning stiff clay specimens under varying suction conditions using suction-controlled oedometer tests. All specimens were equilibrated at different suctions (0–38 MPa) and subjected to stepwise loading and unloading. Results showed that intact specimens exhibited insignificant suction-induced axial strain due to constraining effect of original diagenetic bonds on clay mineral activity. Both types of specimens displayed reduced compressibility with increasing suction. Upon unloading, rebound curves transitioned from bi-linear to linear as suction increased, indicating the competition between physico-chemical and mechanical effects in soils. The yield stress of the intact specimen was higher than that of the compacted one at suctions below 4.2 MPa, but lower at higher suctions (9, 21 and 38 MPa). Such phenomena were associated with the remoulding effect on the microstructure configuration of soil. Further comparison of rebound curves within the sensitive suction range (0–9 MPa) revealed that, diagenesis bonds in the natural stiff clay can be damaged by hydro-mechanical loads, leading to structural degradation. As a result, physico-chemical effects are activated during unloading, causing distinct rebound. However, residual bonds still impose certain mechanical constraints to resist the activated physico-chemical effect, resulting in a concave-down rebound curve.

The upper reservoir dam of a pumped storage power station in Shandong Province, China, has experienced leakage. The maximum measured seepage flow on June 7, 2024, was 53.7 L/s. To accurately locate the leakage inlet, this study integrated flow field fitting, robotic inkjet inspection, and NaCl tracer testing. The experimental results show that the peak potential difference at the leakage point reached 0.28 mV, which is more than four times the background potential difference (approximately 0.06 mV). The injected ink will immediately form visible ink marks and move downstream. The tracer experiment showed that a distinct peak in conductivity occurred at the downstream monitoring point UPy-4, with a conductivity variation range of 400–440 µS/cm, and there was connectivity with the deployment point UPy-2. The results obtained from these three experimental methods all show obvious spatial correlations. This case study confirms that the multi-method approach combining flow field fitting, robotic inspection, and tracer testing enhances detection accuracy for complex leakage channels, enabling precise localization at the 8# panel joint on the right bank of the reservoir.

Fluid (composed of fines and water) and its interaction with solid (coarser grains) are thought to greatly affect debris-flow behaviors. However, the high variability of the proposed cutoff diameter between the fines in fluid and coarser grains would seem to indicate that additional fluid is nonexistent in debris flows. The presence or absence of fluid in fully developed debris flows is here investigated. Results show that in debris-flow slurries fluid independent of coarser grains is nonexistent or negligible. Field evidence, including close observations of 124 moving debris-flow surges and comprehensive inspection of 64 surge deposits, indicates the en masse propagation and deposition of solid particles and water, i.e., the absence of additional fluid in debris-flow slurries. The lack of fluid in the fronts of 80 experimental debris-flow deposits, Solidity values of the deposits approaching 1, the massive structure of 32 sediments evolving from the experimental slurries, and the Bingham behavior exhibited by 80 experimental slurries consistently demonstrate that fluid is not present in debris flows, and that debris flows themselves can be regarded as continuum single-phase fluid. The degrees of saturation of > 108% of 80 slurries, determined using soil mechanics methods, indicate that debris flows are water-supported, and that the sediments in debris flows do not constitute porous media. The sustained high excess water pressure and very low cumulative percentage of decant water suggest that two mechanisms are simultaneously at work in debris flows: water supporting grains and granular assembly holding water.

Loess soil consists of fine-grained sediments deposited by wind, creating a porous structure that can be significantly affected by changes in hydro-mechanical loading conditions. Furthermore, due to its composition primarily consisting of silty deposits, loess soil is susceptible to erosion induced by water or air movement. This study aims to improve the strength and dynamic properties of loess soil by an efficient and environmentally friendly method called microbial-induced calcite precipitation (MICP), which is a proper alternative for using materials incompatible with nature, such as lime, cement, and chemical substances in soil. Sporosarcina pasteurii with an optical density of 1 has been used for microbial calcite cementation. The effects of curing time (3, 7, and 28 days) and various normal stress levels (100, 200, and 300 kPa) at shear strain amplitudes in a range of 0.05% to 1% have been investigated. Also, 1.5% natural basalt fiber has been considered to promote the performance of MICP. A series of unconfined compressive strength (UCS), cyclic direct simple shear (CSS), and bender element tests have been conducted to evaluate the dynamic characteristics such as shear modulus (G), damping ratio (D), and small-strain shear modulus ((:{text{G}}_{text{max}})) of natural soil and treated ones. Scanning electron microscopy (SEM) has been used to confirm the results. The results indicated the positive effects of the employed treatments on the dynamic characteristics of loess soil. Utilizing the MICP technique and the MICP with basalt fiber has enhanced the shear modulus of the loess soil by up to 25% and 49%, respectively.

Accurate prediction of water inflow is critically important in engineering for preventing and mitigating water inrush disasters during tunnel construction. This study introduces a novel dynamic prediction model that integrates multi-source advanced geological forecast data and proposes a water inflow prediction methodology grounded in non-Darcy flow theory. The developed model effectively captures the nonlinear characteristics inherent in water inrush processes and accommodates the spatiotemporal evolution of hydrogeological conditions throughout tunnel excavation. Key parameters for water inflow computation were derived from advanced geological prediction data, while dynamic forecasting was accomplished through the combined application of groundwater dynamics theory and entropy-weighted analysis. The results demonstrated that static water inflow exhibited an exponential relationship with seismic wave velocities, the permeability coefficient followed a power-law function with apparent resistivity, and dynamic water inflow decayed following a negative exponential function. The comprehensive water inflow showed positive correlations with both the permeability coefficient and groundwater depth while exhibiting negative correlations with the non-Darcy flow coefficient and decay rate. Furthermore, the decay rate of water inflow was positively correlated with the decay coefficient. A comparative analysis with existing methods, field monitoring data, and numerical simulations confirms the effectiveness of the proposed method. This method has been successfully implemented in a mountain tunnel project in Southwest China, with prediction errors maintained below 5%. The proposed method provides valuable technical support for the early warning and risk management of water inrush hazards in tunnel engineering.