Search Results (144)

Rainfall contributes to slope instability when infiltrating water reduces matric suction and elevates pore water pressure beyond critical thresholds. Empirical rainfall intensity–duration (I-D) thresholds define the minimum rainfall conditions necessary to initiate landslides and are widely adopted in regional early warning systems. This study derives I-D thresholds for shallow landslide initiation in South-East Queensland (SEQ), Australia, using quantile regression applied to 104 rainfall-induced shallow landslide events recorded between 1974 and 2018. Thresholds at the 2nd, 10th, 50th, and 90th percentiles were derived over a duration range of 0.3 to 383 h and intensity range of 0.15 to 13.7 mm h⁻¹. The 2nd percentile, adopted as the conservative regional early warning threshold, is expressed as I = 0.719 × D^−0.220, where I is rainfall intensity (mm h⁻¹) and D is event duration (h). To facilitate inter-regional comparability, normalised thresholds expressed in terms of mean annual precipitation (MAP) were also derived, yielding a 2nd percentile threshold of I_MAP = 6.070 × 10⁻⁴ × D^−0.207. Both I-D and I_MAP -D thresholds fall substantially below existing global benchmarks, reflecting the pronounced susceptibility of SEQ’s deeply weathered residual soils to infiltration-driven failure. Independent validation against real-time tilt sensor and volumetric water content monitoring data from five kinematic failure events recorded at Maleny, Queensland (2016–2020), confirmed that all events plotted above the 2nd percentile threshold, with zero false negatives. The results provide a quantitative, operationally validated framework for regional shallow landslide early warning in subtropical Australia. Full article

Drying in granular porous media is governed by coupled thermal and hydraulic processes that can be substantially modified by biological activity. This proof-of-concept study investigated how surface heating and fungal colonization influence the evolution of thermal conductivity (λ) and matric suction (ψ) as functions of volumetric water content ${\theta }_v$ in Ottawa 20/30 sand. Four treatments were examined: sterile sand at 22 °C (T1), sterile sand at 28 °C (T2), fungal-amended sand with 10% biomass and 9-day incubation (T3), and fungal-amended sand with 15% biomass and 30-day incubation (T4). Samples were instrumented to monitor ${\theta }_v$, λ, and ψ during controlled evaporation using synchronized HYPROP and VARIOS measurements on the same specimen. Across all treatments, λ increased with ${\theta }_v$ (that is, λ declined as drying progressed), and ψ reflected the transition from hydraulically connected to disconnected pore water. Heating shortened the drying time but did not materially change the form of the λ–${\theta }_v$ relationship or generate strong matric gradients in sterile sand. Low biomass (T3) produced thermal and hydraulic responses comparable to the heated sterile control (T2), indicating limited pore-scale modification at early colonization. In contrast, high biomass (T4) widened the effective saturation range, maintained low and nearly uniform ψ across depth, and exhibited the steepest mid-range λ–${\theta }_v$ slope with a higher peak λ (~4 Wm⁻¹K⁻¹), consistent with hyphae and extracellular polymers stabilizing thin water films. A soil water retention curve (SWRC) analysis using the van Genuchten model further indicated increased water retention and delayed air entry with an increasing fungal biomass, with approximate air-entry values increasing from ~1.8 kPa (T3) to ~3.0 kPa (T4). Tests were terminated upon tensiometer cavitation rather than complete gravimetric dryness, constraining observations at very low ${\theta }_v$. These results indicate that heating primarily affects the rate of drying, whereas fungal networks alter the pathway by preserving hydraulic and thermal continuity at relatively high ${\theta }_v$. This behavior suggests a potential role of bio-mediated structuring in influencing near-surface thermo-hydraulic processes relevant to energy foundations, soil covers, and desiccation management in biologically active or bio-engineered soils. Full article

Expansive soil slopes are highly susceptible to rainfall-induced shallow failures due to cyclic swelling–shrinkage behavior governed by matric suction variation. This study proposes a composite frame–geosynthetic system (CFGS), comprising a rigid frame integrated with high-performance turf reinforcement mats (HPTRMs), for expansive soil slope protection. The performance of the CFGS was evaluated through geometrically scaled, materially representative physical model tests under repeated wetting–drying cycles and further examined using coupled hydro-mechanical numerical simulations in COMSOL Multiphysics. A bare slope and an HPTRM-protected slope were used for comparison. Under identical laboratory conditions, CFGS reduced cumulative erosion to approximately 13% of that of the bare slope. It also moderated the internal hydraulic response, reducing pore-water pressure fluctuation by approximately 26%, and restrained swelling–shrinkage deformation, with an average deformation attenuation of up to 61%. The numerical simulations showed consistent response trends with the physical model tests, supporting the proposed mechanism of hydraulic regulation, deformation restraint, and stress redistribution. Overall, the results demonstrate the comparative effectiveness of CFGS in mitigating wetting–drying-induced deterioration of expansive soil slopes. Full article

Given the escalating impacts of global climate change and extreme weather events, the accurate stability assessment of rainfall-induced landslides necessitates a comprehensive consideration of both seepage processes and the inherent spatial variability of soils. Traditional deterministic and two-dimensional (2D) analyses often fail to capture the multi-dimensional kinematic features of slope failures and the stochastic nature of soil heterogeneity, thereby leading to inaccurate risk assessments. This study proposes a three-dimensional (3D) slope reliability analysis framework. Within this framework, a 3D slope geometric model is constructed using GeoStudio 2025.1.0 software, and seepage analysis is conducted by the SEEP3D module. To account for soil spatial variability, the Karhunen–Loève (K-L) expansion method is employed to discretize key shear strength parameters (effective cohesion and effective angle of internal friction). The factor of safety (F_s) is evaluated using the 3D simplified Bishop method, which is then coupled with Monte Carlo simulations to determine the probability of failure (P_f). The results show that rainfall infiltration causes progressive dissipation of shallow matric suction and a significant rise in the groundwater table near the slope toe, resulting in reduced effective stress in the critical resistance zone. As rainfall intensity increases, the F_s decreases approximately linearly from 1.14 to 0.90, whereas the P_f increases nonlinearly from nearly 0 to 98.36%. Under the rainstorm condition, although the F_s remains above unity at 1.063, the corresponding P_f reaches 23%, indicating that deterministic evaluation based only on the F_s may underestimate the actual failure risk. The proposed framework provides a quantitative tool for evaluating rainfall-induced slope instability by integrating transient hydraulic response, three-dimensional spatial variability, and probabilistic reliability assessment. Full article

Under long-term cyclic loading, the cumulative plastic deformation of unsaturated sandy subgrade is a key control factor for the pavement’s service performance. However, its evolution mechanism and quantitative characterization still lack a universal model. In this study, based on the GDS dynamic triaxial system, a series of cyclic tests were conducted under different conditions: matric suction from 0 to 90 kPa, net confining pressure from 30 to 120 kPa, dynamic stress amplitude from 60 to 240 kPa, and compaction degrees of 87–96%, reaching a total of 10,000 cycles. The results reveal that the permanent deformation of unsaturated sandy subgrade material evolves through three stages: fast, slow, and stable. The deformation is exponentially negatively correlated with matric suction, net confining pressure, and compaction degree, and exponentially positively correlated with dynamic stress amplitude. A coupling prediction model was developed by embedding matric suction and compaction degree factors into the Karg model. This model incorporates net confining pressure, dynamic stress amplitude, matric suction, and compaction degree. By using a normalized master curve method, the permanent deformation curves under different working conditions were compressed into a unique dimensionless function. The parameters have clear physical significance and allow for a unified description across stress, suction, state, and soil types. Experimental data, along with data from the literature, were used to validate the model, showing prediction errors of less than 10% and R² > 0.95. The model provides a simple, high-precision, and transferable theoretical tool for long-service-life subgrade deformation control. Full article

Fiber-reinforced cemented tailings backfill (FTB) has been widely adopted in underground mining operations as an effective solution for mitigating the brittleness of cemented tailings backfill (CTB) and ensuring compatibility with deep mining environments. Understanding the coupled effects of temperature and binder composition on the thermal–hydro–mechanical–chemical (THMC) behavior of FTB is essential for low-carbon mix design and practical application. To address this knowledge gap, this work presents a systematic investigation into the influences of curing temperature, binder type, and cement content on the rheological properties, compressive strength, and THMC-related parameters of FTB. The results demonstrate that elevated temperatures accelerate hydration, reducing flowability while significantly enhancing strength and pore structure refinement. Conversely, low temperatures preserve flowability but impede strength development. The incorporation of slag or fly ash as partial cement substitutes reduces rheological parameters; however, fly ash substitution tends to compromise ultimate strength. Multi-field performance monitoring further reveals the underlying coupling mechanisms among temperature evolution, hydration kinetics, matric suction, and mechanical strength development. Based on these insights, a low-carbon design strategy is proposed, emphasizing dynamic optimization of cement content according to ambient temperature. These findings offer a theoretical foundation for the sustainable proportioning and performance control of mine backfill materials. Full article

As one of the most catastrophic geological hazards globally, landslides exhibit heightened risks due to their increasing frequency, destructive potential, and extensive spatial distribution. The primary objective of this study is to develop an integrated analytical framework to quantitatively evaluate the stability of variably shaped slopes under rainfall infiltration. The core hypothesis is that slope curvature significantly alters infiltration behavior and stress distribution, leading to morphology-dependent failure mechanisms. Employing Green-Ampt infiltration theory coupled with limit equilibrium analysis, we establish stability prediction models for three fundamental slope geometries (linear, concave, convex) under contrasting rainfall regimes (high-intensity vs. low-intensity precipitation). The derived analytical solutions reveal two critical phenomena: (1) progressive downward migration of the saturation front maintaining parallelism with slope surfaces during infiltration and (2) time-dependent stability deterioration following hyperbolic decay patterns. The proposed models are rigorously validated through numerical simulations employing finite element methods, which demonstrate remarkable congruence with theoretical predictions, showing safety factor discrepancies below 5% (ΔFs < 0.05). Particularly, concave slopes exhibit 18–22% faster destabilization rates compared to convex counterparts under equivalent rainfall conditions. The validated models elucidate the spatiotemporal evolution of matric suction and pore pressure distributions, providing quantitative insights into morphology-dependent failure thresholds. These findings advance predictive capabilities for rainfall-induced landslides through physics-based stability criteria, offering critical guidance for terrain-specific early warning systems and mitigation strategies in geohazard-prone regions. Full article

Climate-driven extremes in temperature and precipitation are increasingly threatening the stability and serviceability of slopes, embankments, levees, transportation corridors, and other earthen infrastructures founded on expansive and problematic soils. Conventional stabilization strategies, which often treat reinforcement and drainage as separate design elements, struggle to cope with cyclic wetting-drying, freeze-thaw, and prolonged rainfall events that drive desiccation cracking, loss of matric suction, elevated pore-water pressures, and progressive strength degradation. This paper presents a state-of-the-art review of geosynthetic-reinforced slopes with particular emphasis on geogrid geotextile composite systems and their performance under high-temperature, high-rainfall, and low-temperature environments. We first summarize the fundamentals of geosynthetic types, functions, and material properties, then examine how thermal and hydrological processes such as creep, oxidation, frost heave, infiltration, suction loss, and pore-pressure build-up govern the performance of geosynthetic-reinforced soil (GRS) systems. Next, we synthesize recent advances in composite geosynthetics that integrate reinforcement, filtration, separation, and drainage, highlighting laboratory studies, centrifuge modeling, numerical analyses, and field case histories for mechanically stabilized earth walls, pavements, railway embankments, levee systems, and rainfall-induced and expansive soil slopes. Across these applications, geogrid geotextile composites consistently improve hydraulic control, maintain effective stress, and enhance factors of safety under extreme climatic loading. The review concludes by identifying critical research gaps, including coupled thermo-hydro-mechanical characterization, performance-based design approaches, and climate-resilient guidelines for geosynthetic selection and detailing. These findings underscore the potential of composite geosynthetics to enable more sustainable and resilient slope and earthwork infrastructure in a changing climate. Full article

Reinforced-soil structures in rainfall-prone regions may deform or fail when infiltration weakens the geogrid–soil interface. This study quantifies the degradation of unsaturated shear strength at a geogrid–sandy-soil interface during rainfall infiltration. A large-scale direct shear apparatus was retrofitted with a controllable rainfall system and real-time water-content monitoring. Interface shear tests were conducted under different normal stresses, rainfall intensities, infiltration durations, and shear rates. Peak interface shear strength increased approximately linearly with normal stress and remained about 50% higher than that of unreinforced sand. Rainfall infiltration caused pronounced strength loss; at 120 mm·h⁻¹, extending infiltration from 10 to 30 min reduced apparent cohesion by ~56% and friction angle by ~23%. Cohesion decayed exponentially, whereas friction angle decreased nearly linearly, and faster shearing intensified both reductions. Response-surface regression further indicates that degradation is most severe under low normal stress, high rainfall intensity, and long infiltration duration. Water-content profiles reveal a persistent moisture-enriched zone adjacent to the shear plane (~3.4% higher than at 30 mm depth), implying reduced matric suction and promoting shear-band localization that accelerates interface weakening. These findings provide quantitative input for evaluating rainfall-induced performance loss of geogrid-reinforced soil structures. Full article

Intensive agricultural mechanization in Northeast China has exacerbated soil compaction and degraded water retention. Although biochar modifies soil hydraulics, its combined effect with matric suction on compressive behavior remains unclear. This study investigated the hydraulic and mechanical responses of repacked sandy clay brown soil to biochar (0, 0.5, 1 g kg⁻¹) under varying matric suction (6–1000 kPa). We utilized water retention curves and uniaxial compression tests to assess mechanical properties, including pre-compression stress (σ_p), penetration resistance (PR), compression index (Cc) and swelling index (Cs). Additionally, an integrated model using the Entropy Weight Method (EWM), the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), and the Adversarial Interpretive Structure Model (AISM) was developed to evaluate soil resistance and resilience. Results indicated that 1 g kg⁻¹ biochar significantly enhanced field capacity (θ_FC) and readily extractable water (θ_MRE) (p < 0.05). While individual factors influenced all mechanical properties, the biochar–suction interaction significantly affected pre-compression stress and the compression index (p < 0.05). The model identified 1 g kg⁻¹ biochar at 1000 kPa suction as the optimal combination for maximizing soil structural stability. These findings highlight the critical role of biochar–matric suction interactions in accurately assessing and managing soil mechanical behavior. Full article

Temperature and seepage are critical factors influencing the stability of unsaturated retaining walls, as they modulate soil shear strength through alterations in matric suction. This study proposes a three-dimensional analytical framework for evaluating active earth pressure under thermal and seepage conditions. With a kinematic upper-bound approach, temperature-dependent suction evolution and steady-state seepage are incorporated into a horn-shaped failure mechanism. The proposed method is validated against published analytical/numerical solutions, confirming its reliability. A systematic parametric study is conducted to examine how temperature, seepage velocity, wall geometry, and soil pore characteristics affect the active earth pressure behavior. The results reveal distinct behavioral trends depending on soil type: for sand, the active earth pressure increases with rising temperature, indicating reduced stability; conversely, for clay, it decreases with temperature elevation, suggesting enhanced stability. While seepage has minimal impact on sand, it exhibits a clear directional dependence in clays, with infiltration increasing active thrust and evaporation promoting stability through suction recovery. Three-dimensional analysis yields substantially lower earth pressure values compared with conventional two-dimensional approaches, highlighting potential design economies. The proposed method provides engineers with a practical tool for coupled thermal hydraulic mechanical analysis of retaining walls in unsaturated fills, facilitating more realistic and cost-effective designs under varying environmental conditions. Full article

To enhance the assessment accuracy of tunnel face instability risks of active collapse during shield tunneling, this study establishes a novel unified analytical framework that couples the effects of unsaturated transient seepage induced by excavation drainage with soil stratification and heterogeneity. Grounded in unsaturated effective stress theory, the framework explicitly incorporates matric suction into the Mohr–Coulomb failure criterion via suction stress and apparent cohesion. By employing a horizontal two-layer nonhomogeneous soil model and solving the one-dimensional vertical Richards’ equation, an analytical solution for the face drainage boundary is derived to quantify the spatiotemporal evolution of suction stress and apparent cohesion. Subsequently, the critical support pressure is evaluated using the upper bound theorem of limit analysis, incorporating a horizontal layer-discretized rotational failure mechanism and the power balance equation. The validity of the proposed framework is confirmed through comparative analyses. Parametric studies reveal that in the upper hard and lower soft strata, the critical support pressure decreases and converges over time, indicating that unsaturated transient seepage exerts a significant influence in the short term that stabilizes over the long term. Additionally, sand–silt stratum exhibits lower overall stability and higher sensitivity to groundwater levels and temporal factors compared to silt–clay stratum. Conversely, silt–clay stratum displays a non-monotonic evolution with increasing cover-to-diameter ratios ($C/D$), reaching a minimum critical support pressure at approximately $C/D=1.1$. Regarding heterogeneity, the internal friction angle of the lower layer exerts dominant control over the critical support pressure compared to seepage velocity, while the influence of other strength parameters remains secondary. These findings provide a theoretical basis for the time-dependent design of tunnel face support pressure under excavation drainage conditions. Full article

Tailings sand primarily consists of fine sand, silt, and other non-cohesive soil particles. Due to its persistent saturation, it exhibits a high susceptibility to liquefaction under dynamic loading or fluctuating groundwater conditions, potentially leading to engineering failures such as foundation instability and slope failure. This study focuses on a representative tailings pond located in the northwest region of China. A series of geotechnical laboratory tests were conducted to investigate the fundamental physical and mechanical properties of tailings sand. The test results indicate that moisture content increases gradually with depth and stabilizes beyond a certain depth, while dry density decreases approximately linearly with increasing depth. Owing to the presence of certain metallic minerals, the specific gravity of tailings sand materials is slightly higher than that of conventional standard sand. Particle-size analysis reveals that the non-uniformity coefficient ranges from 2.04 to 3.1, and the coefficient of curvature varies between 0.72 and 0.97, indicating poor gradation. Compaction testing determined an optimum moisture content of 13.59%, corresponding to a maximum dry density of 1.868 g/cm³. Soil-water characteristic curve analysis shows that larger particle sizes are associated with enhanced drainage capacity and lower suction requirements. An increase in dry density significantly reduces the drainage rate but has a limited effect on the matric suction at the residual stage. This research provides valuable insights into the engineering behavior of tailings sand, supports the assessment of its performance in foundation applications, and offers practical guidance for the stabilization of and improvement in tailings sand foundations. Full article

In the loess region, the hydraulic properties of the loess, used as either surrounding rock, backfilling or geoplomer material, are significant for engineering construction and agriculture development projects. This work investigated the soil-water characteristic curves (SWCC) of the undisturbed and remolded loess during the drying process using the tensiometer and psychrometer method. Based on the test results, SWCC was fitted using the Van Genuchten, and Fredlund and Xing models. Moreover, the permeability was comparatively calculated by the Childs and Collis-George, Van Genuchten, and Fredlund models, respectively. Results revealed that the SWCC of both the undisturbed and remolded loess exhibited three-stage characteristics in the relationship between the logarithmic matric suction and moisture, including the boundary effect zone, transition zone, and residual zone. The corrected Fredlund and Xing model provided an optimal calculation for the SWCC of the loess, while the Van Genuchten model showed suction deviations of about 103 kPa. Meanwhile, the undisturbed loess had a low water retention at the low (<103 kPa) suction range, which was attributed to the large pore structure of the undisturbed loess that reduces the air-entry value. This research clarified the differences in the water retention and permeability properties of the loess, providing a theoretical foundation for evaluating the hydraulic properties of the loess. Full article

The stability of bank slopes in pumped storage power stations is crucial, particularly in regions where frequent water level fluctuations occur. This study aims to investigate the degradation mechanism of bank slope under such fluctuating conditions, focusing on granite residual soil from the pumped storage power stations in Fujian, China. To explore the effects of drying-wetting cycles and matric suction on soil shear strength, drying and wetting cycles were conducted with unsaturated triaxial shear tests. The results revealed that the shear parameter strengthening effect occurs when the matric suction increases from 50 kPa to 200 kPa. Moreover, during the first five drying-wetting cycles, soil shear strength decreased sharply, with cohesion and internal friction angle decreasing by approximately 15.4% and 11.2%, respectively. This degradation trend stabilized in the later cycles. Scanning Electron Microscopy (SEM) analysis of the soil microstructure showed an evolution from a dense structure to a penetrating cavity during the cycles. This change reflects that the strength degradation characteristics of granite residual soils are controlled by the synergistic effects of structural and frictional mechanisms, manifesting as initial degradation followed by stabilization. Additionally, by fitting the nonlinear characteristics of the experimental data, shear strength evolution functions for matric suction and drying-wetting cycles were established, revealing the effect of these factors on strength degradation. These findings provide a theoretical basis for the stability analysis of bank slopes in pumped storage power stations, offering insights into soil behavior under fluctuating water levels. Full article