The seismic performance of concrete-faced rockfill dams (CFRDs) in deep overburdens is a hot research topic in geotechnical engineering. In this study, the dynamic interaction mechanisms between the deep overburden and CFRD were systematically analyzed under different seismic magnitudes and impoundment conditions using a large-scale shaking table test. The geological model consists of a deep overburden and CFRD. The acceleration and energy changes at key locations were recorded and analyzed. The results show that the deep overburden has a double modulation effect on earthquakes, showing an amplification effect at low magnitudes; with the increase in input magnitude, the amplification effect is weakened, and an attenuation effect is shown. The weak interlayers in the deep overburden showed selective filtering of band energy with high-frequency energy (20–45 Hz) dissipation and low-frequency energy (1–10 Hz) amplification. The enrichment of low-frequency energy was further enhanced under impoundment conditions, leading to prominent long-period vibrations. The results revealed a complex regulation mechanism of the dam-foundation system in a deep overburden under seismic action. It provides experimental support and a theoretical reference for seismic optimization design and seismic safety assessment of CFRDs on deep overburdens.
Conventional deterministic stability analyses of geosynthetic-reinforced embankments often overlook the uncertainties inherent in soil properties, potentially leading to false identification of failure mechanisms and an underestimation of risk levels. This study employs a random upper-bound finite element limit analysis (RUBFELA) method to investigate the failure probabilities and failure modes of geosynthetic-reinforced embankments founded on soft soils with spatially varying and linearly increasing undrained strength under the framework of Monte Carlo simulation. Design charts covering a broad range of dimensionless parameters are also developed to present the probabilistic outcomes, providing engineers with reliable guidance. The analysis reveals that the interaction among geosynthetic strength, soil spatial variability, and geometric parameters can lead to counterintuitive phenomena, resulting from transitions in failure mechanisms. These transitions significantly alter the risk profile, often leading to an underestimation of associated risks if they are neglected. Furthermore, this study introduces a probabilistic analytical framework that integrates a modified limit equilibrium method with the inverse first-order reliability method, allowing engineers to efficiently assess risk levels in the presence of these uncertainties.
This study systematically examined the temperature- and time-dependent behavior of the reaction solution (RS), as well as investigated the effect of uniformity on the strength response of soil treated with enzyme-induced calcium carbonate precipitation (EICP). Both microscale and specimen-scale analyses were conducted to explore the influence of RS state on the CaCO3 distribution and the mechanical properties. Then, a uniformity evaluation method for EICP-solidified soils was proposed based on the CaCO3 content (CCC), a relationship between the uniformity coefficient (U) and strength was established accordingly. The results show that when the temperature below 5 °C, the RS exhibited negligible CaCO3 precipitation phenomenon within 12 h. The formation of white flocculent caused inlet-clogging and resulted in non-uniform CaCO3 distribution along the grouting direction. The corresponding strength varied by up to 14 times with a difference in average CCC of less than 2.8
Natural rocks often contain geometrically irregular, multiscale discontinuous pores, which significantly influence their mechanical behavior. Quantitatively assessing the relationship between pore structures and mechanical properties remains challenging for analytical and experimental approaches. This study proposes a microscale numerical approach that integrates a two-dimensional image-based reconstruction method for generating three-dimensional digital rock cores (DRCs) with a phase-field cohesive zone model (PF-CZM) to quantitatively investigate the relationship among digital core microstructure, mechanical responses, and fracture mechanisms at the representative microstructural domain (RMD) scale. The optimal RMD size is determined using the box-scaling method in conjunction with the PF-CZM, by analyzing the porosity evolution and mechanical properties within the 3D DRCs. Subsequently, 3D reconstructions are generated from a single 2D image using a simulated annealing (SA) algorithm at RMD scale. Fracture simulations based on the PF-CZM are then performed to analyze the mechanical response. The accuracy and validity of the reconstructed DRC models are systematically evaluated from both geometric and mechanical perspectives. The geometric parameters, statistical characteristics, and mechanical responses of the reconstructed digital rocks are in close agreement with those of the reference model, demonstrating the reliability of the proposed approach.
Bentonite is widely employed in landfill liners for hazardous waste containment owing to its strong adsorptive and swelling capacity. However, alkaline industrial effluents can induce significant degradation, impairing its hydraulic performance. This study investigates the influence of NaOH solutions on the swelling and permeability of bentonite through swelling and consolidation tests. Results indicate that elevated alkalinity reduces the swelling rate and increases the permeability coefficient. XRD analyses confirm a progressive decrease in montmorillonite content with increasing NaOH concentration, which directly explains the loss of swelling ability. SEM observations reveal that alkaline conditions cause montmorillonite particles to fragment and aggregate into clusters, forming larger inter-aggregate seepage channels. MIP data further corroborate a shift in pore size distribution from small to larger pores, facilitating more permeable pathways. The swelling behavior was modeled using an e–pe fractal approach, where e is the void ratio and pe denotes effective stress incorporating osmotic suction. Fitted parameters show that the swelling coefficient η decreases with montmorillonite content, while the fractal dimension Ds increases due to microstructural coarsening. By incorporating the number of montmorillonite layers (ns), the permeability–void ratio relationship was refined. A predictive model for permeability under external load was developed and validated against experimental data. This work clarifies the microstructural evolution of bentonite under alkaline attack and provides a theoretical basis for predicting its long-term engineering performance.
With the rapid development of railway and highway infrastructure across the seismically active Tibetan Plateau, understanding the liquefaction behavior of local plateau lacustrine deposits has become increasingly important. This study investigates the liquefaction resistance of Zanda silty through a comprehensive series of undrained cyclic simple shear tests, considering the effects of consolidation pressure, relative density, initial shear stress ratio (α), and cyclic shear stress ratio (CSR). Both the individual and coupled effects of these factors were quantitatively evaluated using novel SHapley Additive exPlanations (SHAP) analysis. The distinctive mechanical behavior of Zanda silty sand is revealed, and a groundbreaking framework for multi-factor soil analysis is also established. The results show that the adverse interaction between α and CSR becomes more pronounced with increasing α. Zanda silty sand exhibits relatively low sensitivity to relative density and a non-monotonic relationship between liquefaction resistance and initial vertical stress. In addition, a critical cyclic loading threshold was identified, beyond which the soil structure deteriorates rapidly, leading to brittle failure particularly under high α and CSR conditions. This study provides essential insights into the behavior of plateau silty sand and offer valuable parameters for seismic design of infrastructure in the Tibetan Plateau region.
A unified constitutive framework is developed for dense fine-granular mixtures exhibiting apparent shear thinning and continuous or discontinuous shear thickening in the macro-viscous flow regime. The effective granular stress is decomposed into viscoplastic structural and suspension-stress contributions. The former is obtained from a hypoplastic model combined with a Herschel–Bulkley rheology, whereas the latter encompasses the μ (I_m) rheology and the Wyart–Cates frictional-contact transition, and shows stress-dependent jamming state. Benchmark calculations show that the proposed formulation captures the transition between shear-thinning and shear-thickening behaviour. A depth-averaged long-wave analysis further shows that non-monotonicity induced by discontinuous shear thickening may persist to promote instability in the macro-viscous flow regime.
AI-driven models have become an important tool for regional landslide susceptibility mapping (LSM). However, existing methods rarely account for heterogeneity-induced mechanism uncertainty, which often manifests as ambiguous typology boundaries among landslide units under multi-factor controls. They also fail to capture the divergent responses of landslide and non-landslide units in similar environments, weakening interpretability and generalization. This study proposes a regional LSM framework based on unsupervised clustering and heterogeneous graph learning, aiming to explicitly encode a cluster-derived landslide typology and cross-class contrastive constraints within a unified modeling framework to improve regional-scale interpretability and predictive performance. The framework first applies unsupervised clustering to characterize latent differentiation in predisposing mechanisms among landslide slope units. It then constructs a multi-semantic heterogeneous graph from the derived typology groups and non-landslide samples: within-group consistency relations reinforce shared representations, while cross-class contrast relations model divergent responses under similar environments. A confidence-driven pseudo-label strategy further enables dynamic relation updating to enhance robustness. Finally, a heterogeneous graph attention network performs probabilistic susceptibility prediction on the resulting graph. A case study in a county of Fujian Province, southeastern coastal China, shows that the proposed model achieves an AUC of 0.941, representing an average relative improvement of 17.040
Geopolymers synthesized from aluminosilicate precursors and activators offer lower carbon emissions than cement for dredged sludge (DS) stabilization. However, the high cost and energy consumption of conventional sodium silicate (SS)-based activators (sodium silicate + sodium hydroxide) hinder their widespread adoption. This study proposed a new room-temperature mixed silica fume (SF)-based activator (silica fume + sodium hydroxide) as an alternative to SS-based activators, which require high-temperature fusion/hydrothermal synthesis, for geopolymer preparation in marine DS stabilization engineering. The effects of six factors (activator content, activator modulus, aluminosilicate content, ground granulated blast furnace slag (GGBS) proportion, moisture, and content curing age) on the engineering properties (strength and workability) and microstructure of SF-based geopolymer stabilized DS were investigated. A comparative analysis of unconfined compression strength (UCS), cost, and carbon emissions was conducted among SF-based geopolymer stabilized DS, SS-based geopolymer stabilized DS, and cement stabilized DS. The results showed that reducing the activator modulus and moisture content, while increasing the aluminosilicate content, curing age, and GGBS proportion, effectively improved the UCS of SF-based geopolymer stabilized DS. The peak UCS value was achieved at a mass ratio of SF-based activator to aluminosilicate of 1:3. The setting time decreased with higher activator content, aluminosilicate content, GGBS proportion, and curing age, but increased with higher activator modulus and moisture content. Compared with conventional stabilized DS, the SF-based geopolymer stabilized DS exhibited the highest UCS, the lowest cost, and the lowest carbon emissions. Microstructural analysis revealed that the SF-based activator underwent geopolymerization with GGBS and FA to form C–A–S–H gel. This gel enhanced the compactness of the DS skeleton by cementing loose particles and filling interparticle pores, thereby accelerating hardening and improving strength of stabilized DS.
Calcareous sand foundations or seabed face numerous challenges in complex marine environments. Among these, the coupled effects of principal stress rotation and inherent anisotropy on the cyclic properties of calcareous sand remain unclear. Therefore, this study utilized an inclined sand specimen preparation apparatus (ISSPA) to prepare specimens with different bedding angles α3. Based on this, a series of principal stress rotation tests accounting for inherent anisotropy—also termed biaxial rotation of principal stress tests—were conducted. The test results indicate that pore pressure and deformation exhibit two distinct development patterns. Liquefaction resistance initially increases and subsequently decreases with increasing bedding angle α3, while it decreases with increasing cyclic stress ratio (CSR). Specimens with a bedding angle α3 of 45° demonstrate the highest resistance to liquefaction. Interestingly, the pore pressure at the strain turning point was approximately 0.83 times the mean effective pressure p′. Furthermore, both bedding angle α3 and CSR significantly influenced the stress–strain relationship. Larger bedding angles resulted in a slower stiffness decay of calcareous sand under principal stress rotation. Based on the test results, mathematical models describing excess pore pressure Δu, generalized shear strain γg, axial shear modulus Ea, and damping ratio Da were established.
Rapid water evaporation is a significant obstacle when using microbially induced calcium carbonate precipitation (MICP) technology to stabilize aeolian sand in desert environments. This results in inadequate solidification outcomes by limiting the reaction period between the bacterial solution and the cementation solution. This study proposes an MICP-water retention synergistic method for stabilizing aeolian sand using a bacterial powder made by the research team for storage and transit at room temperature. The effects of water-retaining agent dosage, bacterial solution and cementation solution volumes, temperature, and dry density on the surface strength, water retention capacity, and wind erosion resistance of samples were examined using single-factor and response surface methodology experiments. Microstructural testing methods were employed to investigate the synergistic stabilization mechanism. The results showed that as the water-retaining agent dosage increased, surface strength and wind erosion resistance increased and subsequently dropped, while water retention capacity improved. Increasing the volume of the bacterial and cementation solutions improved the mechanical characteristics, with water retention first rising and subsequently decreasing. As the temperature rose, all performance indicators first increased before declining. Dry density has no significant effect on the major performance measures. The MICP-water retention synergistic method outperformed the MICP technology alone in terms of sand stabilization efficacy. Response surface analysis indicated nonlinear interacting effects among the parameters, and the optimal values for MICP-water retention synergistic sand stabilization were determined. Microscopic examination shows that the water-retaining agent’s moist microenvironment successfully increases bacterial/enzymatic activity and reaction efficiency, guaranteeing the stabilizing result. Additionally, moisture makes it easier for the bacterial and cementation solutions to move between the sand particles, which results in the deposition of calcium carbonate at crucial contact points and strengthens the cementation as a whole. The results of this study are important for enhancing aeolian sand’s ability to stabilize surfaces in desert areas.
Long-term sustained loading and wetting–drying cycles can accelerate ionic attack and structural damage in coastal stabilized soft soils. However, the coupled effects of wetting–drying cycles and chemo-mechanical interactions under coastal exposure conditions are not yet fully understood. To address this issue, a conventional consolidation apparatus was modified to apply sustained loading while controlling wetting–drying cycles. Slag–cement-stabilized marine soft soil was exposed to freshwater, seawater, and alternating freshwater–seawater environments under different loading levels, and its strength degradation was evaluated through unconfined compressive strength tests. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and computed tomography (CT) analyses were further used to reveal the associated mineralogical and pore structural changes. Results show that erosion severity followed the order: seawater > alternating freshwater–seawater > freshwater. In the early cycles, higher loading levels caused greater strength loss, whereas in later cycles, when the applied load was below a critical threshold, strength increased markedly. The 20
The coefficient of earth pressure at rest (K0) is a fundamental parameter in geotechnical analysis and design. Its evolution under repeated loading remains inadequately understood, particularly concerning the effects of particle shape. This study systematically investigates the combined influence of particle morphology and relative density on the evolution and hysteresis of K0 using the discrete element method. Five granular assemblies with distinct, realistic particle shapes but identical particle size distributions are examined across three density states (loose, medium dense, and dense). The results show that denser specimens composed of more irregular particles exhibit lower K0 values during virgin loading. During unloading and reloading, pronounced hysteresis is observed, which becomes more significant with non-spherical particles. The unloading and reloading coefficients display clear linear correlations with various particle shape descriptors. Micromechanical analyses reveal that the hysteresis of K0 cannot be fully explained by changes in the coordination number alone but is primarily governed by the anisotropic evolution of contact force networks. The stress–force–fabric framework effectively captures the evolution of K0, emphasizing the dominant role of normal force anisotropy, while contact normal and branch vector anisotropies play a lesser role. A unified exponential relationship between K0 and normal force anisotropy is identified, which is independent of density, stress history, and particle shape. These findings offer new insights into the micromechanical origins of K0 hysteresis and its dependence on particle morphology under repeated stress paths.
To address the challenges of dredged soil disposal and scour protection for offshore wind turbine foundations, this study proposes a method for preparing fluidized solidified soil (FSS) from dredged soil for scour protection. The prepared FSS showed suitable flowability, dispersion resistance, and unconfined compressive strength (UCS) for pumped underwater scour protection: its flowability ranged from 17.0 to 30.5 cm, turbidity ranged from 17.0 to 88.4 NTU, and UCS at 28 d reached 886.30 kPa. The rheological behavior of FSS is well described by the Herschel-Bulkley model, exhibiting distinct yield stress and shear-thinning characteristics. The hydroxyl groups of hydroxypropyl methylcellulose and hydroxypropyl starch ether bond with water molecules and solid particles to enhance dispersion resistance, while their interaction with calcium silicate hydrate gel and ettringite improves the toughness of FSS. Carbon emission and economic analyses indicate that, compared with other scour protection methods, the FSS approach reduces carbon dioxide emissions by 74
This paper presents an analytical load transfer framework based on a bond–friction interface model to characterize the progressive mechanical response of rock bolt anchorage interfaces. The proposed framework divides the pullout process into three stages: elastic, debonding, and sliding, thereby describing both the initial linear elastic response and the subsequent nonlinear post-peak softening behavior. Experimental data, PFC2D numerical simulations, and existing analytical solutions are employed to validate the proposed constitutive relationship and investigate the effects of key interface parameters on the maximum pullout load. The results demonstrate that the proposed model can effectively predict the load–displacement response and axial force distribution, and reveal the progressive resistance evolution between the debonded segment and the remaining bonded segment during interface debonding. Furthermore, the proposed framework provides a practical approach for determining the effective anchorage length and is successfully applied to optimize the prestressed rock cable design in the Muzhailing Tunnel.
A series of one-dimensional, laterally confined consolidation tests was carried out on reconstituted and slurried clays. Reconstituted clay, prepared as a slurry, underwent loading and unloading in a rectangular cell in which null pressure gauges were installed in the walls, allowing reliable measurement of lateral stress. The results of the virgin loading stages showed equivalency between the compression index, C_c , which relates the void ratio to the vertical effective stress, and the critical state compression parameter, λ , which relates void ratio to the isotropic or mean effective stress, as long λ is obtained from one-dimensional compression. This equivalency is shown to be consistent with constant K_0 during virgin loading. On the other hand, during unloading, the expansion indices differed significantly, and non-equivalency was demonstrated between the parameters C_e , the expansion index, and the critical state parameter, κ , consistent with a non-constant unloading earth pressure coefficient, K_0 ^' . Isotropic consolidation tests performed on the same soils yielded compression indices, λ , consistently slightly lower—80–86 κ , were equal to the one-dimensional values. A rational expression for the relationship between K_0 ^' and K_0 , in terms of the expansion indices relative to vertical and lateral stress, respectively, C_e , C_e,h , is presented.
Monitoring shear deformation in soil is crucial for understanding the mechanical behavior of geotechnical infrastructures. Distributed fiber optic sensing (DFOS) technology provides advantages for soil deformation monitoring, but the cable–soil interfacial behavior under shear deformation remains insufficiently studied. In this study, a series of shear model tests using optical frequency domain reflectometry (OFDR) technology were conducted to investigate the response of embedded fiber optic (FO) cables under different anchorage configurations. The results showed that anchorage configuration improves the cable–soil coupling compared to unanchored cables. Additionally, a theoretical model was developed to characterize shear-induced deformation of unanchored FO cables, in which the cable–soil interaction states were delineated by a set of characteristic shear displacements. Furthermore, the shear stresses at the cable–soil interface, inferred from the step-like strain profiles of anchored FO cables, were analyzed to evaluate the contributions of different micro-anchors to the interfacial behavior between the cable and soil. This study offers both theoretical and experimental insights into the application of OFDR-based FO sensors for monitoring soil shear deformation in geotechnical engineering.
During the construction of shield tunnels, up to three rings are positioned within the shield of a tunnel-boring machine (TBM). Upon leaving the shield, the rings encounter buoyancy from the cementitious grouting slurry until it solidifies. This buoyancy generates divergent radial forces and induces longitudinal transitional forces between rings, resulting in structural deformations during construction. To investigate these effects, a novel full-scale multiring experimental study was conducted. The test subjected the top ring to grouting slurry forces, while the middle and bottom rings were subjected to water and soil forces. Key parameters examined included the distribution of grouting slurry forces, longitudinal forces, and loading levels to analyze segmental lining deformations, the mechanics of lining segments, and their connecting devices. The study demonstrated that grouting slurry forces significantly impacted segmental linings, resulting in a 17.18
In densely populated urban areas, underground excavation in hard rock faces growing constraints due to environmental concerns. Although innovative rock fracturing technologies, such as soundless cracking agents (SCAs), have emerged as safer and more environmentally sustainable alternatives to conventional blasting, their widespread adoption remains limited by relatively low fracturing efficiency. Furthermore, the lack of a reliable factor for consistently evaluating rock fracturing performance continues to hinder their effective applications in various engineering scenarios. To address this gap, we conducted a series of experimental and numerical studies to investigate the physical constraints governing rock fracturing under expansive pressure. The results show that the rock fracturing process is strongly influenced by the evolution of texture heterogeneity. The relatively homogeneous limestone exhibits failure at lower expansive pressures than the relatively heterogeneous granite. Beyond differences in intrinsic strength, limestone also shows a failure response that is less sensitive to heterogeneity. The coefficient of strain heterogeneity for a limestone sample increases monotonically up to failure, whereas the coefficient for a granite sample experiences a sudden drop before rising again until failure. The numerical simulations based on the cohesive zone model indicate that the temporary drop results from the redistribution and amplification of damage variables. The evolution of texture heterogeneity as a reliable factor for evaluating rock fracturing performance is further confirmed by numerical simulations with varying texture features and by additional experiments using different SCAs.
To address the demand for industrial solid waste recycling and low-carbon building materials, this study utilized slag, fly ash, carbide slag, desulfurization ash, and jute fiber as binding materials to prepare self-compacting solidified soil based on industrial solid waste. The durability evolution of the material under the coupled effects of dry–wet cycles and salt–dry–wet cycles was systematically investigated. Through a combination of macro- and micro-scale analyses, the strength reduction rate, mass loss rate, surface morphological changes, and stress–strain characteristics were evaluated to reveal the long-term performance degradation mechanisms of self-compacting solidified soil in complex environments. The experimental results demonstrated that salt–dry–wet cycles exhibited significantly higher erosion effects on the soil’s performance compared to ordinary dry–wet cycles, with the strength reduction rate and mass loss rate increasing progressively with cycle repetitions. The incorporation of 5‰ jute fiber reduces the strength loss rate by more than 15
