Red mud, a bulk solid waste generated by the alumina industry, is commonly stockpiled for long periods, which can induce environmental and geotechnical risks such as low pile strength and insufficient stability. Conventional cement stabilization, however, is constrained by high carbon emissions and limited immobilization efficiency. In this study, a low-carbon, all-solid-waste binder system for red mud stabilization was developed using steel slag, fly ash, and phosphogypsum as multi-source industrial solid wastes, and the mix proportions were optimized via the simplex centroid method. Results show that at a red mud/steel slag/fly ash/phosphogypsum mass ratio of 54:9:27:10, the system synergistically forms hydration products including calcium silicate hydrate (C-S-H), calcium aluminosilicate hydrate (C-A-S-H), and ettringite (AFt). The stabilized material achieved a 90-day compressive strength of approximately 14 MPa and a hydraulic conductivity of 7.4×10⁻⁷ cm/s. Consolidated undrained (CU) triaxial tests yielded a cohesion of approximately 13 kPa and an internal friction angle of approximately 30°, indicating pronounced improvements in the strength and stiffness of the stabilized material. The immobilization efficiency of Na⁺ was 63.5%, and those of heavy metals such as Pb, As, and Cr were all no less than 75.0%, with leachate concentrations below the corresponding leaching toxicity limits. After coupled freeze–thaw and salt-erosion exposure, both mass loss and strength degradation remained low, demonstrating favorable durability. These findings provide a low-carbon technical basis for in situ stabilization and resource-oriented utilization of red mud stockpiles.

This study selected shale from the Longmaxi Formation in Sichuan as the research object. The shale samples were subjected to microwave irradiation at 2,450 MHz and 800 W for 0, 15, 30, 60, and 90 s. By integrating computed tomography (CT), uniaxial compression tests, and numerical simulation of the temperature field, the microwave-induced evolution of the pore structure and the degradation of macroscopic mechanical properties were systematically analyzed, and their response relationship between them was revealed. The results show that: (1) Microwave irradiation significantly promotes the generation and propagation of pores in shale. After 90 s of microwave irradiation, the number of pores increases by about 88.4%, the porosity rises from 4.1% to 10.7%, both the maximum and average pore radii increase markedly, and the pore size distribution tends to be multi-scale. The thermal effect induced by microwave irradiation is the dominant factor controlling pore development, showing significant regional and heterogeneous characteristics, and is significantly correlated with the degradation of macroscopic mechanical properties. (2) Microwave irradiation significantly enhances pore connectivity. The three-dimensional pore-throat network model shows that after 90 s of microwave irradiation, the number of throats increases by about 109.1%, the average pore-throat radius increases by about 11.7%, and the coordination number increases by 103.3%; the pore connectivity and complexity improve simultaneously, and the pore structure evolves from discrete micro-nano pores to a mesoscopic connected structure. (3) The pore structure evolution of shale under microwave irradiation reflects its structural damage characteristics, and the damage variable constructed based on porosity can effectively reflect the structural deterioration process of shale under thermo-mechanical action. The modified multivariate regression model shows that the pore number, throat number and coordination number can predict the damage evolution process of shale with high accuracy. (4) Microwave irradiation leads to continuous deterioration of shale strength and stiffness, and the failure mode gradually transforms from splitting failure characterized by a single main crack to multi-crack intersecting failure. The results can provide theoretical and methodological support for microwave-assisted unconventional oil and gas extraction and directional weakening of rock mass.

The construction of China's first deep underground research laboratory (URL) for high-level radioactive waste (HLW) geological disposal has commenced in the Beishan area, Gansu Province, and the surrounding rock of the URL is mainly granite. Accurate characterization of the mechanical properties of deep Beishan granite is crucial for ensuring the long-term safety and structural stability of the repository. Traditional macroscopic mechanical testing methods, such as uniaxial compression tests, yield scattered data and entail high costs and logistical challenges associated with deep borehole coring. To address these limitations, this study integrates nanoindentation experiments with finite-element numerical simulations to precisely characterize the mechanical behavior of Beishan granite under complex thermo-stress coupling conditions. Nanoindentation results were employed to validate the finite-element model, which was subsequently applied to investigate the response of granite under varying temperature and stress fields. The key findings are as follows: (1) The elastic modulus measured by nanoindentation reached 70.66 GPa, higher than the 62.39 GPa obtained from conventional uniaxial compression tests, highlighting the ability of this method to capture localized micromechanical properties. (2) The validated finite-element model reliably simulates the thermo-mechanical responses observed in nanoindentation experiments. (3) With increasing temperature, the elastic modulus, hardness, and fracture toughness of granite exhibit progressive decreases, attributable to thermally induced damage. (4) Under varying stress conditions, elastic modulus and fracture toughness remain relatively stable, whereas hardness shows a significant decline with increasing equivalent stress. (5) Effective mitigation strategies for thermo-mechanical coupling effects, especially at elevated temperatures, are recommended to maintain the mechanical integrity of granite during the construction and operation of the Beishan URL and future HLW repositories. These results provide a solid scientific basis for the safe geological disposal of HLW in China, contributing to the sustainable development of nuclear energy and environmental protection.

In deep rock engineering, rocks are often in high water-pressure and high-stress environments. Under dynamic load disturbances such as blasting excavation, water pressure and in-situ stress influence the extent of rock damage, thereby affecting the propagation characteristics of stress waves. Using a self-developed testing system for stress wave propagation in rock under high water pressure and high axial static stress, the propagation characteristics of stress waves in red sandstone under hydro-mechanical coupling were investigated. Six water pressure levels and five axial static stress levels were designed to simulate the in-situ environment of engineering rock masses. Stress wave propagation tests were carried out on saturated red sandstone specimens to obtain stress wave waveforms under different working conditions. From the time-domain perspective of stress waves, the evolution laws of the transmission coefficient and propagation velocity with axial static stress and water pressure were analyzed, and corresponding empirical models were established. The results show that: at a given water pressure, both the propagation velocity and transmission coefficient of stress waves exhibit a Gaussian relationship with axial static stress; at a given axial static stress, both the transmission coefficient and propagation velocity first increase and then decrease with increasing water pressure, also following a Gaussian relationship. The transmission coefficient and propagation velocity show similar sensitivity to changes in axial static stress, whereas the transmission coefficient is more sensitive to water pressure than the propagation velocity.

To reveal the deformation and damage characteristics of coal under true three-dimensional cyclic excavation disturbances during coal mining, a series of raw coal mechanical tests was conducted under graded cyclic true triaxial stress conditions. The stress-strain behavior, strain sensitivity coefficients, and loading-unloading response ratios were analyzed. The experimental results indicate that during the true triaxial cyclic loading process, the principal strain corresponding to the direction of the cyclic principal stress dominates the deformation, with relatively larger deformation. When s₂ is large under cycle s₁, and when s₁ is large under cycle s₃, in both of the above conditions, e₂ will exhibit a strain reversal effect near the failure stage. Cyclic loading or unloading of s₂ may lead to instability and failure of coal, reflecting that the true triaxial ultimate strength curve is arc-shaped. The principal strain sensitivity coefficient corresponding to the cyclic principal stress is the highest and exhibits a synchronous trend with the volumetric strain sensitivity coefficient. When the graded cyclic loading of s₁ is applied, the unloading modulus is always greater than the loading modulus. As the number of cycles increases, the loading modulus first increases and then decreases, while the unloading modulus continuously decreases. The load-unload response ratio first drops sharply, then declines slowly, gradually approaching a value of 1, with the curve showing a noticeable upward trend near failure. The pattern is entirely opposite when graded cyclic unloading of s₃ is applied. As the number of graded cycles s₂ increases, the loading modulus and unloading modulus gradually approach each other. The experiments demonstrate that the strain reversal effect in e₂ under true triaxial cyclic loading and the subsequent deviation from 1 in the loading-unloading response ratio can serve as reference criteria for predicting coal failure.

The leaching solution readily migrates through high-permeability zones within the aquitard at in-situ leaching (ISL) uranium mining sites, leading to the diffusion of uranium and other contaminants into surrounding groundwater, which has become a critical bottleneck restricting the development of in-situ leaching uranium mining technology. Microbially induced calcium carbonate precipitation (MICP) exhibits effective cementation and permeability reduction in rock and soil. It can be used to seal high-permeability zones within the aquitard, but its standalone application often results in unsatisfactory sealing performance. Therefore, this study applies mesoporous silica (MS) synergistically with MICP to grout permeable sandstone from uranium mining areas and investigates its cementation and water-stopping performance. Through single-factor experiments, the effects of reaction time, grouting cycles, initial bacterial concentration (OD₆₀₀, the optical density measured at a wavelength of 600 nm), urea/Ca²⁺ molar ratio, and initial pH on the amount of calcium carbonate precipitation and the seepage reduction rate were analyzed. The sandstone before and after cementation was characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR), to reveal the mechanisms of permeability reduction by MICP-MS. The results show that the addition of MS increased both the calcium carbonate content and the seepage reduction rate of the cemented sandstone. With an MS addition amount of 4%, an initial bacterial OD₆₀₀ of 1.2, a urea/Ca²⁺ ratio of 1.5:1.0, and an initial pH of 7, after five grouting cycles, the MICP-MS treatment achieved a seepage reduction rate of 90.72%. Microscopic analysis revealed that MS is rich in various functional groups and acts as nucleation sites adsorbing Ca²⁺, which promotes the precipitation of calcium carbonate. Moreover, MS and calcium carbonate can form an MS-CaCO₃ composite cement that jointly fills pores and reduces the permeability coefficient of sandstone, effectively preventing the diffusion and migration of the leaching solution. These results provide reliable technical support for the green and sustainable development of in-situ leaching uranium mining.

Roughness is one of the key factors governing the shear mechanical behavior of pile-soil interfaces. Regular groove structure, as a geometrically controllable form of roughness, exerts a significant influence on the shear mechanical behavior and deformation characteristics of the interface. Therefore, a series of visualized direct shear tests was conducted on interfaces between regular grooved structural plates and silty clay using an improved visualized direct shear device. The shear mechanical properties of the interface under different groove widths, groove depths, and their combinations were investigated. Digital image correlation was employed to elucidate how groove parameters influence the shear deformation characteristics and mechanical mechanisms of the interface. The results show that, with increasing groove width and depth, the cohesion of the pile-silty clay interface first increases and then decreases, whereas the interface friction angle varies only slightly. The regular groove structure significantly enhances the interface shear strength. The shear strength increases first and then decreases with groove width, and increases first and then tends to stabilize with groove depth. An optimal groove width of 8 mm and an optimal groove depth of 4 mm were identified, at which the interface shear performance reaches its maximum. Increasing groove width leads to shear localization. Shear deformation gradually transitions from being controlled by a single passive zone to a zoned pattern, forming successively a passive zone, transition zone, and active zone along the shear direction. Under the optimal groove width, the passive zone reaches its maximum extent of 12.25 mm, with a vertical expansion height of 2.31 mm. The contribution of groove depth to interface shear strength exhibits a pronounced size effect. Under the optimal groove depth, the soil within the grooves is fully mobilized to participate in interface shearing, producing the most significant strengthening effect. Reasonable selection of grooved parameters is therefore crucial for fully mobilizing the shear resistance of pile–soil interfaces with regular grooved structures. The findings provide a theoretical basis for the rational selection and optimization design of surface structural parameters of threaded piles or ribbed piles in engineering.

To accurately describe the diffuse instability behavior of sand-fine mixtures under different loading paths, the influence of fines content on the evolution mechanism of stress increments was systematically investigated based on the H-model theory and the discrete element (DEM) strain probe analysis. The results indicate that the effect of fines content on the direction of stress increments is mainly concentrated in the initial shear stage, whereas its influence on the magnitude of the stress increments depends on the stress path and is independent of the current strain state. On this basis, the particle size ratio is further introduced, and an improved H-model comprehensively considering the effects of fines content and size ratio is established. By incorporating five parameters, this model describes the instability response of sand-fine mixtures under multi-factor coupling and different loading paths using only one set of parameters. Proportional strain loading tests and constant shear drained tests on sand-fine mixtures were simulated, and the results show that the predictions of the improved H-model are in good agreement with the laboratory test results, verifying that the model can effectively capture the coupled effects of fines content and size ratio on the instability characteristics of sand-fine mixtures under different loading conditions.

The soil-carrying effect is a unique overlying soil response mode in the construction of shallow-buried rectangular pipe jacking, a core risk source requiring key prevention and control in engineering, and a phased deformation response of overlying soil induced by the superposition and coupling of active and passive soil arching effects. To clarify the active-passive evolution law of the soil-carrying effect dominated by the over-excavation gap during pipe jacking and the influence characteristics of burial depth on it, the authors took the shallow-buried rectangular pipe jacking project of Sanyuanqiao as the prototype, proposed an active-passive progressive evolution model of overlying soil based on the over-excavation gap, and independently developed a scaled model test system for long-distance rectangular pipe jacking. Using transparent soil and digital image technologies, the authors carried out full-process transparent model tests of long-distance jacking under different shallow burial depths ranging from 0.30D to 0.90D (D is the width of the pipe), and systematically studied the active-passive state evolution, zoning formation law, long-distance accumulation characteristics and burial depth sensitivity of the soil-carrying effect dominated by the over-excavation gap. The results show that the over-excavation gap is a necessary prerequisite for the occurrence of the soil-carrying effect, and its spatiotemporal coupling with the jacking distance constitutes the macroscopic core mechanism of the effect. The soil-carrying effect exhibits a three-stage evolution characteristic of settlement zone, compensation zone and heaving zone, and evolves repeatedly under long-distance jacking, with the deformation amplitude of each event decreasing. The soil-carrying effect has high sensitivity to variations in burial depth: the overlying soil presents integral deformation in the shallow burial range of 0.30D–0.60D, and the shallower the burial depth, the more significant the deformation response; a decoupling phenomenon of deformation response between surface and deep soil exists in the range of 0.75D–0.90D. This study enriches the evolution mechanism of the soil-carrying effect in shallow-buried rectangular pipe jacking, and provides experimental support and theoretical basis for stratum disturbance control in shallow-buried rectangular pipe jacking construction and refined protection of surrounding buildings and structures.

To reveal the mechanical properties of grouted sandstone under incremental loading and to evaluate the reinforcement performance of sulfate aluminate cement (SAC), ultrafine cement (UFC), and epoxy resin (EPR), uniaxial cyclic loading–unloading tests were conducted. In combination with acoustic emission (AE), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) techniques, the mechanical response and pore structure characteristics of the grouted sandstone were quantitatively analyzed, and rock fracture precursors were identified. The results showed that: (1) Grouting reinforcement significantly improved the mechanical properties of fractured (F) sandstone. Compared with F specimens, the peak strength increased by 48.9%, 65.0%, and 72.8% for SAC, UFC, and EPR specimens, respectively; the secant modulus increased by 1.52, 1.84, and 1.84 GPa; and the peak strain increased by 0.10%, 0.13%, and 0.20%. EPR exhibited superior bonding and anti-decomposition properties, making it the optimal grouting material. (2) The Gaussian mixture model–support vector machine (GMM–SVM) classification method was suitable for incremental loading conditions. The proportions of shear cracks in F, SAC, UFC, and EPR specimens were 68.7%, 65.7%, 58.0%, and 70.1%, respectively, consistent with the shear-dominated macroscopic failure modes. (3) SAC and UFC materials increased pore complexity, whereas EPR grouting reduced it and effectively arrested crack propagation. (4) Under incremental loading, the window coefficient of variation outperformed the fusion index in capturing fracture precursor characteristics, demonstrating potential as a key early-warning indicator. The findings offer valuable guidance for the selection of grouting materials and the monitoring and early- warning strategies in complex stress zones of underground rock mass engineering.

Bentonite is a clay material dominated by montmorillonite, whose layered structure carries permanent negative charges due to isomorphic substitution. The layer charge is a key factor governing its swelling behavior. In this study, the coupled effects of layer charge and vertical stress on the one-dimensional swelling deformation characteristics of bentonite were systematically investigated through experimental tests and theoretical analysis. Sodium bentonite was used as the base material, and a series of reduced-charge bentonites with progressively decreasing layer charge were prepared using the lithium fixation method. One-dimensional swelling tests were then conducted under different vertical loading conditions. The results show that as the layer charge decreases, the swelling strain of bentonite is significantly reduced and the time required to reach swelling equilibrium is markedly shortened. Meanwhile, vertical loading exerts a pronounced inhibitory effect on swelling deformation, with increasing load leading to a lower swelling magnitude. Moreover, as the vertical load increases, the influence of layer charge on swelling deformation gradually diminishes. By adopting an intergranular stress that can reflect the physicochemical interactions between particles to simulate the above experimental results, it is found that the void ratio-stress relationships of bentonites with different layer charges converge onto a single curve. A single set of parameters can be used to simulate the swelling behavior of bentonite under the coupled effects of layer charge and vertical stress, providing a theoretical basis for the development of a unified chemo-mechanical coupling model.

Creep deformation of rockfill materials is a key factor affecting the long-term safety of high earth-rock dams, and may lead to face slab voids, cracking and failure of the seepage control system. Existing creep models are mostly established on the basis of single-stage loading creep tests, thus hardly reflecting the loading–creep coupling effect, and there is a lack of systematic investigation into the influence of stress unloading on subsequent creep behavior. To this end, multistage loading creep tests of rockfill materials considering unloading were carried out. The results show that the post-unloading creep behavior can be divided into a positive creep zone, a no-creep zone and a reverse creep zone according to the unloading magnitude: in the positive creep zone, the creep deformation gradually decreases with increasing unloading magnitude until approaching zero; in the no-creep zone there is almost no creep development; after large unloading, slight reverse creep may occur. Under the post-creep-unloading condition, almost no creep occurs over most of the unloading range. Based on the accumulation rule of hardening creep strain, the influence of stress history such as loading and unloading on subsequent creep behavior can be uniformly characterized, and its applicability is verified by complex loading–unloading stress path tests. This study provides experimental basis and theoretical support for improving the creep theory of rockfill materials and predicting the long-term deformation of high dams, and has important reference value for engineering practice.

During the excavation and unloading process of deep cross-strata roadways, the stiffness degradation of surrounding rock is a key factor inducing dynamic disasters. To reveal the coupling effect of loading rate on rock failure mechanisms under low- stiffness constraints, multi-rate uniaxial compression tests on sandstone under high- and low-stiffness conditions were conducted using a self-developed variable-stiffness testing system. The mechanical behaviors and the rate-effect mechanisms of the stress-strain curves of sandstone under different stiffness constraints were comparatively analyzed, with a primary focus on the instability failure characteristics and energy evolution laws of sandstone under low-stiffness constraints. The results indicate that: (1) Low-stiffness constraints alter the conventional rate-dependent behavior of rock, with the transient compensatory effect of elastic energy accumulated in the system dominating the failure process, thereby enhancing the sensitivity of mechanical parameters, such as peak strength, to the loading rate. (2) With the increase in loading rate, the rock failure mode transitions from progressive step-like fracturing to transient instability at 0.15 mm/min, leading to intensified macroscopic tensile failure and an elevated proportion of mesoscopic tensile events. (3) The energy evolution law controlled by stiffness-rate coupling is elucidated. The low stiffness determines the macroscopic baseline for the forced release of post-peak elastic energy, while the increase in loading rate dynamically alters the post-peak energy dissipation path, driving the transition of energy release from step-wise dissipation to transient accumulation. The research findings reveal the essence of dynamic instability in rock masses under deep low-stiffness environments, providing theoretical support for the prevention and control of dynamic disasters in deep engineering.

Soil-bentonite (SB) cutoff wall is commonly employed as a vertical barrier to prevent further leakage of landfill leachates. With this engineering background, based on the multi-solute transport framework, this study presents a theoretical model that can be used to evaluate the barrier performance of the SB cutoff wall considering the effects of prior contamination and source remediation. Three solutes are considered in this model, among which Na⁺ and Ca²⁺ are selected as non-characteristic pollutants, and a single organic pollutant is selected as the characteristic pollutant. Afterwards, the finite difference method is adopted to solve the model, and its rationality is verified by three comparative studies. Finally, taking toluene as the characteristic pollutant, the effects of different factors on the wall’s barrier performance are evaluated using the defined breakthrough time tB. The results show that an increase in the prior contamination time tP decreases tB, and the reduction rate of tB may reach 38.8% when tP is 2 a. However, the increase in the transition layer thickness lu has the opposite effect. An increase in the source concentration reduction parameter (S and a decrease in the source remediation initiation time tS both contribute to prolonging tB. Moreover, when S is large (e.g., greater than 0.61 a⁻¹), the wall may not be broken through by organic pollutants. Neglecting the presence of Na⁺ and Ca²⁺ may overestimate the service time of the SB cutoff wall by more than 47.0% compared with considering their presence. Under the same engineering condition, an increase in bentonite content increases the thickness of the bound-water film on the surface of soil-bentonite, which causes an increase in tB. In engineering practice, the SB cutoff wall can be designed by comprehensively considering the internal and external factors as well as the construction cost and service life requirements. Overall, this work can provide scientific guidance for the application of SB cutoff walls in anti-seepage and containment engineering of landfills.

To investigate the stability of roof-pillar systems in deep goaf groups, a three-dimensional mechanical model of the roof-pillar system was established that accounts for the high in-situ stress and lateral stress. Based on the accelerated creep behavior of rock pillars, a second-order dynamic model incorporating time-varying stiffness and damping degradation was developed. Catastrophe theory was introduced to propose an instability catastrophe criterion for the roof-pillar system, and a normalized sensitivity analysis was conducted to reveal the differences in the effects of various influencing factors. The results indicate that the pillar support area ratio, pillar elastic modulus, and uniformly distributed roof load have significant effects on system stability. The proposed model was verified against a deep iron mine case. Within two months after excavation completion, the theoretically predicted roof displacement was 2.5 mm, close to the monitored value of 2.1 mm. The model predicted that the system would remain stable for 15 months, with the roof boundary conditions remaining intact when instability occurred. This study provides a theoretical basis for stability evaluation and disaster early warning of deep goaf groups.

Vegetation roots can effectively enhance the shear strength of near-surface soils, and root reinforcement has become an important measure to improve shallow slope stability in ecological slope protection engineering. This study employs the discrete element method to construct a refined three-dimensional root system model and investigate the mesoscopic mechanisms governing the evolution of shear behavior at the root-soil interface. The influence of different inclined shear angles (5°, 10°, 15°) on the shear mechanical response of root-reinforced soil is systematically examined, and, under three levels of vertical stress, the evolution of shear strength, the shear resistance contribution of different hierarchical roots, and the distribution of taproot tensile stress are analyzed. The results show that the shear strength of root-reinforced soil increases significantly with vertical stress, shear angle, and root area ratio on the shear plane. The confinement provided by lateral and fibrous roots contributes most to shear resistance, and their relative roles adjust with changes in shear angle. The axial tensile stress in the taproot develops in a staged manner with increasing vertical stress and shear angle and is most effectively mobilized under a shear angle of 10°. This study elucidates the reinforcement mechanisms of hierarchical root systems under inclined shear and provides a reference for the mechanical design of ecological slope protection.

The safety of the lining structure and the air tightness of the underground gas storage cavern under cyclic high internal pressure are the dual challenges faced in the construction of compressed air energy storage (CAES) caverns, and are the key factors determining the success or failure of CAES power stations. The purpose of underground caverns serving as CAES gas storage containers is to fully utilize the bearing capacity of the surrounding rock. A CAES gas storage cavern consists of a sealing layer, a lining system, and the surrounding rock. The surrounding rock should be both rigid and tough, the lining both flexible and ductile, and the sealing layer flexible and durable. The "flexibility" of the sealing layer and the lining may refer to the flexibility of the material itself (e.g., polymer flexible sealing layer and flexible concrete lining), or to the adoption of flexible or ductile structures (e.g., crack-control design and deliberate crack-inducing design to enhance the toughness of reinforced concrete lining, and profiled steel lining to increase the flexibility of the steel-lining sealing layer). This paper reviews the design status and research progress of sealing and lining structures for CAES caverns and offers prospects for future development.

To reveal the evolution of static stability of upstream tailings dams under the combined effects of construction rate, fine-grained interlayers, and drainage facilities, this paper employs FLAC3D, integrating the Duncan-Chang constitutive model with the Van Genuchten-Mualem seepage model, to simulate the stability response of the dam during incremental construction. The results indicate that the landslide mode of the dam evolves through three stages: the unsaturated zone stage, the partially saturated zone stage, and the saturated zone stage. The shape of the most dangerous sliding surface is governed by the internal structure: it remains circular in homogeneous dams, whereas in dams containing fine-grained interlayers, it gradually transitions from circular to a non-circular shape controlled by the interlayers. The horizontal displacement at the crest of the starter dam exhibits three stages: initial deformation, uniform deformation, and accelerated deformation. The accelerated deformation stage is triggered by fine-grained interlayers and can be effectively suppressed by improving drainage. The safety factor evolution follows a two-stage pattern: the unsaturated-partially saturated zone landslide stage and the saturated zone landslide stage. The controlling effect of fine-grained interlayers on the sliding surface morphology only becomes apparent during the saturated zone landslide stage. The findings of this paper can provide a reference for the safety management of upstream tailings dams and help reduce the risk of static instability.

The pressure-cast-in-situ fluid solidified soil pile (PFSSP) is a new type of flexible pile developed by the authors. Compared with traditional cement mixing piles, it has the advantages of stable pile quality and high single-pile bearing capacity. To investigate the bearing characteristics of the PFSSP composite foundation, a plate load test was carried out on the PFSSP composite foundation, and a three-dimensional numerical model of the PFSSP composite foundation was established. The rationality of the numerical calculation results was verified using the field plate load test results, and the influences of the expansion ratio (defined as the ratio of the expanded body diameter to the upper pile diameter), the position of the expanded body, and the lower pile diameter on the bearing characteristics of the PFSSP composite foundation were analyzed based on the numerical calculation results. The research results show that the PFSSP composite foundation can give full play to the core bearing role of the pile body and effectively utilize the bearing potential of the soil mass. Considering the rationality of load bearing, construction feasibility and economic efficiency, the expansion ratio of the PFSSP is preferably 1.4 to 1.5, the optimal position of the expanded body is in the range of 2 to 4 times the upper pile diameter, and the optimal range of the lower pile diameter is 300 mm to 350 mm. The research results can provide a reference for the optimal design of the PFSSP composite foundation.

Time-dependent deformation of surrounding rock in soft rock tunnels is prone to induce distresses such as floor heave and structural cracking, posing a severe threat to driving safety. The resilience evaluation of support structures holds great significance for the prevention and control of distresses in soft rock tunnels during the operation period. However, existing resilience evaluation methods are mostly oriented towards sudden disasters and are difficult to apply to the resilience assessment of soft rock tunnels under the action of long-term time-dependent deformation. To address this issue, this study first analyzes the characteristics of time-dependent deformation distresses in soft rock tunnels, establishes a corresponding performance evaluation index system for support structures, proposes a multi-index evaluation method for structural performance based on the improved criteria importance through intercriteria correlation objective weighting method, and constructs a resilience calculation method for support structures under the action of time-dependent deformation. The proposed resilience evaluation method for time-dependent distresses is applied to the analysis of floor heave distress in a typical soft rock tunnel. The results indicate that the disaster resilience of tunnel floor heave distress decreases continuously with the increase of time-dependent deformation, and the decreasing rate slows down gradually over time, with a variation trend similar to that of time-dependent deformation. The influence weight of longitudinal smoothness of track on the disaster resilience of floor heave distress approaches 80%, serving as the primary controlling factor, while the influence weight of the stress state of the support structure is merely 1.4%. Therefore, in the resilience evaluation of floor heave distress, priority should be given to the deformation monitoring of support structures, and the stress monitoring of structures can be appropriately reduced to lower the monitoring cost.

Anti-slide pile, as a common structure for slope reinforcement, has been widely used around the world. In traditional anti-slide pile design, only the factor of safety is used to evaluate the reinforcement effectiveness, which is not able to account for the effect of inherent spatial variability of soil parameters and economic costs on the anti-slide pile design. To this end, a bi-objective weighted optimization design method for anti-slide pile is proposed considering the spatial variability of soil parameters. This method regards pile diameter, pile length, pile spacing, and pile location as design parameters. By coupling the reliability analysis of pile-reinforced slopes with Pareto optimization theory, the best design parameters are obtained through maximizing reinforcement effectiveness and minimizing economic costs. The validity of the proposed method is illustrated by a case study of a single-row pile-reinforced slope. The results indicate that this method can effectively balance the conflict between safety and cost, yielding the best trade-off solution. Engineers can also determine different safety and economic weighting factors based on engineering grade and failure consequence, in order to select a safer or more economical design solution on the Pareto front. Under the random field condition, the design length of anti-slide pile is larger than that under the deterministic condition, and the best reinforcement effect is achieved when the pile is located near the middle of the slope. The bending moment of the pile body and the displacement at the pile top may be significantly underestimated under the deterministic condition, leading to a high-risk design and misleading the operational monitoring.

The material constitutive model is the basis of numerical analysis in geotechnical mechanics. Phenomenological constitutive models, represented by elastoplastic models, are the mainstream of geotechnical constitutive research. In recent years, data-driven methods such as neural networks have increasingly become an important means of constitutive modeling owing to their strong nonlinear fitting capability. However, conventional data-driven models, lacking prior physical knowledge, are prone to poor generalization and physical inconsistency. This paper proposes an improved neural network-based constitutive modeling method that explicitly incorporates mechanical mechanisms including thermodynamic consistency and plastic dissipation stability within the elastoplastic mechanics framework. Taking the von Mises model and the modified Cam-clay model as examples, diverse stress paths are generated by Gaussian process to construct training sets, and the performances of purely data-driven and mechanics-constrained models are systematically compared. The results show that, with the introduction of mechanical constraints, the prediction accuracy and stability of the model under unseen paths are significantly improved. The engineering applicability and generalization potential of the proposed method are verified by finite element integration tests.

Physics-informed neural networks (PINNs) have attracted considerable attention in geotechnical engineering as an artificial intelligence approach for inverting soil and rock parameters by integrating measurement data with physical laws. However, due to the highly nonlinear mapping between parameters and the loss function, PINNs often fail in complex, high-dimensional parameter inversion problems. To enhance the generalization capability of PINNs, a damped physics-informed neural network (dPINN) is developed by improving the conventional PINN, and is applied to invert the hydraulic conductivity field of geologic media—spatially following a generalized sub-Gaussian distribution—in two cases: a two-dimensional steady-state saturated groundwater flow (Case 1) and a one-dimensional transient soil infiltration (Case 2). The results show that: (i) the dPINN can effectively invert the conductivity field in both cases, reducing the relative L₂-norm error (Y) in Case 1 by 29% compared with the conventional PINN; (ii) as the non-Gaussianity of the conductivity field decreases, Y in Case 1 decreases from 0.88 to 0.71; and (iii) the sensitivity of inversion accuracy to the weights of different physical constraints ranks as governing equation > Dirichlet boundary > Neumann boundary. The proposed method and findings provide a useful reference for geotechnical numerical modeling and parameter inversion.

Based on the wave function expansion method and the cylindrical wave–plane wave conversion technique, this study investigates the scattering of plane SH waves by a circular cavity in an overburden layer overlying an elastic half-space. A series solution for the dynamic response is derived. The solution accuracy is ensured by strictly satisfying the stress-free condition on the cavity surface and the continuity conditions of displacement and stress at the layer interfaces. Its validity is further verified by comparing the results of a degenerate model with a classical solution. A systematic parameter analysis is conducted to examine the influence of the modulus ratio between the overburden layer and the half-space, overburden layer thickness, cavity burial depth, dimensionless frequency, and incident angle. The results indicate that as the modulus ratio increases, the displacement amplitude decreases, whereas the shear stress amplitude increases. The overburden thickness causes fluctuations in response amplitude due to the periodicity of the transmission coefficient, although the distribution pattern changes little. Shallower burial depths result in more significant surface responses of the cavity. An increase in dimensionless frequency intensifies circumferential fluctuations and raises the overall amplitude, but the displacement at the cavity crown diminishes due to weakened diffraction. The incident angle substantially alters the symmetry and amplitude of the response, with oblique incidence yielding higher amplitudes.

Under prolonged shear, granular systems reach a critical state with constant macroscopic volume fraction and shear stress, which is commonly described and modeled by the macroscopic critical state theory. However, the mesoscopic origin of the critical state of granular materials remains to be further investigated. Biaxial shear tests were carried out on granular specimens with different initial densities by the discrete element method, and a dynamic evolution analysis method for contact networks based on persistent homology was introduced, which effectively overcomes the difficulty of quantitative characterization caused by the high-dimensional heterogeneity of contact networks. Based on the evolution law of network topology during spatial filtration, the highly heterogeneous composition of the contact network was quantitatively analyzed, and the optimal partition threshold for strong and weak contact systems was proposed. It is found that this threshold is mainly determined by the current shear state of the system and has little correlation with the initial density. Although the contact networks of specimens with different initial densities differ significantly at the early stage of shearing, they all evolve towards the same "mesoscopic critical state" as shearing proceeds, characterized by constant topological structural properties and dynamic evolution rate; moreover, this state is unique and independent of the initial density. It is revealed that the evolution of the contact network towards the critical topological structure and dynamic behavior is the mesoscopic topological origin of the macroscopic critical state of granular systems.

Plain earth dams are frequently constructed on soft soil foundations, and their consolidation process is crucial to engineering safety. Traditional finite element methods have limitations such as high computational overhead and mesh dependency when dealing with complex geometric boundaries and heterogeneous soil layers. This paper proposes an intelligent prediction method for pore water pressure evolution during the consolidation process of plain earth dams based on physics-informed neural networks (PINN). By embedding Terzaghi’s two-dimensional consolidation equation into the neural network architecture and combining automatic differentiation technology, a physics-driven simulation of PWP evolution is achieved. Aiming at the complex geometric boundaries of the Erwangzhuang Reservoir capacity expansion project, strategies such as boundary extraction and classification, masked stratified sampling, and a two-stage joint training approach are proposed, which significantly improve the model’s adaptability to dynamic computational domains and its training stability. The results show that, even with only sparse monitoring data, the PINN model can still accurately simulate the spatial-temporal evolution process of pore water pressure. The coefficient of determination (R2) is greater than 0.83, the root mean square error (RMSE) is less than 0.33 kPa, and the mean absolute error (MAE) is less than 0.19 kPa. Its performance is superior to that of purely data-driven neural networks, validating the feasibility and effectiveness of this method in practical engineering. This study provides a new, efficient, and reliable method for the consolidation analysis of plain earth dams.

Deep-sea sediments serve as essential bearing foundations for deep-sea engineering. However, obtaining deep-sea samples is difficult and costly, which makes it challenging to support large-scale laboratory geotechnical model tests. This study proposes a laboratory method for preparing simulated deep-sea clay based on similarity evaluation. Firstly, a small amount of original deep-sea soil is obtained, and its physical and mechanical properties are measured. Several physical and mechanical properties are then selected as similarity evaluation indices. Secondly, based on the mineral composition, grain group composition, and biological components of the original deep-sea soil, easily accessible materials are chosen as raw components. Using an improved slurry consolidation apparatus and an orthogonal experimental design, a series of samples with different material proportions is prepared. The entropy weight method is introduced to calculate the comprehensive scores of the samples, and range analysis is used to optimize the mixture design and identify key factors influencing similarity. Finally, deviation testing is conducted to verify the feasibility and effectiveness of the optimal mix ratio. Taking deep-sea clay from a water depth of 3 200 m in the northern South China Sea as the simulation target, simulation preparation tests are carried out using the proposed method. The feasibility and effectiveness of the method are further validated through dynamic mechanical property tests. The proposed approach provides a viable solution for the batch preparation of samples for large-scale indoor geotechnical model tests in deep-sea engineering, and also offers a reference for the simulation preparation of other deep-sea sediments.