The initial anisotropy resulting from particle shape and granular arrangement significantly influences the mechanical behaviors of cemented geo-materials. To establish an anisotropic strength criterion for cemented geo-materials that incorporates micromechanical mechanisms, we utilize regularly arranged elliptical particle assemblies. By employing a micro-analytical model, we develop an equivalent lattice model for these assemblies, assign particle contact properties to the corresponding lattice beams, and apply a size-dependent nonlinear yield criterion to describe beam breakages. Through mechanical analysis of the instability state of the representative volume element, we propose macroscopic strength and corresponding strength parameters expressed in terms of microscopic parameters (particle shape parameters, contact parameters) and the tilting angle. The correctness of the analytical solution is verified through numerical simulations based on the discrete element method. The results demonstrate that the proposed strength analytical formula can effectively reflect the influence of initial anisotropy on the mechanical properties of cemented geo-materials. The macro-micro quantitative correlation analytical solution reveals the quantitative influence of initial anisotropy caused by particle shape and regular arrangement, as well as inter-particle contact characteristics, on macroscopic mechanical behaviors.

With the increase of global temperature, the ice crystals at the warm frozen soil-concrete interface are easy to melt, resulting in the decrease of ice cementation force, which in turn leads to the deterioration of interface strength and affects the stability of infrastructure. Pseudomonas syringae (P. syringae) can induce the orderly arrangement of water molecules to promote the growth of ice crystals at elevated temperatures. However, research regarding its application in promoting ice film formation at the warm frozen soil-concrete interface and further enhance the interface strength remains notably absent. Therefore, in this paper, nuclear magnetic resonance and direct shear tests were carried out to study the effects of P. syringae concentrations (0, 1 g/L) on the shear stress-horizontal displacement curve, shear strength and strength index of warm frozen soil-concrete interface at 0,−0.5 ℃ and−1 ℃. After the addition of P. syringae, the ice content of frozen soil increased by 38 %, the interfacial cohesion improved by 29.1 %, the interfacial strength increased by 19 %, and the residual strength enhanced by 7 %. Based on the Mohr-Coulomb criterion and the generalized Darcy 's law, the strengthening mechanism of the warm frozen soil-concrete interface under the action of P. syringae can be summarized as follows: the enrichment of P. syringae occurs due to the migration of water towards the interface, which subsequently induces the formation of ice crystals at relatively elevated temperatures. These ice crystals then then fills the pores, ultimately leading to interface interlocking enhancement and a significant improvement in interface strength. This study initially unveils the potential of P. syringae in augmenting the strength of warm frozen soil-concrete interface, thereby offering theoretical underpinnings for the application of P. syringae in the design and construction of infrastructure in warm frozen soil areas.

The prediction methods for the collapsibility coefficient of loess are predominantly based on regression analysis, but they are significantly influenced by the regional characteristics of loess, leading to insufficient prediction accuracy. Furthermore, existing machine learning prediction methods have limitations in interpretability. Focusing on the loess in the Longxi region, five pivotal influencing factors, namely, density, saturation, self-weight stress, liquid limit, and internal friction angle, were identified through correlation and cluster analyses. Subsequently, prediction models for the loess collapsibility coefficient were constructed using extreme gradient boosting (XGBoost), random forest (RF), support vector machine (SVM), and regression analysis. Additionally, an interpretability analysis of the prediction outcomes was performed using the Shapley additive explanations (SHAP) technique. The results show that the correlation coefficients between the collapsibility coefficient of Longxi loess and various indices such as density, dry density, void ratio, saturation, and internal friction angle range from 0.63 to 0.90, indicating extremely strong or strong correlations. Both the XGBoost and RF models demonstrate a prediction accuracy exceeding 90% for the collapsibility coefficient and collapsibility grade, thereby outperforming the SVM model and conventional regression methods. The SHAP analysis reveals that loess with a density less than 1.44 g/cm³ has a higher probability of collapsibility, while loess with a saturation greater than 29.0% has a relatively lower collapsibility grade. Moreover, loess under high saturation and high self-weight stress conditions exhibits weaker collapsibility tendency and lower collapsibility grade. The findings provide a theoretical reference for loess engineering construction in the Longxi region.

Water outbursts represent one of the primary geological hazards in underground engineering. Traditional grouting materials exhibit poor retention rates and weak erosion resistance, resulting in inadequate sealing effectiveness. To address this, the team independently developed a modified cement-based magnetic grouting material. Magnetic adsorption properties and SEM analyses were conducted to investigate the influence of magnetic powder dosage on magnetic adsorption performance. The study revealed the cementitious hardening mechanism at the microscopic level, where additives synergistically regulate cement particle dispersion and accelerate hydration processes. Through pipe-type fissure water ingress sealing tests, the pressure variation pattern—the "gradual increase-abrupt surge-sudden drop-stabilization" time-varying pattern—under different magnetic powder dosages, sealing section lengths, and magnetic induction intensities was systematically investigated. Results indicate that increasing magnetic induction intensity from 0.289 5 T to 0.526 5 T enhances magnetic adsorption performance by 28.12%; under identical conditions, raising magnetic induction intensity from 0.412 3 T to 0.526 5 T increases sealing water pressure by 24.7%; and increasing the magnetic powder content from 20% to 40% boosts the plugging water pressure by 38.5%. By coupling the magnetic field force with the Navier-Stokes (N-S) equation, a prediction model for water outburst plugging under magnetic field influence was established. The theoretical peak plugging pressure value exhibited an error of less than 9% compared to the experimental value. This model provides valuable guidance for refining the theory and engineering application of magnetic slurries.

To explore the bearing mechanism and failure mode of the rock stratum at the end of pile row crossing over underlying karst caves, laboratory model tests of pile row crossing an underlying karst cave were carried out. The ultimate bearing capacity and failure modes of the rock layer at the pile end were obtained for various pile row configurations. Based on the test phenomena and existing research, the failure modes of pile row overlying an underlying karst cave were proposed. A simplified method for calculating the ultimate bearing capacity of the rock layer beneath a single pile toe was developed using the limit equilibrium method. Furthermore, incorporating the test results, calculation methods were proposed for determining the ultimate bearing capacity of the rock layer beneath the toes of double-pile, triple-pile, and quadruple-pile rows overlying an underlying karst cave. The calculated results agreed well with the experimental values, validating the rationality of the proposed methods. Finally, the influences of roof thickness h and load eccentricity e on the bearing capacity reduction factor for pile row overlying an underlying karst cave were analyzed. Findings reveals that:1) Pile row foundations superimposed on underlying karst caves demonstrate four distinct failure modes, contingent upon the roof thickness, load eccentricity distance, and pile spacing. These modes encompass punching failure of the cave roof, composite punching failure involving the cave roof, eccentric load-induced punching failure, and general shear failure of the rock foundation. 2) When the eccentricity distance is small (1d, 2d, where d denotes diameter) and the roof thickness is thin, the bearing capacity reduction factor increases approximately linearly with roof thickness. Upon reaching a specific thickness, the variation trend becomes essentially consistent with that observed when the eccentricity distance is e≥3d. 3) The ultimate bearing capacity of triple-pile and quadruple-pile row overlying an underlying karst cave approximates that of intact bedrock when the roof thickness h= 4.3d. When h＞ 4.3d, the ultimate bearing capacity of triple-pile and quadruple-pile rows becomes independent of the load position, and the rock mass beneath the pile toes consistently undergoes overall shear failure.

To investigate the superposition effect of three-dimensional compressive stress on the longitudinal wave velocity of rocks and improve the testing precision of the rock mass integrity index, this study takes sandstone-like materials as the research object and measures the evolution law of axial and transverse longitudinal wave velocities in specimens under compressive stress. The internal crack evolution process is qualitatively characterized by the crack volume strain, revealing the physical essence of the longitudinal wave velocity variations. Based on the principles of the acoustic-elastic effect, a correction model for the longitudinal wave velocity of rock blocks under the coupling effect of three-dimensional principal stresses is established, and a method for correcting the rock mass integrity index under the condition of a corrected three-dimensional in-situ stress field is obtained. The results indicate that the evolution of the longitudinal wave velocity, measured both axially and transversely, corresponds to the four distinct stages of rock mass failure. The corresponding variations in the longitudinal wave velocity across different stages can be attributed to three primary factors: micro-crack closure and initiation altering wave propagation paths, rock mass compaction enhancing stiffness, and the marked anisotropy of newly generated micro-cracks. The proposed correction model for the longitudinal wave velocity and the associated method for revising the rock mass integrity index demonstrate broad engineering applicability. This approach significantly enhances the measurement precision of the rock mass integrity index, thereby facilitating a more refined classification of rock mass quality.

Compressive fault fracture zones are characterized by their dense structures, weak cementation, and low permeability. Within these zones, fine clay particle constituents, which contain a high proportion of clay minerals, are susceptible to softening and argillization upon contact with water, thereby playing a crucial role in the permeability-deformation failure mechanism of the entire structure and long-term seepage stability of reservoir areas. This study takes stone content ratio S and Talbot index n as key parameters, and reveals the dominant role of fine clay particle content (p) in the permeability evolution characteristics of fault fracture zones through systematic laboratory permeability tests. Experimental results indicate that: 1) The initial permeability coefficient k₀ exhibits a negative exponential relationship with fine clay particle content, where increased fine clay particle content can effectively reduce permeability.2) Fine clay particle content significantly controls the formation and evolution of threshold pressure gradient: at low content levels, it conforms to Darcy’s law (approximately non-viscous), and as p increases, it shows a linear growth (2.5%＜p＜20%) and an exponential growth (p≥20%) in turn. 3) Critical and failure hydraulic gradients are regulated by the coupling of p and S, with sensitivity of gradient to p changes diminishing at high stone content ratios (S=60%). 4) Seepage failure modes undergo systematic transformation with increasing p: it shifts progressively from piping type (p≤2.5%) to transitional type (2.5%＜p＜20%), and ultimately evolves into soil flow type (p≥20%); concurrently, post-failure phenomena manifest as three modes: progressive penetration, central cavity formation, and concentrated failure. This study quantitatively elucidates the evolution law of the entire permeability-deformation process dominated by fine clay particle content, providing important theoretical basis for engineering disaster prevention and control in compressive dense fault fracture zones.

After reservoir impoundment, the frequency of medium-low intensity earthquakes in and around the reservoir area increases, and the landslide-prone zone expands. To reveal the influence of dynamic load on the mechanical properties of slope rock mass, typical limestone in the Baihetan Reservoir area was taken as the research object, and cyclic shear tests with different dynamic load amplitude ratios were carried out to analyze the degradation laws and mechanisms of joint mechanical properties under saturated state. The results show that: 1) Under cyclic dynamic shear with different amplitudes, the peak shear strength, residual shear strength and pre-peak shear stiffness of joints all show linear degradation characteristics. 2) Considering the influence of joint roughness coefficient on shear strength, the JRC-JCS model (joint roughness coefficient-joint wall compressive strength) is introduced to verify the test data, and the model is modified based on the degradation effect of cyclic shear on joint wall strength. After modification, the error between the calculated value and the test value is reduced to less than 5%. 3) The greater the cyclic disturbance amplitude, the more significant the damage to rock and joint surface. The continuous degradation of bank slope structural planes and rock mass damage accumulation in the reservoir area need to be focused on. The research results can provide a reference for analyzing the mechanical properties of reservoir slopes under the action of medium-low intensity induced earthquakes.

The deformation behavior of fractured rock masses is often a key factor causing instability of engineering rock masses and frequent geological disasters. The complex changes in the load acting on engineering rock masses can trigger and alter the mechanical response processes such as deformation and fracture of the rock masses. This study employs physical simulation techniques to replicate the behavior of real rock masses through the use of rock-like models. Specifically, single-fracture rock-like specimens with consistent characteristics are fabricated utilizing river sand, cement, gypsum, and putty powder. Uniaxial compression tests are subsequently conducted on these specimens to examine the impact of loading rate on their deformation behavior. The primary focus lies on the sliding deformation patterns exhibited by the media on either side of the fractures, as well as the fracture behaviors associated with the pre-existing fractures. To monitor the deformation evolution processes both internally and externally within the models, embedded strain rosettes and digital image technology are concurrently employed. This approach facilitates an exploration of the influence of loading rate on the deformation characteristics at the fracture tips and the fracture behaviors observed on the model surface. The results show that: (1) With the increase of loading rate, the failure mode of the model transforms from ductile to brittle, reflecting the differences in the adjustment mode of rock mass bearing structure under different loading rates. (2) The initiation time of strain localization is independent of the rate, and as the loading rate increases, the strain deflection angle of the tension and compression stress zones in the model changes from asynchronous oscillation to synchronous oscillation. (3) At low loading rates, the failure mode of the model is stable. As the loading rate increases, the failure mode becomes more complex, and the surface crack density increases. When the loading rate exceeds a certain threshold, the failure mode of the model changes to "X-shaped" shear failure. (4) There is a significant correlation between the sliding rate of the fracture and the deflection angle of the principal strain at the end, reflecting the coupling effect of rock mass damage and strain field evolution under Griffith's criterion.

Currently, the bearing capacity design of prestressed steel anchor pipe-anchor cable composite structures often neglects the mechanical properties of the four constituent materials—cable, grout, steel pipe, and surrounding rock—as well as the interfacial behaviors among them, thereby resulting in theoretical research lagging behind engineering practice. To elucidate the effects of various parameters on the bearing capacity and failure mechanisms of these composite structures, four full-scale experimental tests were conducted, supplemented by numerical simulations. The analyses focused on key parameters including bearing capacity, failure modes, and strain distribution at different interfaces. The results indicate that: 1) The bearing capacity and strain of the composite structure are predominantly governed by the number of steel strands, while the influence of steel pipe diameter is comparatively minor. Within the tested range, adding one steel strand increases the bearing capacity of the steel anchor pipe-cable composite structure by an average of 276 kN. 2) With an increasing number of steel strands, the failure mode transitions from local strand rupture to simultaneous rupture of multiple strands, with no other failure modes observed, indicating that the interface bond strengths all surpass the ultimate tensile strength of the steel strands. 3) The strain distribution patterns at the interfaces between the steel pipe and grout, as well as between the grout and surrounding rock, generally demonstrate structural consistency; however, the latter exhibits a discernible "lag" phenomenon in comparison to the former. 4) Increase in the grout’s elastic modulus, anchorage length, and steel pipe diameter can all effectively reduce the deformation of the corresponding materials.

To enhance the predictive precision of rock strength using the true-triaxial Hoek-Brown criterion and to further broaden its potential applications in deep underground engineering, this study proposes an improved true-triaxial strength criterion. This criterion integrates both the critical confining pressure effect observed under conventional triaxial conditions and the intermediate principal stress effect inherent in true-triaxial stress states. On the basis of the modified Hoek-Brown criterion considering the critical confining pressure, the intermediate principal stress coefficient is introduced via the weighted averaging method, and the stress substitution method is adopted to establish the improved true-triaxial strength criterion composed of combined curved segments and linear segments. The research results show that when the intermediate principal stress (σ₂) exceeds its critical value, the relationship between the parameters σ₁ and σ₂ changes from nonlinear to linear, and the intermediate principal stress becomes the dominant factor to control the rock strength. A comparative analysis conducted against the Priest criterion, Zhang-Zhu criterion and Li criterion reveals that the proposed improved criterion attains the lowest average value of mean absolute error (MAE) of 4.946 5% in the strength prediction of ten types of rocks. It is verified that the novel criterion can remarkably enhance the prediction precision of rock strength under complex stress conditions. Moreover, the established criterion demonstrates favorable applicability and exhibits promising potential for engineering applications in the strength assessment of deep rock mass projects and the quantitative determination of the critical effect exerted by the intermediate principal stress.

 To explore the influence of osmotic suction on the compression, yield, and critical state characteristics of unsaturated loess under three‑dimensional stress conditions, isotropic compression tests and constant p & constant b shear tests were conducted on loess with different pore water salinities by means of a suction‑controlled unsaturated true triaxial apparatus. The results show that the isotropic compression curve gradually moves down with the increase of osmotic suction, and the yield stress shows a decreasing trend. The shear strength decreases with the increase of b value and increases with the increase of osmotic suction. Under different b values, the critical state line in the p-q plane can be normalized to the critical state line of saturated loess by using the effective net mean stress, and the slope M increases with the increase of osmotic suction. The plastic potential surfaces in the meridian plane are elliptical. In the meridian plane, the plastic potential surfaces exhibit an elliptical shape. As the osmotic suction escalates, the major axis progressively diminishes in length, whereas the minor axis experiences an elongation. The critical state line in the e-lgp plane (e is the void ratio of unsaturated soil) exhibits an upward shift as osmotic suction increases, accompanied by a gradual reduction in the slopes denoted by λ₀, λ₁. The ratio of the critical state void ratio of unsaturated loess to that of saturated loess, denoted as e/e_s, exhibits a normalized relationship with the gas saturation (1−S_r, S_r is the degree of saturation of soil in the critical state). Furthermore, by incorporating the osmotic suction π , a three-dimensional predictive model is developed for determining the critical state void ratio of unsaturated saline loess.

The seismic response acceleration within reinforced slopes directly affects their anti-seismic characteristics and serves as a key parameter in seismic design. Current research on horizontal response acceleration in reinforced slopes primarily focuses on unidirectional seismic action, with limited consideration of bidirectional seismic effects, particularly for multi-tiered reinforced slopes. To address this, two sets of shaking table model tests were conducted on multi-tiered slopes subjected to varying seismic excitations. The results demonstrate that, under bidirectional seismic excitation, the amplification characteristics of horizontal and vertical accelerations differ significantly: the horizontal amplification is more pronounced compared to its vertical counterpart, and the synchronization between accelerations in two directions diminishes with increasing loading amplitude. The phase difference between horizontal response acceleration and input acceleration exhibits a decreasing trend from the slope surface toward the interior, as well as from the crest to the base, with the maximum phase difference under bidirectional seismic excitations being approximately double that observed under unidirectional conditions. The horizontal acceleration amplification factor exhibits higher values under bidirectional seismic excitation compared to unidirectional excitation, particularly within the third-tier reinforced slope when the input acceleration surpasses 0.4g. The pseudo-static method can effectively predict design values of horizontal response acceleration under different seismic directions, but it underestimates the acting height of the horizontal response acceleration.

The development of underground dissolution leads to the formation of numerous cavities in limestone, thereby affecting the stability of karst mountain. Conventional compression tests were performed on rocks with different hole numbers and diameters to investigate the peak strength, crack damage behavior, energy characteristics and failure modes under different confining pressures (σ₃) and dissolution rates (η). The results indicate that the uniaxial compressive strength and crack damage stress (σ_cd) of holed limestone are independent of the dissolution rate (η). Under triaxial compression, the peak strength of holed limestone can be described by a linear Mohr-Coulomb criterion. The cohesion (c) and crack damage ratio (σ_cd /σ_p) increase with the increase of dissolution rate (η), with the maximum increases being 14.04% and 14.1%, respectively. The peak strength (σ_p), frictional angle (ϕ), and energy storage coefficient (K_e) decrease with the increase of dissolution rate (η), with the maximum decreases being 14.11%, 12.86%, and 9.72%, respectively. At the same dissolution rate, the pore diameter (d) exerts a more significant influence on the variations of various parameters in holed limestone than the pore number (n). σ_p, σ_cd, σ_cd /σ_p, and K_e all increase with increasing confining pressure (σ₃). The failure mode of holed limestone is not affected by hole number, and exhibits a conical shear failure without penetrating through the specimen when the hole diameter is greater than 15mm. A fractal damage constitutive model was developed for holed limestone, and the consistency between theoretical predictions and experimental results substantiates the validity of the proposed model. The concluding remarks can provide a basis for further research on the holed limestone and karst landslides.

Gas pressure is one of the important factors that induce and aggravate coal and gas outburst(referred to as outburst). In order to further reveal the effect of gas pressure on outburst coal bodies in tectonic zones, uniaxial compression tests of outburst coal bodies under gas pressure (spanning from 0 to 2.4 MPa) gradient were carried out. In conjunction with PFC discrete element numerical simulation, a systematic analysis was performed to investigate the influence mechanism of gas pressure on mechanical properties, damage evolution, crack propagation and energy evolution of coal bodies. The results show that gas pressure significantly diminishes the strength of outburst coal bodies. Both the uniaxial compressive strength and elastic modulus exhibit a nonlinear decline with increasing gas pressure, with maximum reductions of 15.85% and 34.47%, respectively. Based on the damage variable defined by the cumulative count of acoustic emission events derived from simulations, the coal fracturing process can be categorized into four stages: pore fracture closure, micro-crack initiation, propagation, and coalescence. The acoustic emission signals transition from weak to strong, while the damage variable at the peak point decreases as gas pressure increases. Through a collaborative analysis of both experimental results and simulation results, it is found that the failure mode of outburst coal bodies is predominantly governed by gas pressure. This failure mode can be categorized into two types: tension-shear-slip conjugate failure (occurring at gas pressures of 0,0.4,1.6, and 2.0 MPa) and compression-shear-tension-slip conjugate failure (observed at gas pressures of 0.8,1.2, and 2.4 MPa). Notably, the crack density under compression-shear-tension-slip conjugate failure is markedly higher compared to that under tension-shear-slip conjugate failure. Gas pressure significantly affects energy storage and dissipation. Specifically, at low pressure (ranging from 0.4 to 2 MPa), adsorbed gas reduces effective stress and consequently weakens the energy storage efficiency. Conversely, at high pressures (spanning from 1.6 to 2.4 MPa), there is a substantial increase in both energy accumulation and release intensity, thereby sharply elevating the risk of outburst.

The assessment and exploitation of natural gas hydrate resources depend on the accurate identification of the distribution and thickness of the hydrate stability zone. This study develops a calculation method for determining the hydrate reservoir stability zone, grounded in the generalized phase equilibrium theory. Furthermore, the analysis software has been developed, taking into account the effects of seawater salinity, pore capillarity, and temperature offset on the hydrate stability zone. The experimental results from reservoir samples in the Qiongdongnan sea area reveal that the phase equilibrium characteristics of hydrates can be consistently characterized by a three-dimensional generalized phase equilibrium surface, encompassing temperature, pressure, and unhydrated water content. By comparing with mature software, the reliability of the proposed stability zone calculation method and software is confirmed. Stability zone calculation and analysis are subsequently performed based on the measured sample phase equilibrium curve and field conditions. The results show that, in addition to water depth, seabed temperature, geothermal gradient, and seawater salinity, the effective pore radius of sediments and temperature offset exert a significant influence on the lower boundary of the stability zone. Failure to account for the effects of pore effective radius and temperature offset results in an overestimation of the lower boundary of the stability zone by 77.4 m within this gas hydrate target area, significantly affecting the accurate assessment of resource quantity. These findings can provide theoretical support and a data reference for predicting the stability zone and accurately assessing the resource quantity of marine natural gas hydrates.

Shield slurry is a mixture of mud and slag generated from tunnel excavation. It is difficult to be directly utilized due to its high fines content, high fluidity, and low strength. The study introduces a novel approach involving initial granulating followed by compaction of the slurry utilizing phosphogypsum-based cementitious materials to address difficulties associated with the continuous solidification construction of slurry with high-water-content. The research investigates the particle size distribution of the granulated slurry and its strength characteristics post-compaction. Findings reveal that granulation significantly increases particle size of the slurry significantly increased, with substantial portion of fine particles (<0.075 mm) being transformed into “sand-sized particles” (0.075-2 mm). This transformation enhances inter-particle friction, thereby improving both the shear and compressive strengths of the granulated slurry. The phosphogypsum-based cementitious materials content, granulation duration, and curing age collectively influence the physical and mechanical properties of the granulated slurry in a synergistic manner. The optimal conditions for achieving a harmonious balance between granulation and compaction-solidification are as the phosphogypsum-based cementitious material content of 20% 20%, a granulation duration of 14 days, and a curing age of 28 days, resulting in a compressive strength of 5.62 MPa. Meanwhile, some samples after the compressive strength test were taken to conduct mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) tests, revealing the strength formation mechanism of slurry granulated into sand and solidified into blocks. Finally, the cost per unit strength and carbon sequestration rate associated with the utilization of phosphogypsum-based cementitious materials for granulating and solidifying slurry were calculated, and their economic and environmental advantages were assessed. The results show that the continuous implementation method of “granulation-compaction-solidification” is reliable and cost-controllable, offering technical support for the resource utilization of shield slurry.

Earthquake is one of the important driving factors that induce slope instability. Accurate evaluation of the stability of three-dimensional (3D) loess slopes under earthquake needs further study. To address the stability of loess slopes under nonlinear conditions, this study develops a theoretical calculation method for the seismic stability of 3D loess slopes that incorporates the effect of tension cut-off (T-C). Based on the upper bound theorem of limit analysis, a multi-tangent technique is employed to approximate the nonlinear strength criterion in a piecewise manner. The modified strength envelope of tensile strength accounting for the cut-off effect is derived in Mohr space, upon which a novel 3D multi-cone failure mechanism is constructed. In addition, this method employs the pseudo-dynamic approach to characterize seismic loading, which can accurately and comprehensively evaluate the influence of T-C and seismic effects on slope stability. The results indicate that T-C significantly affects slope stability and the contours of sliding surfaces, with particularly notable effects in slopes characterized by high width-to-height ratios or steep gradients. As the degree of T-C increases, both slope stability coefficients and safety factors decrease markedly, and tensile failure characteristics at the slope crest become increasingly prominent.

To address the limitations of the current reinforcement technology for multi-stage high-fill slopes, this study proposes a novel flexible supporting structure called frame-prestressed T-shaped fixed anchors (FPTA) that achieves superior reinforcement performance. Firstly, based on the asymmetric distribution of the pullout failure mode of the T-shaped anchor along the burial depth, the concept of the asymmetric failure influence height lz is introduced. A unified mechanical model for the horizontal ultimate pullout resistance of the T-shaped anchor is established, and the anchoring action is represented as the additional cohesion Δc based on the pseudo-cohesion theory. Secondly, a seismic stability analysis method for multi-stage fill slope reinforced by FPTA is developed by using the pseudo-dynamic approach combined with the upper-bound limit analysis method. This method considers the inhomogeneous and damping properties of the fill soil, the interaction between the T-shaped anchor and the soil, and the geometric characteristics of the multi-stage slope. Then, the comparative analysis between the proposed method, experimental results, and existing research serves to demonstrate the validity and reliability of this method. Finally, the effects of soil strength parameters, slope geometry parameters, supporting parameters, and seismic parameters on slope stability are elucidated. This study provides technical guidance for multi-stage fill slope reinforcement engineering projects and offers a theoretical basis for the seismic design of multi-stage fill slopes reinforced by FPTA.

Near-fault pulse-like ground motions are characterized by long periods, large amplitudes, and high energy release, exhibiting significantly higher destructive power than conventional ground motions. However, the dynamic response characteristics and failure mechanisms of slopes subjected to pulse-like ground motions remain unclear. Based on the universal distinct element code (UDEC), a generalized model of opposing rock slopes in a valley was established, and the dynamic response characteristics of rock slopes under pulse-like ground motions were systematically analyzed. Additionally, the relationship between the directional asymmetry in pulse-like ground motion intensity and the aspect effects of earthquake-induced landslides was investigated. The results indicate that, under typical pulse-like ground motions, the dynamic response of the opposing rock slopes in the valley is strongest during the velocity pulse phase. The maximum acceleration amplification factor on the right slope reaches 1.57 times that of the left slope, with the cumulative displacement being as much as twice that of the left slope. Pulse-like ground motions generally exhibit pronounced directional asymmetry in intensity, which is a key dynamic mechanism leading to significant aspect effects of earthquake-induced landslides. The amplitude-based index, peak ground velocity (PGV), demonstrates the highest correlation coefficient (r=0.82) with cumulative slope displacement, significantly surpassing other indexes such as peak ground acceleration (PGA), Arias intensity (Ia), specific energy density (SED), velocity-to-acceleration ratio (V/A). It is the most accurate ground motion intensity index for characterizing the directional intensity differences of pulse-like ground motions and their impacts on the stability of slopes with different orientations. The research outcomes offer scientific underpinning for analyzing slope stability and assessing seismic landslide hazards under the influence of pulse-like ground motions.

To address the challenges in quantitatively evaluating rock fracture evolution and fracture development intensity within the strongly compressed strata of the Kuqa Depression in the Tarim Basin, this study introduces a method for assessing fracture development intensity. This method is grounded in stress state analysis and is realized through a series of rigorous steps, including geological data analysis, rock mechanical testing, formulation of failure criteria, and development of computational software. The research reveals that deep-seated rocks in the Kuqa Depression exhibit high uniaxial compressive strength, low Poisson’s ratio, and brittle-dominated mechanical properties under intense compression. The failure criterion must account for the intermediate principal stress effect and confining pressure dependency. Building on octahedral energy theory, a generalized failure criterion is established, integrating tensile microcrack initiation and frictional slip coupling mechanisms. A four-level index system for fracture development intensity, centered on the relative fracture surface tensor distance, is proposed, along with supporting computational software. Validation using logging and core data from the Jurassic Ahe Formation in Wells DB5 and DT2 in the Kuqa Depression demonstrates a predictive accuracy exceeding 80% for fracture development intensity, which aligns well with imaging logging results. This method surmounts the constraints of conventional logging techniques confined to localized wellbore detection, enabling dynamic fracture evaluation across entire well sections and throughout their lifecycle. It provides a quantitative basis for optimizing stimulation strategies in ultra-deep hydrocarbon reservoirs under intense compression and for controlling wellbore stability.

The scale effect is considered one of the primary reasons for the inaccuracy in predicting the deformation of rockfill dams. However, the scaling behaviors of blasted rockfill and gravel materials differ significantly. Preliminary analyses suggest that this is due to particle-shape differences manifesting in packing densification and crushability, yet a comprehensive mechanistic explanation remains lacking. To address this, discrete element method (DEM) simulations were conducted on both prototype and scaled specimens of rockfill and gravel, considering the size-dependent crushing strength of particles and the effect of coordination number on particle strength. Rockfill numerical specimens were generated based on 3D-scanned blasted rock fragments, while gravel was simplified as an assembly of spherical particles. The results reveal that the particle shape’s influence on the contact force chain network is the main factor responsible for the differences in scale effects between rockfill and gravel. The strong interlocking effect among irregular particles weakens the densification effect induced by broader gradation, resulting in decreased mechanical coordination number and lower anisotropy coefficients of both normal and tangential contact forces. This ultimately leads to reductions in deformation modulus and shear strength. In contrast, spherical particle assemblies exhibit the opposite trend: enhanced packing densification, a more stable force chain network, and increased stiffness and strength with scaling. Moreover, the decrease in particle strength mitigates modulus variations induced by scaling in the spherical system, whereas this influence is less significant in the irregular particle system.

During tunnel excavation in phyllite formations, the stress concentration effect in surrounding rock and the mechanical effect of beddings significantly influence the deformation and failure of rock masses, commonly resulting in asymmetric deformation. To investigate the impact of phyllite bedding dip angle on the deformation and failure of surrounding rocks, this study examined the deformation characteristics, stress evolution, and progressive failure mechanisms of cavity-containing phyllite specimens with five bedding dip angles (0°, 30°, 45°, 60°, and 90°) under compression. Experimental results indicate that the failure load of cavity-containing phyllite exhibits a U-shaped trend with increasing bedding dip angle. By adopting the digital image correlation (DIC) technology, the influence of bedding dip angle on the failure mode of cavity-containing specimens was analyzed. At a dip angle of 0° , high strain concentration zones developed at the roof and floor of the cavity, resulting in tensile failure. When the dip angle ranged from 30° to 60°, strain concentration bands propagated along the beddings due to the combined effect of cavity stress concentration and bedding plane mechanics, thereby inducing shear-slip failure. At a dip angle of 90°, strain concentration bands extended vertically, leading to tensile-splitting failure along the beddings. The mesoscopic failure mechanisms of cavity-containing phyllite specimens were studied using the combined finite-discrete element method (FDEM) incorporating the cohesive zone model (CZM). Based on the experimental results, the feasibility and applicability of this modeling method for simulating the mechanical behavior of cavity-containing layered rock specimens were validated. Numerical simulation analyses of biaxial loading tests reveal that confining pressure not only enhances the bearing capacity of the specimens and reduces the anisotropy ratio, but also induces transitions in the failure modes of specimens with varying dip angles.

Accurate prediction of tunnel seepage behavior, which is critical for estimating water inflow and ensuring construction and operational safety, is often hindered by the inherent difficulty in characterizing the formation's permeability properties. To address steady-state and transient seepage around shallow underwater tunnels, a physics-informed neural networks (PINNs) model for forward and inverse analyses was established in this study. By leveraging the automatic differentiation of neural networks to encode the governing equations, the PINNs model's loss function integrates physical constraints (governing equations, boundary conditions and initial conditions) with data mismatch from monitoring points. The effectiveness and reliability of PINNs model were validated through comparisons with benchmark solutions derived from the finite difference method (FDM). Subsequently, forward and inverse analyses were performed for steady-state and transient seepage in tunnel, considering two typical boundary conditions: constant total head and zero water pressure. The results show that in terms of forward solving, by introducing spatiotemporal coordinate affine transformation, the PINNs model can effectively simulate the transient and steady state process of tunnel seepage in anisotropic strata and achieve accurate deduction of its seepage behavior. Inversion analyses of the PINNs model can not only swiftly and accurately acquire key parameters such as the permeability coefficient, but also simultaneously deduce the seepage morphology associated with tunnel seepage. The proposed data-physics fusion PINNs model effectively reconstructs the seepage field and predicts the total head evolution around tunnel, and provides an effective way for accurate and rapid estimation of tunnel water inflow.

To address the challenges of inadequate feature fusion, loss of fine-grained details, background noise interference, and suboptimal computational efficiency in existing rock fracture identification methods, the present study proposes a fracture recognition approach based on the triple feature efficient-fusion U²-Net(TFE-U²-Net) model. This approach is integrated with an image preprocessing algorithm based on gray-based fracture region preselection(GFRP) to significantly enhance the processing efficiency for large-scale, high-resolution images. The proposed improvements include: (1) integrating a triple feature fusion (TFF) mechanism into the U²-Net framework to strengthen multi-scale feature extraction; (2) embedding an efficient channel attention (ECA) module to suppress background noise and enhance feature representation; and (3) replacing standard convolutions with depthwise separable convolutions to significantly reduce model complexity. Based on a self-constructed rock fracture image dataset, ablation studies and comparative experiments were conducted to validate the model’s performance. Experimental results show that the proposed method reduces the model parameter count by 39.2% compared to the original U²-Net, while achieving IoU and F₁ scores of 81.07% and 89.55%, respectively—significantly outperforming baseline models. The TFF mechanism effectively mitigates detail loss, and the ECA module enhances the model's robustness under noisy conditions.

Accurate acquisition of the orientation and spatial distribution of rock mass discontinuities is essential for the stability analysis of high and steep rock slopes. Conventional clustering-based methods, which rely heavily on point cloud normal vectors, often suffer from significant identification errors when abrupt variations exist in the point cloud data. To address this limitation, a discontinuity mapping approach integrating geometric and signal features of point cloud is developed, improving both the accuracy and robustness of the identification result. Furthermore, the k-means++ algorithm is enhanced by refining its decision-making process and optimizing cluster center selection, enabling more effective segmentation and information extraction of rock mass discontinuities. The proposed method is applied to a rock slope in Zhejiang, China. The results demonstrate that it can effectively identify discontinuities from point cloud data, accurately extract their orientations, and perform dominant set classification. Comparative analysis with the DBSCAN algorithm further verifies the effectiveness of the proposed approach. Validation against manual measurements shows that the errors in dip direction and dip angle are within 3° and 4°, respectively, indicating that the method provides accurate and reliable results with strong engineering applicability.

The application codes of the National Natural Science Foundation of China (NSFC) serve as the institutional cornerstone for science funding. Their scientific rigor and forward-looking nature directly influence the direction and efficacy of disciplinary development. In 2025, the discipline of Architecture and Civil Engineering underwent a systematic review and optimization of its research directions and keyword systems. Specifically, the "E0807 Geotechnical and Foundation Engineering" section expanded from its original 5 research directions to 20, with the keyword system correspondingly improved systematically, representing a profound adjustment of the discipline's connotation and extension. This paper systematically elucidates the overall context and rationale behind this optimization of research directions and keyword system. Furthermore, it provides an interpretation of future development trends and strategic directions for the discipline.