To elucidate the unclear mechanism by which the geo-stress field influences the cracking of layered soft rock tunnel linings,this study examines a typical layered soft rock tunnel along the Wen-Ma expressway as a case study.By integrating model tests with numerical simulations,we investigate the deformation,stress,and failure behavior of layered soft rock tunnel linings under the impact of the geo-stress field.The damage characteristics and cracking patterns of the tunnel lining structure under varying lateral pressure coefficients are analyzed,thereby revealing the mechanism through which the geo-stress field affects tunnel lining cracking.The results indicate that,with a bedding angle of 45° and a strike of 90°,as the lateral pressure coefficient increases from 0.5 to 1.5,the morphology of the lining cracks transitions from vertical compression failure to bedding-plane dominated failure,and subsequently to horizontal compression failure.The cracking pattern evolves from tensile-shear composite failure to shear failure,and then back to tensile-shear composite failure.Correspondingly,the location of cracking shifts from the vault to the right spandrel,and from the left arch foot to the left haunch.When the lateral pressure coefficient is 1.00,the stress distribution of the surrounding rock is the most uniform,leading to minimal deformation and contact pressure of the lining,maximal bearing capacity of the lining,and optimal overall stability of the tunnel.Further analysis reveals that the location of surrounding rock damage exhibits spatial consistency with the area of lining fractures.The surrounding rock damage manifests as compression failure along the normal bedding plane surrounding the tunnel,along with shear sliding along the bedding plane away from the tunnel area.
The closure behavior of rock joints significantly influences their shear mechanics.This study employs pressure-sensitive films to measure three groups of sandstone joints,discussing the relationship between effective contact characteristics and shear strength.The results indicate that:(1)Under identical normal stress,the effective contact area ratio varies with different shear directions.As normal stress increases,the effective contact area ratio exhibits a linear growth trend,ultimately reaching approximately 50％of the actual contact area ratio.(2)Variations in effective average contact stress also show significant differences across shear directions.Additionally,the rougher the joint surface,the more pronounced the fluctuations in effective average contact stress.Furthermore,the average effective dip angle decreases following a negative exponential trend as normal stress increases,gradually approaching a stable value indicative of a fully contacted state.(3)An effective roughness indicator,which accounts for the influence of normal stress,is modified based on the effective contact area ratio.Building on this,a new peak shear strength model for rock joints is developed using the Barton criterion.This model satisfies boundary condition constraints,and its accuracy in predicting the peak shear strength of rock joints has been validated through direct shear tests and comparisons with several published datasets.These findings provide a theoretical foundation for understanding the shear mechanisms of sandstone joints.
Elastic beam-spring models are widely used in performance-based design for confined excavations;however,existing methodologies are often insufficient in accurately capturing the evolution of earth pressures under confined spatial constraints and the nonlinear stiffness behavior of soil.To address these limitations,this study develops a hardening soil-spring model with small-strain stiffness within a nonlinear elastic beam-spring framework to predict deformations in confined excavations.The proposed model features a displacement-dependent earth pressure formulation with a modified factor applied to the active side of the retaining structure,effectively accounting for soil arching effects and horizontal shear stresses within the confined soil.On the passive side,nonlinear soil springs simulate both the hardening behavior and small-strain characteristics of soil based on the hardening soil model with small-strain stiffness(HSS).The proposed model is validated against centrifuge test results and numerical simulations,followed by a parametric analysis that examines the effects of excavation depth,confined soil width,wall bending stiffness,and soil stiffness parameters—including Young's modulus and small-strain stiffness—on wall deflections.Additionally,the model is applied to a real-world case involving deep excavations adjacent to bridge piers in a coastal composite stratum,with soil parameters derived from in-situ standard penetration tests(SPT)and cross-hole seismic tests.The close agreement between predictions and field monitoring results highlights the practical applicability of the proposed model.
To enhance the long-term service performance of solidified soft soil in plateau regions,this study employed ordinary Portland cement for stabilization.A series of unconfined compression tests,direct shear tests,and microstructural characterization techniques(XRD,SEM,NMR)were utilized to systematically investigate the strength deterioration patterns of cement-stabilized soil under freeze-thaw cycles and elucidate the intrinsic relationship between macroscopic mechanical behavior and microscopic mechanisms.The results show that the strength deterioration of cement-stabilized soil exhibits distinct stage characteristics.The first five freeze-thaw cycles result in the most significant strength reduction,with markedly diminished effects observed thereafter,identifying this initial phase as the critical period for strength degradation.A predictive model based on a 30-year service life established strength deterioration thresholds.The stress-strain curves reveal a three-stage evolution,with specimens demonstrating similar strength development trends in the linear elastic stage across all cement contents,followed by a sharp stress drop post-peak,indicating a notable transition from plastic to brittle failure.The incorporation of cement significantly enhances soil strength,with the unconfined compressive and shear strengths of specimens containing 4％-10％cement after 10 freeze-thaw cycles substantially exceeding those of untreated soil.The increase in cohesion was significantly more pronounced than that of the internal friction angle.Microstructural analysis indicates that repeated freeze-thaw cycles weaken interparticle bonding,reduce particle contacts,and promote pore evolution and development,thereby providing a microscopic interpretation of the macroscopic strength deterioration mechanisms.These findings offer theoretical and technical support for the application of soil stabilization technologies in cold plateau regions.
Time-dependent deformation of rock and soil masses plays a fundamental role in their long-term evolution and instability.However,conventional theories are often insufficient to characterize the differential features of deformation evolution in both temporal and spatial dimensions.To address this limitation,the concept of differential time-dependent deformation is proposed,which states that different parts of a geotechnical system undergo creep deformation at different displacement rates.Based on this concept,a systematic theoretical framework is established,ranging from the analysis of time-dependent response mechanisms to the formulation of constitutive models.First,homogeneous landslide basal-friction experiments and slope model tests containing weak interlayers were conducted.Combined with particle image velocimetry(PIV),digital image correlation(DIC),and environmental scanning electron microscopy(ESEM),the spatial distribution characteristics of deformation in geomaterials were systematically revealed.The results indicate that deformation progressively intensifies from the rear edge to the toe of the slope and from shallow layers to deeper regions,accompanied by distinct time-dependent response mechanisms in different zones.Based on these observations,a visco-elastic-plastic constitutive model is developed by connecting a Burgers model in series with a plastic element incorporating strain-softening behavior.The model quantitatively describes the gradual degradation of cohesion and internal friction angle during the differential time-dependent deformation process of geomaterials.The proposed model is implemented into the FLAC and 3DEC numerical platforms.Numerical analyses demonstrate that the model successfully reproduces the complete deformation process of the Danba landslide,including initial deformation,steady-state creep,and accelerated failure.In addition,it effectively captures the interface effect occurring at the boundary between soft and hard rocks in the Jinping Hydropower Station slope and reveals the formation mechanism of deep unloading fractures.The proposed theoretical framework clarifies the universality and controlling role of spatiotemporal differential deformation during the time-dependent evolution of geomaterials,providing a new theoretical basis for deformation-failure warning and dynamic stability assessment in geotechnical engineering.
The Xihoumen Rail-road Bridge is the first in China to implement a novel rock anchorage system.A 1:10 in-situ scaled model test was designed and conducted to systematically investigate the deformation characteristics,mechanical response,and failure mechanism of the structure.The results indicate that,under anchor cable tension,the deformation of the surrounding rock near the rear anchor plate is significantly greater than that near the front anchor plate,with the maximum ground surface deformation occurring at the centerline between the two anchor plates at the front anchorage face.Vertically,the deformation decreases approximately linearly from the bottom edge of the rock anchorage zone toward the ground surface.Strain analysis reveals that the surrounding rock is predominantly under compression,with the most pronounced compression occurring near the rear anchor plate;additionally,vertical compression and local tensile effects at the bottom edge of the rock anchorage zone are also evident.Based on the load-displacement relationship,strength analysis shows that the proportional limit strength,yield strength,peak strength,and residual strength of the model anchorage structure are approximately 4P,7P,11P,and 10P,respectively,where P represents the design load.The failure process unfolds sequentially through rear-edge tensile cracking,lateral shearing,and basal shearing.These findings elucidate the load-bearing mechanism and failure evolution of the novel rock anchorage system,providing valuable insights for the design and construction of similar anchorage systems in large-span suspension bridges.
This study investigates the dynamic response behavior and failure mechanisms of low-angle reverse-inclined sand-mud interbedded rock slopes.A refined three-dimensional geological model was developed using the FLAC3D platform to accurately replicate the cliff-slope topography,with precise control over the spatial distribution of sandstone-mudstone interlayers.The Arias Intensity(AI)and Hilbert-Huang Transform(HHT)techniques were employed to perform time-domain dynamic response analysis and time-frequency domain energy analysis(including peak Hilbert energy spectral amplitude,PHESA),respectively.This approach enabled a systematic investigation of energy evolution patterns and spatial damage distribution within the slope structure.The key conclusions are as follows:(1)Acceleration and AI responses indicate that the slope's dynamic response exhibits an amplification effect with elevation,which is,however,mitigated by the presence of hard sandstone layers;(2)The Hilbert energy spectrum reveals that energy is concentrated in the low-frequency band of 0-5 Hz;(3)AI and PHESA identify two high-response zones:the cliff on the left boundary and the main slope on the right boundary;(4)Based on energy evolution analysis(using δPHESA<0 as the criterion for rock mass failure),two typical failure modes were identified:"tensile cracking-sliding-shear combination"and"tensile cracking-bending-shear combination."The findings of this study provide a theoretical foundation for the seismic design and disaster prevention of similar rock slopes.
To investigate the characteristics of near-fault ground motion and the influence of novel mitigation measures on tunnel lining damage mechanisms,a refined three-dimensional numerical model of the tunnel-surrounding rock system was developed based on the Kangding No.2 Tunnel.Employing a probabilistic framework with incremental dynamic analysis(IDA),we systematically compared the dynamic responses and damage probabilities of conventional linings and rubber-sand concrete(RSC)constrained damping linings under far-field,near-fault non-pulse-like,and near-fault pulse-like motions.Peak ground velocity(PGV)and moment capacity ratio(MCR)emerged as the optimal intensity measure(IM)and damage measure(DM),respectively.Fragility analysis revealed that the RSC constrained damping layer significantly mitigates damage,reducing the probability of extensive damage by 26.7％at the Design Basis Earthquake level.Consequently,the risk profile transitioned from being dominated by extensive damage to a state where intact and extensive damage became nearly equiprobable.Ground motion characteristics were a dominant factor,with structural fragility following the order:near-fault pulse-like>near-fault non-pulse-like>far-field;the velocity pulse was identified as the critical driver of damage,more so than epicentral distance.Furthermore,concerning brittle failure induced by pulse-like motions,the traditional regression-based fitting method exhibited systematic biases in limit state assessment,characterized by overestimating risk in low-intensity regions and underestimating it in high-intensity regions.In contrast,the assessment results based on the critical point set method demonstrated greater rationality and physical clarity.These findings provide a valuable reference for the seismic design and performance enhancement of tunnels in near-fault regions.
Microseismicity,as an"acoustic manifestation"of nonlinear mechanical behavior in rock mechanics and engineering,plays a crucial role in the accurate picking of first-arrival times for the prediction and early warning of deep coal-rock dynamic disasters in China.Due to the combined effects of complex operational environments and unique geological conditions,microseismic signals in deep mining areas typically exhibit high-dimensional,nonlinear,and low signal-to-noise ratio characteristics.To address the limitations of conventional picking methods,such as low accuracy,strong manual dependence,and poor efficiency,this study proposes an intelligent microseismic signal recognition method based on energy dissipation and multiscale complexity evolution.First,variational mode decomposition is employed to perform multiscale energy decomposition of microseismic signals,and the dynamic evolution characteristics of different frequency bands are characterized from the perspective of energy dissipation and aggregation.Permutation entropy is then introduced to quantitatively evaluate the complexity of each mode,thereby enabling the adaptive suppression of modes dominated by energy dissipation.Subsequently,one-dimensional non-local means filtering is applied for energy-differentiated reconstruction to enhance the structural characteristics of the principal seismic phase.Sliding kurtosis and fractal dimension features are further extracted to construct a fractal feature-based combined kurtosis seismic phase timing identification algorithm(Fractal-PAI-K)fusion scoring function,in which abrupt complexity changes are used to characterize the transition of energy from a dissipative state to an aggregated state.Finally,high-precision automatic identification of the P-wave first arrival is achieved through dynamic thresholding.A case study based on measured microseismic data from a deep mine demonstrates that the proposed method can stably identify first-arrival times under various signal-to-noise-ratio conditions,with a mean absolute error of less than one sampling interval and a picking success rate exceeding 95％.Compared with conventional methods such as complete ensemble empirical mode decomposition with adaptive noise and wavelet thresholding,the proposed method reduces the root mean square error by up to 54.3％and improves the output signal-to-noise ratio metric by up to 82.5％.These results indicate that the collaborative analysis framework integrating energy dissipation and complexity exhibits excellent robustness under low signal-to-noise-ratio conditions,spectral overlap,and non-stationary noise,and can provide reliable technical support for microseismic signal recognition and source localization in the real-time monitoring of dynamic disasters in deep mines.
Laminated shale is a common roof type in coal mine roadways,where its significant anisotropic brittle characteristics often induce asymmetric large deformation and roof fall accidents.However,existing numerical simulation studies frequently overlook the influence of bedding plane orientation and lack calibration against in-situ measurements,making it difficult to accurately reveal the mechanical properties and deformation patterns of shale roofs.Based on in-situ measurements from five typical U.S.coal seams(e.g.,Lower Kittanning and Pittsburgh),this paper proposes a systematic model calibration workflow combining theoretical analysis and numerical simulation.The procedure includes:calibration of vertical and horizontal stresses,calibration of roof sag and cable bolt loads,and verification of anisotropic brittle failure characteristics.Subsequently,a FLAC3D roadway numerical model incorporating an anisotropic brittle failure criterion was established,realizing the coupled characterization of anisotropy in shale strength and elastic modulus,cohesion-weakening friction-strengthening behavior,and dilatancy features.Furthermore,roadway models covering four typical mining geological conditions were constructed:highly laminated shale roofs,high horizontal stress,deep three-pillar systems,and single-pillar systems.The simulated ranges of vertical stress(5-48 MPa)and horizontal stress(6-42 MPa)effectively cover the geo-stress conditions of most U.S.coal seams.Compared with traditional methods,the calibrated model more accurately characterizes strata behaviors,such as stress distribution,roof sag,cable loads,and failure patterns.It reveals the asymmetric failure mechanism of laminated roofs and clarifies the risk of roof cutting and large deformation in single-pillar systems.This study deepens the understanding of the anisotropic brittle failure mechanism of laminated shale at the entry scale and provides a reliable numerical analysis framework for the stability analysis of longwall tailgates/headgates under complex geological conditions.
Negative Poisson's ratio(NPR)bolt steel is a novel high-strength,high-toughness anchor bolt material that has been independently developed.To investigate its dynamic cyclic shear resistance,shear tests were conducted on NPR bolt-anchored joints under cyclic dynamic loading.The effects of anchoring conditions,joint surface roughness,shear displacement amplitude(ua),and normal load on the dynamic cyclic shear performance were systematically analyzed.The results demonstrate that NPR anchor bolting significantly enhances the dynamic cyclic shear capacity of jointed rock masses.A smaller shear displacement amplitude(ua)leads to less mobilization of the bolt's shear resistance and reduces frictional interlocking between joint surfaces,resulting in lower peak shear strength during the cyclic phase.As the cyclic shear displacement amplitude increases,the degradation effect of the bolt becomes more pronounced,heightening the likelihood of shear fracture.Under constant normal stiffness boundary conditions,the shear force-shear displacement curves exhibit significant plastic hardening characteristics across all phases,with an exception of a decline in the forward peak shear force(Ffp)at cycle numbers N=1 to 2.In contrast,under constant normal load boundary conditions,the mechanical behavior exhibits plastic softening.A comparative study between traditional Q235 steel and NPR steel reveals that,under Q235 steel anchoring conditions,the peak shear resistance during the conventional shear phase increased by 62.21％,with fracture occurring at a shear displacement of 7.076 mm.In contrast,NPR anchor steel maintained high shear resistance throughout the test without fracturing,achieving a 140.90％increase in peak shear resistance,thereby demonstrating excellent resistance to dynamic cyclic shear loading.
Deep-seated slopes,characterized by complex geological structures and deeply incised topography,are widely distributed in the metamorphic rock terrains of the Shikoku region in western Japan.This study aims to elucidate the correlation between seismic ground motion amplification and co-seismic instability mechanisms in such slopes,focusing specifically on the Azue metamorphic rock slope located in Tokushima Prefecture.Utilizing dense microtremor observations,geophysical surveys,geological investigations,and geo-mechanical testing,we systematically analyzed the seismic response characteristics of potentially unstable slope blocks using the horizontal-to-vertical spectral ratio(HVSR)method and Time-Frequency Polarization Analysis(TFPA).The key findings are as follows:(1)The slope exhibits a multi-scale resonance structure:low-frequency resonance(3-5.5 Hz)is governed by deep-seated wave impedance interfaces,with variations in resonance amplitude(HVSR)among blocks indicating systematic differentiation in the deep structure;high-frequency resonance(8-12 Hz)correlates with shallower interfaces and demonstrates relatively uniform transitions;mid-frequency resonance(6.5-7.5 Hz)is triggered by a low-dissipation"resonant cavity"formed by a surface fracture system,resulting in discrete anomalous distributions.(2)The predominant direction of deep-seated resonance aligns with the strike of high-stiffness joints,while shallow resonance is parallel to the slope's free face direction,reflecting the influence of stress state on wave impedance anisotropy.The fracture system induces localized resonance perpendicular to its strike.(3)Pre-existing weak layers within the slope mass transform into resonance layers exhibiting distinct wave impedance contrasts during seismic shaking,which dominate ground motion amplification and strength degradation.The synergistic amplification of seismic forces by deep,shallow,and surface"cavity"resonances predisposes the slope to large-scale bedrock sliding and shallow local instability,respectively.This investigation of the multi-scale ground motion amplification response provides a novel framework for understanding the failure mechanisms of complex deep-seated slopes during earthquakes.
In order to accurately calculate the jacking force required for ultra-shallow buried rectangular pipe jacking under the dual influence of complex geology and supporting structure,the jacking force composition mechanism and influencing factors of rectangular pipe jacking in complex ultra-shallow buried strata were studied.Based on the large-scale pipe-rock friction mechanical property test experimental device,the contact friction characteristics of pipe joints sliding on different rock contact surfaces were analyzed.The main results are as follows:(1)Considering the influence mechanism of different strata and supporting structures on the friction resistance of rectangular pipe jacking,a calculation model of rectangular pipe jacking force suitable for rock strata and composite strata is proposed for the first time.(2)The rock strength,particle size and pressure of the contact surface have no significant effect on the friction coefficient of the pipe section sliding on the rough contact surface of the rock,while the friction coefficient of the contact interface will be significantly reduced after adding the anti-friction slurry.(3)The dry and wet friction coefficients of the pipe section in the medium weathered and slightly weathered granite strata can be taken as 0.719 and 0.629 respectively,and the dry and wet friction coefficients in the strongly weathered granite strata can be taken as 0.675 and 0.603 respectively.(4)Engineering examples show that the error between theoretical and measured jacking force data is less than 7％in soft soil,soft rock and normal excavated rock strata,which confirms the accuracy of the jacking force calculation model and calculation parameters in this paper.The research results of this paper can provide an important basis for the calculation of jacking force in pipe jacking engineering in similar strata.
To elucidate the long-term shear strength of anchored jointed rock masses(AJRMs)under shear creep-impact conditions,shear creep-impact tests were performed under constant normal stiffness boundary conditions.The failure mechanisms associated with shear and normal creep disturbances in AJRMs were examined across various combinations of joint roughness coefficient(JRC)and impact energy(Q).Moreover,a method for determining long-term strength based on Weibull distribution evaluation was proposed,and a theoretical calculation formula for the long-term strength of AJRMs under impact disturbance was established.The results indicate that normal creep deformation undergoes a sequential process involving asperity climb-induced dilation,asperity damage,and asperity shearing-off,which subsequently accelerates shear creep deformation.The instantaneous shear strain induced by impact loading exhibits a"jump-recovery-accumulation"evolution pattern.Under impact disturbance,the shear steady-state creep-rate curves reveal two distinct evolutionary forms:the"gradual-increase"type and the"stable-sudden-rise"type.Utilizing the Weibull distribution evaluation method with a 50％failure probability,the quantified long-term strength values fall within the reasonable range established by the traditional isochronous stress-strain curve method,with a relative expected error of 5％to 10％.A comparison with the indirect long-term strength determination method validated the parameter selection and rationality of the theoretical calculation model.These findings provide theoretical guidance for long-term instability control and support structure design in deep anchored jointed rock masses.
This paper employs a poroelastic half-space model to analyze the dynamic response of saturated soil induced by a vertically vibrating pile.A two-step analytical framework is utilized:the pile response is first derived using a plane strain model,which is subsequently input into the half-space model to obtain the soil's dynamic response through Fourier-Hankel transforms.Results under various conditions align well with existing solutions,thereby validating the proposed model.Based on Biot's theory of poroelasticity,this study elucidates that fluid-solid coupling significantly increases the compression wave velocity,while the radial propagation of pore pressure is less influenced by variations in soil shear stiffness.These findings provide theoretical support for vibration isolation design and pile integrity testing using the parallel seismic method in saturated soils.
Excavation in underground engineering triggers complex true triaxial stress redistribution,resulting in intricate ductile-brittle behavior in rocks.However,there is a notable absence of mechanical models that accurately characterize this behavior under true triaxial stress.Therefore,within the framework of irreversible thermodynamics,this study derives a function to describe the nonlinear behavior of rocks and,in conjunction with classical elastoplastic mechanics theory,establishes a three-dimensional elastoplastic damage constitutive model capable of simultaneously capturing plastic hardening and damage softening in rocks.Utilizing the finite element method and the cutting plane projection algorithm,a corresponding user material subroutine(UMAT)was developed using FORTRAN on the ABAQUS platform,facilitating the numerical implementation of the model.Through parameter sensitivity analysis,this research proposes a method for controlling the ductile-brittle transition behavior of rocks by adjusting key parameters(β and ζ).The validity of the proposed model was verified through true triaxial compression tests on sandstone.Comparative results between numerical simulations and experimental data indicate that the model effectively captures the mechanical properties and ductile-brittle transition behavior of rocks under true triaxial stress.Furthermore,the model can be simplified to an ideal elastoplastic model,an elastoplastic hardening model,or an elastoplastic hardening-softening model,demonstrating greater comprehensiveness and general applicability.This work provides a robust theoretical foundation for hazard analysis in underground engineering.
Landslides occurring along reservoir banks in narrow water bodies,due to local gradual water depth variations,may generate wave characteristics distinct from those in wider water bodies In this study,large-scale physical model experiments were conducted to investigate landslide-induced waves along reservoir banks in narrow water bodies.The wave propagation characteristics were analyzed in three specific regions:the water body above the riverbed(WRB),the water body above the opposite bank slope(WOB),and the water body above the original bank slope(WIB).The results reveal that the leading wave train,prior to the onset of run-up behavior,was influenced solely by the shoaling effect,without being affected by reflection,refraction,or breaking.The maximum relative amplitude of the first wave crest in the WRB and WOB regions occurred at an angle of 0° and decreased with increasing angles,while in the WIB region,it increased with increasing angles.The most significant attenuation of the first wave crest was observed at an angle of 10°,rather than at 0°.In regions closer to the landslide impact point,the propagating waves(excluding the edge waves in the WIB region)exhibited greater fluctuations.A relative distance of 4.85(equivalent to 1.7 meters)was identified as the boundary beyond which the kinetic energy from the landslide no longer significantly influenced the first wave.Additionally,in areas closer to the landslide entry point,the correlation between the relative period and angle became more pronounced.The average initial wave velocities in the WRB,WIB,and WOB regions were 0.93,0.87,and 1.03,respectively(all close to 1),indicating that the velocities of the first wave in all regions can be accurately approximated by long-wave theory.
Three-dimensional geological modeling serves as a fundamental basis for tunnel design and construction decision-making.However,the complexity and limited observability of geological bodies inevitably expose geological models to various uncertainties.Additionally,tunneling exhibits distinct stages and a sequential nature,wherein geological understanding deepens progressively as excavation advances,necessitating more advanced approaches to characterize and update these uncertainties.Consequently,a methodological framework for the integrated analysis and dynamic assessment of multi-source geological uncertainties in tunnel engineering has been developed.To systematically represent uncertainty in the modeling process,it is categorized into data uncertainty and methodological uncertainty based on its source.The former employs the quasi-Monte Carlo(QMC)method to perform random sampling of input data,generating multiple sample sets that capture the fluctuation features and uncertainty range of the original data.The latter applies the sequential Gaussian simulation(SGS)technique to stochastically interpolate geological variables,producing various possible spatial distributions to reflect the propagation of estimation errors and spatial variability.As excavation progresses,new geological information is continuously incorporated into the framework to revise and update prior knowledge.In this process,the data uncertainty in regional and tunnel face information is integrated using Bayesian Inference(BI)to update the probabilistic distribution of geological interfaces.The methodological uncertainty is addressed using the Minimum cross-entropy(MCE)principle,which optimizes the distribution while preserving global probabilistic characteristics and ensuring consistency with new information.Furthermore,the updated uncertainty analysis results are integrated into rock mass quality evaluation,leading to the development of an improved G-RMR classification system that incorporates a geological local variability index.To verify the engineering applicability and effectiveness of the proposed method,a case study was conducted on the Longtou Mountain Tunnel in Guangzhou,China.The results show that the regional multi-source uncertainty analysis reveals the spatial variability and fluctuation intensity of the geological structure.Following the update,uncertainty regarding the stratigraphic interface position within the local area is significantly reduced,with variance generally decreasing by approximately 40％-70％,while remaining robust under complex geological conditions.The G-RMR classification results are consistent with on-site adjustments and exhibit heightened sensitivity to variations in surrounding rock,providing a reliable reference for risk identification and supporting optimization during the construction stage.
To validate the proposed theory,a series of similarity model tests were conducted using a self-developed simulation system designed to assess the damage effects of deep underground chambers.This system reproduces the entire process of"in-situ stress loading+excavation unloading+planar shock wave disturbance."The test results demonstrate that:(1)Under the action of long stress waves,the failure mode of underground chambers aligns with that observed under static loads,characterized by slabbing buckling of the sidewalls rather than roof spalling;(2)The surrounding rock pressure calculated using the quasi-static method closely matches the measured values,confirming the reliability of the proposed model;(3)The plastic zone formed by excavation retains residual bearing capacity even under dynamic disturbances.This work elucidates the slabbing failure mechanism of deep underground chambers subjected to long-wave ground shocks,establishes a calculation method for surrounding rock pressure applicable to this working condition,and provides a theoretical foundation for the design and evaluation of deep underground protective engineering.
To meet the intelligent control requirements for curtain grouting in limestone dam foundations,this study proposes a dynamic prediction method that integrates Grouting Energy Intensity(GEI)with machine learning,aiming to enhance process precision and adaptability in complex karst strata.Utilizing field data from the Dehou Reservoir and the Dongzhuang Water Control Project,a grouting database was established,incorporating key parameters such as grouting pressure(P),flow rate(Q),and Lugeon value(q).A P-Q time-series prediction model was developed using machine learning algorithms to forecast future grouting parameters dynamically.The results indicate that the incorporation of GEI significantly enhances the model's coefficient of determination(R2).Additionally,a four-level rock mass permeability classification system based on Lugeon values and unit cement consumption was constructed,facilitating intelligent parameter matching and adaptive process control.This research offers a practical technical framework for intelligent construction and quality assurance in curtain grouting within karst regions.
