Search Results (80)

This study focuses on tunnel construction in fault fracture zones and systematically investigates the energy evolution and damage catastrophe mechanisms of surrounding rock during excavation, based on energy conservation principles and cusp catastrophe theory. A tunnel instability prediction and support optimization framework integrating energy damage evolution and intelligent optimization algorithms was developed. Field tests, rock mechanics experiments, and Discrete Fracture Network (DFN) numerical simulations reveal the intrinsic relationships among energy input, dissipation, damage accumulation, and instability under complex geological conditions. Particle Swarm Optimization–Back Propagation (PSO-BP) is applied to optimize tunnel support parameters. Model performance is evaluated using the Mean Absolute Error (MAE), Mean Squared Error (MSE), Mean Absolute Percentage Error (MAPE), and R-squared (R²). The results show that upon reaching structural mutation zones, the system damage variable (ds), displacement, and dissipated energy increase abruptly, indicating critical instability. Numerical simulation and catastrophe feature analysis demonstrate that energy-related damage accumulation is effectively suppressed, the system damage variable decreases significantly, and crown stability is greatly enhanced. These findings provide a theoretical basis and practical reference for optimizing tunnel support design and controlling instability risks in complex geological settings. Full article

Tunneling in fractured zones significantly affects surface and building deformation. This paper investigates the deformation of overlying buildings and the surrounding ground induced by multi-line TBM tunneling in fractured zones of the Qingdao Metro, combining a 3D physical model test, numerical simulations, and field monitoring to analyze the evolution of settlement and structural responses. The results show that settlement induced by TBM excavation peaks at the center and diminishes laterally, with amplified differential settlement and building torsion near fractured zones. Comparative analyses of reinforcement strategies indicate that crown grouting is the most effective in reducing deformation. Sensitivity analysis further indicates that tunnel depth, grouting pressure, and building–tunnel relative position are the dominant factors influencing building settlement. The findings provide practical guidance for similar projects in complex geological conditions and contribute to deformation control in underground works. Full article

This study investigates the seismic fragility of railway tunnels intersecting fractured geological zones using a nonlinear numerical approach. A series of dynamic analyses was performed on tunnel models subjected to multiple ground motions with varying frequency contents. The structural response was evaluated in terms of maximum bending moment, and the resulting damage indices were used to classify damage states. Based on these classifications, seismic fragility functions were developed for tunnels passing through fractured zones using a lognormal cumulative distribution with peak ground acceleration (PGA) as the intensity measure. The fragility curves indicated that the probabilities of exceeding minor, moderate, and extensive damage states surpassed 50% at PGAs of approximately 0.289 g, 0.578 g, and 0.91 g, respectively. These findings highlight the elevated seismic risk in tunnels intersecting fractured ground and emphasize the necessity of incorporating geological conditions into seismic design frameworks. Full article

To address the challenge of determining the borehole layout scheme in the practical application of high-pressure gas expansion rock breaking, this study takes the excavation of the safety passage at Kaixuan Road Station on the North Extension Line 2 of Chongqing Metro Line 18 as the engineering background. The rock-breaking capacity was evaluated by analyzing the damaged zone volume caused by gas expansion using FLAC3D 6.0 numerical simulation software, and vibration monitoring was conducted for the historical buildings on the surface. This study revealed the following: (1) When the borehole depth is 1.2 m and the charge length is 0.6 m, the optimal angle is 70°, with the optimal vertical and horizontal spacing between holes being 1200 mm and 2000 mm, respectively. (2) The numerical simulations indicated that by adjusting the charge density, the optimized sandstone borehole network parameters could be applied to mudstone strata, and the rock-breaking effect was similar. The difference in the volume of the damaged zones obtained in the two strata was less than 3%. (3) The vibration analysis demonstrated that the peak particle velocity generated by high-pressure gas expansion rock fracturing at the ancient building directly above was 0.06316 cm/s, which was lower than the threshold value of 0.1 cm/s and approximately 67.95% lower than that of explosive blasting. Furthermore, when the tunnel depth exceeded 29 m, the vibration velocity of surface structures remained within the safety range. The results verified the feasibility of applying the same borehole network parameters to different strata, providing theoretical support for the practical application of high-pressure gas expansion rock fracturing technology in engineering projects. Full article

In the mining of deep mineral resources and tunnel engineering, the degradation of mechanical properties and the evolution of energy of through-double-joint sandy slate under triaxial loading and unloading conditions are key scientific issues affecting the stability design of the project. The existing research has insufficiently explored the joint inclination angle effect, damage evolution mechanism, and energy distribution characteristics of this type of rock mass under the path of increasing axial pressure and removing confining pressure. Based on this, in this study, uniaxial compression, conventional triaxial compression and increasing axial pressure, and removing confining pressure tests were conducted on four types of rock-like materials with prefabricated 0°, 30°, 60°, and 90° through-double-joint inclinations under different confining pressures. The axial stress/strain curve, failure characteristics, and energy evolution law were comprehensively analyzed, and damage variables based on dissipated energy were proposed. The test results show that the joint inclination angle significantly affects the bearing capacity of the specimen, and the peak strength shows a trend of first increasing and then decreasing with the increase in the inclination angle. In terms of failure modes, the specimens under conventional triaxial compression exhibit progressive compression/shear failure (accompanied by rock bridge fracture zones), while under increased axial compression and relief of confining pressure, a combined tensioning and shear failure is induced. Moreover, brittleness is more pronounced under high confining pressure, and the joint inclination angle also has a significant control effect on the failure path. In terms of energy, under the same confining pressure, as the joint inclination angle increases, the dissipated energy and total energy of the cemented filling body at the end of triaxial compression first decrease and then increase. The triaxial compression damage constitutive model of jointed rock mass established based on dissipated energy can divide the damage evolution into three stages: initial damage, damage development, and accelerated damage growth. Verified by experimental data, this model can well describe the damage evolution characteristics of rock masses with different joint inclination angles. Moreover, an increase in the joint inclination angle will lead to varying degrees of damage during the loading process of the rock mass. The research results can provide key theoretical support and design basis for the stability assessment of surrounding rock in deep and high-stress plateau tunnels, the optimization of support parameters for jointed rock masses, and early warning of rockburst disasters. Full article

Crack initiation, propagation, and slippage serve as the key mesoscopic mechanisms contributing to the deterioration of deep tunnel surrounding rocks. In this study, a secondary anisotropy of deep tunnels surrounding rocks was proposed: The axial-displacement constraint of deep tunnels forces cracks in the surrounding rock to initiate, propagate, and slip in planes parallel to the tunnel axial direction. These cracks have no significant effect on the axial strength of the surrounding rock but significantly reduce the tangential strength, resulting in the secondary anisotropy. First, the secondary anisotropy was verified by a hybrid stress–strain controlled true triaxial test of sandstone specimens, a CT 3D (computed tomography three-dimensional) reconstruction of a fractured sandstone specimen, a numerical simulation of heterogeneous rock specimens, and field borehole TV (television) images. Subsequently, a novel SSA (strain-softening and secondary anisotropy) constitutive model was developed to characterise the secondary anisotropy of the surrounding rock and developed using C++ into a numerical form that can be called by FLAC^3D (Fast Lagrangian Analysis of Continua in 3 Dimensions). Finally, effects of secondary anisotropy on a deep tunnel surrounding rock were analysed by comparing the results calculated by the SSA model and a uniform strain-softening model. The results show that considering the secondary anisotropy, the extent of strain-softening of the surrounding rock was mitigated, particularly the axial strain-softening. Moreover, it reduced the surface displacement, plastic zone, and dissipated plastic strain energy of the surrounding rock. The proposed SSA model can precisely characterise the objectively existent secondary anisotropy, enhancing the accuracy of numerical simulations for tunnels, particularly for deep tunnels. Full article

Existing risk assessment approaches for soft rock tunnels in fault-fractured zones typically employ single weighting schemes, inadequately integrate subjective and objective weights, and fail to define clear risk. This study proposes a risk-grading methodology that integrates an enhanced game theoretic weight-balancing algorithm with an optimized cloud entropy extension cloud model. Initially, a comprehensive indicator system encompassing geological (surrounding rock grade, groundwater conditions, fault thickness, dip, and strike), design (excavation cross-section shape, excavation span, and tunnel cross-sectional area), and support (support stiffness, support installation timing, and construction step length) parameters is established. Subjective weights obtained via the analytic hierarchy process (AHP) are combined with objective weights calculated using the entropy, coefficient of variation, and CRITIC methods and subsequently balanced through a game theoretic approach to mitigate bias and reconcile expert judgment with data objectivity. Subsequently, the optimized cloud entropy extension cloud algorithm quantifies the fuzzy relationships between indicators and risk levels, yielding a cloud association evaluation matrix for precise classification. A case study of a representative soft rock tunnel in a fault-fractured zone validates this method’s enhanced accuracy, stability, and rationality, offering a robust tool for risk management and design decision making in complex geological settings. Full article

This study proposes an intelligent prediction framework integrating native sparse attention (NSA) with the Chen-Guan (CHG) algorithm to optimize tunnel boring machine (TBM) operations in heterogeneous geological environments. The framework resolves critical limitations of conventional experience-driven approaches that inadequately address the nonlinear coupling between the spatial heterogeneity of rock mass parameters and mechanical system responses. Three principal innovations are introduced: (1) a hardware-compatible sparse attention architecture achieving O(n) computational complexity while preserving high-fidelity geological feature extraction capabilities; (2) an adaptive kernel function optimization mechanism that reduces confidence interval width by 41.3% through synergistic integration of boundary likelihood-driven kernel selection with Chebyshev inequality-based posterior estimation; and (3) a physics-enhanced modelling methodology combining non-Hertzian contact mechanics with eddy field evolution equations. Validation experiments employing field data from the Pujiang Town Plot 125-2 Tunnel Project demonstrated superior performance metrics, including 92.4% ± 1.8% warning accuracy for fractured zones, ≤28 ms optimization response time, and ≤4.7% relative error in energy dissipation analysis. Comparative analysis revealed a 32.7% reduction in root mean square error (p < 0.01) and 4.8-fold inference speed acceleration relative to conventional methods, establishing a novel data–physics fusion paradigm for TBM control with substantial implications for intelligent tunnelling in complex geological formations. Full article

Tunnel deformation induced by excavation in brittle and quasi-brittle rock masses involves complex interactions among stress redistribution, plastic deformation, and fracture evolution. Existing numerical approaches often struggle to capture these coupled mechanisms, particularly under varying material properties such as Poisson’s ratio. This study aims to analyze tunnel deformation using an elastoplastic Discretized Virtual Internal Bond (DVIB) method embedded in a modified Stillinger–Weber (SW) potential. In this framework, plastic deformation is introduced through the two-body component, whereas the three-body angular potential governs Poisson’s ratio. A fracture-energy-based regularization strategy was implemented to reduce the mesh sensitivity and ensure energy consistency during bond failure. The model was evaluated through numerical simulations, including pre-cracked plates, center-split circular Brazilian discs, and tunnel models, under various in situ stress conditions and Poisson ratios. The findings indicate that higher Poisson’s ratios lead to increased deformation, with tunnel wall displacements rising from 0.45 mm at $\nu =0.17 \mathrm{to} 1.32 \mathrm{mm}$ at $\nu =0.35$. The deformation patterns and failure zones are consistent with theoretical expectations, confirming the applicability of the model to tunnel stability analysis in brittle geomaterials. Full article

To address the challenge of dynamic monitoring during grouting operations in coal mine fault zones under pressurized mining, this study proposes the Borehole–Tunnel Joint Resistivity Method (BTJRM). By integrating three-dimensional (3D) electrode arrays in both tunnels and boreholes with 3D resistivity inversion technology, this approach enables fully automated underground data acquisition and real-time processing, facilitating comprehensive dynamic monitoring of grout propagation. A case study was conducted on a coal mine fault grouting project, where tunnel and borehole survey lines were deployed to construct a 3D cross-monitoring network, overcoming the limitations of traditional 2D data acquisition. Finite volume method and quasi-Gauss–Newton inversion algorithms were employed to analyze dynamic resistivity variations, enhancing spatial resolution for detailed characterization of grout migration. Key findings include: (1) Grout diffusion reduced resistivity by 10%, aligning with electrical response patterns during fracture-filling stages; (2) 3D inversion reveals that grout propagates along the principal stress axis, forming a “Y”-shaped low-resistivity anomaly zone that penetrates the fault structural block and extends into roadway areas. The maximum planar and vertical displacements of grout reach 100 m and 40 m, respectively. Thirty days post-grouting, resistivity recovers by up to 22%, reflecting the electrical signature of grout consolidation; (3) This method enables 3D reconstruction of grout diffusion pathways, extends the time window for early warning of water-conducting channel development, and enhances pre-warning capabilities for grout migration. It provides a robust framework for real-time sealing control of fault strata, offering a novel dynamic monitoring technology for mine water inrush prevention. The technology can provide reliable grouting evaluation for mine disaster control engineering. Full article

In the operation period of long-distance water delivery tunnels, safety may be impacted by the risks that arise from different aspects including the complex geological conditions with fault fracture zones and karst caves, the diverse environment affecting structural safety and stability, and the construction defects of tunnels. It is crucial to assess and mitigate potential risks to ensure operation safety. To address this challenge, this study presents a systemic risk assessment for the operation safety of a real project of a water delivery tunnel. The potential risks of this project were first summarized based on the analytical hierarchy process (AHP), and a model that integrates the AHP and fuzzy comprehensive evaluation (FCE) was built to effectively quantify and categorize risks for the project in its operation stage. Results of the assessment indicate that the risk of this tunnel operation can be classified at a moderate grade with a calculted specific risk score of 43.935, with the high-risk factors including segment lining cracking, flow control, and regular maintenance. In response to the high-risk factors, the preventative and control measures are proposed to guide effective risk management. The model presented offers an efficient risk assessment tool for water delivery tunnels, aiding decision makers making more rational management decisions in complex and uncertain environments. Full article

In order to control the stability of tunnel surrounding rock, reduce the construction cost, and improve the construction schedule, the deformation behavior and instability mechanisms of tunnel surrounding rock are studied by numerical simulation and field monitoring methods according to the engineering characteristics of the fractured slate zone under construction of Longshu Tunnel in the central Yunnan water diversion project. The results show that step excavation technology can effectively control the deformation of the tunnel surrounding rock. The deformation range of the top and bottom of the tunnel is 32 mm~35 mm, the deformation range of the left shoulder is 25 mm~28 mm, and the deformation range of the right shoulder is 26 mm~29 mm. The stability range of the tunnel surrounding rock is about 25 m away from the palm surface, and the concentrated stress on both sides of the tunnel is at a low level. Full article

Permanent displacements caused by active faults can lead to the severe deformation of tunnel liners. To investigate the effect of fault fracture deformation patterns on the deformation of tunnel liners under fault dislocation, this paper categorized three fault-zone fracture deformation patterns and conducted numerical simulations for tunnel’s surrounding rock-liner systems under different fracture deformation patterns. Furthermore, the longitudinal displacement, relative deformation, axial stress, and shear stress of the tunnel liner were measured to characterize the mechanical response of the tunnel, and the effects of fault geometric parameters on the mechanical response of the tunnel liner were explored. The results showed that fracture deformation patterns were broadly categorized into uniform fracture deformation, linear fracture deformation, and nonlinear fracture deformation patterns. The distribution patterns of tunnel liner stress and deformation under these fracture deformation patterns were similar, but the magnitude of the peaks and the intensity of their effects differed. Under reverse fault dislocation, the peak values of tunnel liner deformation and shear stress occurred at the rupture plane. In contrast, the maximum axial stress was observed at the interface between soft and hard rock masses. When the core width of the fault zone decreased and the fault dip direction increased, the intensity of the mechanical response of the tunnel liner increased. With the fault dip decreased, the axial stress in the tunnel liner transitions from tensile-compressive stress to compressive stress, the shear stress decreases, and the intensity of the relative deformation of the tunnel liner increases. These research results can provide significant guidelines for tunnel design crossing the reverse fault. Full article

Preliminary tunnel surveys are essential for identifying geological hazards such as aquifers, faults, and karstic zones. While first-arrival tomography is effective for imaging shallow anomalies, traditional seismic sources face significant limitations in forested mountainous regions due to mobility, cost, and environmental impact. To address this, we deployed a seismic source delivered by an unmanned aerial vehicle (UAV) for a highway tunnel survey in Lijiang, China. The UAV system, paired with nodal geophones, enabled rapid, low-impact, and high-resolution data acquisition in rugged terrain. To enhance the weak far-offset refractions affected by near-surface attenuation, we applied supervirtual refraction interferometry (SVI), which significantly improved the signal-to-noise ratio and expanded the usable first-arrival dataset. The combined use of UAV excitation and SVI processing produced a high-precision P-wave velocity model through traveltime tomography, aligned well with borehole data. This model revealed the spatial distribution of weathered zones and bedrock interfaces, and allowed us to infer potential fracture zones. The results offer critical guidance for tunnel alignment and hazard mitigation in complex geological settings. Full article

This study proposes a novel drone-based semi-airborne total-field magnetometric resistivity (SA-TFMMR) system for high-resolution detection of conductive fracture zones in geologically hazardous terrains. The system integrates a high-power, low-frequency grounded-wire transmitter with a drone-mounted total-field magnetometer, achieving high survey efficiency and extensive data coverage in mountainous areas. We develop a 3D inversion framework incorporating terrain-adaptive depth weighting, which successfully images a dipping water-saturated fracture zone model beneath a reservoir overburden at a tunnel water gushing accident site. Sensitivity analyses of SA-TFMMR reveal that the effectiveness of detection is controlled by the source-target coupling and the orientation of the target body with respect to the geomagnetic field. Optimal current injection along target strike directions amplifies magnetic anomalies, and orthogonal multi-source configurations can enhance imaging resolution. This UAV-geophysical integration provides a paradigm for pre-disaster monitoring of water-related geohazards. Full article