Search Results (119)

Traditional manual inspection methods for tunnel lining leakage are subjective and inefficient, while existing models lack sufficient recognition accuracy in complex scenarios. An intelligent leakage identification model adaptable to complex backgrounds is therefore needed. To address these issues, a Vision Transformer (ViT) was integrated into the UNet architecture, forming an SE-TransUNet model by incorporating SE-Block modules at skip connections between the encoder-decoder and the ViT output. Using a hybrid leakage dataset partitioned by k-fold cross-validation, the roles of SE-Block and ViT modules were examined through ablation experiments, and the model’s attention mechanism for leakage features was analyzed via Score-CAM heatmaps. Results indicate: (1) SE-TransUNet achieved mean values of 0.8318 (IoU), 0.8304 (Dice), 0.9394 (Recall), 0.8480 (Precision), 0.9733 (AUC), 0.8562 (MCC), 0.9218 (F1-score), and 6.53 (FPS) on the hybrid dataset, demonstrating robust generalization in scenarios with dent shadows, stain interference, and faint leakage traces. (2) Ablation experiments confirmed both modules’ necessity: The baseline model’s IoU exceeded the variant without the SE module by 4.50% and the variant without both the SE and ViT modules by 7.04%. (3) Score-CAM heatmaps showed the SE module broadened the model’s attention coverage of leakage areas, enhanced feature continuity, and improved anti-interference capability in complex environments. This research may provide a reference for related fields. Full article

Cylindrical retaining structures are widely adopted in intercity railway tunnel engineering due to their exceptional load-bearing performance, no need for internal support, and efficient utilization of concrete compressive strength. Measured deformation data not only comprehensively reflect the influence of construction and hydrogeological conditions but also directly and clearly indicate the safety and stability status of structure. Therefore, based on two geometrically similar cylindrical shield tunnel shafts in Shenzhen, the surface deformation, structure deformation, and changes in groundwater outside the shafts during excavation were analyzed, and the deformation characteristics under the soil–rock composite stratum were summarized. Results indicate that the uneven distribution of surface surcharge and groundwater level are key factors causing differential deformations. The maximum horizontal deformation of the shafts wall is less than 0.05% of the current excavation depth (H), occurring primarily in two zones: from H − 20 m to H + 20 m and in the shallow 0–10 m range. Vertical deformations at the wall top are mostly within ±0.2% H. Localized groundwater leakage in joints may lead to groundwater redistribution and seepage-induced fine particle migration, exacerbating uneven deformations. Timely grouting when leakage occurs and selecting joints with superior waterproof sealing performance are essential measures to ensure effective sealing. Compared with general polygonal foundation pits, cylindrical retaining structures can achieve low environmental disturbances while possessing high structural stability. Full article

Pipeline leakage can induce ground surface settlements and structural responses in existing tunnels. A thorough understanding of pipeline–tunnel interactions is crucial for optimizing urban underground design and establishing construction guidelines. As urban underground spaces undergo rapid, large-scale development, their layouts have grown increasingly complex. Previous studies have mainly focused on the leakage propagation range and the resulting strata instability during tunnel excavation, while paying limited attention to the effects of pipeline leakage on existing tunnels. This study systematically investigated the mechanical response of existing tunnel structures to pipeline leakage under different layout configuration conditions using numerical modeling. A two-dimensional numerical model was developed to simulate the pipeline leakage process and its impact on adjacent tunnels. The research established a correlation between surrounding rock strength parameters and the saturation degree while examining the evolution patterns of leakage effects in various tunnel–pipeline arrangements. The analysis specifically focused on the mechanical influence of horizontal pipeline–tunnel distance, quantitatively determining the relationships among pipeline–tunnel spacing, leakage duration, and structural internal force. The horizontal pipeline–tunnel distance did not influence the development of the leakage zone above the tunnel vault but significantly altered the seepage path length and interface contact area. The complete encapsulation of the tunnel periphery by the leakage zone required progressively longer durations with increasing horizontal offsets: 16 days (0 m), 20 days (3 m), and 33 days (6 m). Corresponding circumferential contact ratios at 10 days were measured at 68.9%, 56.4%, and 30.6%, respectively. Furthermore, prolonged seepage duration led to increased ground subsidence with expanded affected areas, while the maximum settlement decreased proportionally with greater horizontal separation from the tunnel. These findings provide valuable insights for planning, designing, and maintaining “old tunnel-new pipeline” systems in urban underground development. Full article

[Objective] This study aims to assess and predict the risks of water inrush and leakage during tunnel excavation in karst regions, where groundwater intrusion poses serious threats to construction safety and long-term hydrogeological sustainability. [Study area] This study is conducted in the Qigan Mountain, involving detailed hydrogeological surveys and hydrochemical analyses to understand the subsurface conditions. [Methods] Numerical simulation methods are employed to model the regional seepage field distribution under natural conditions and two excavation conditions, using MODFLOW. [Challenges] One of the main challenges is accurately estimating tunnel water inflow under varying geological and hydrological conditions. [Results] The simulation results indicate that under excavation with blocking conditions, tunnel water inflow reaches 31,932 m³/d, whereas without blocking, inflow surges to 359,199 m³/d. In contrast, the theoretical calculation estimates a water inflow of 131,445 m³/d, revealing considerable discrepancies between the methods. [Recommendations] These findings highlight an important point of reference for the prevention of water influx in karst tunnel construction. Full article

The reduction in the stability of rock slopes due to rainfall is a significant issue in tropical regions. Unsaturated soil, commonly found on hill slopes, provides higher shear strength compared to saturated soil due to matric suction. Soil moisture plays a crucial role in determining slope stability during rainfall events, yet it is often overlooked in geotechnical engineering projects. This study integrates both steady-state and transient analyses to examine how rainfall intensity affects the stability of a rock slope near a tunnel portal. Transient seepage analysis was conducted using SEEP/W to simulate changes in pore water pressure (PWP) resulting from rainfall infiltration under historical and future precipitation conditions. The analysis considers medium (SSP245) and worst-case (SSP585) climate change scenarios as per Coupled Model Intercomparison Project Phase 6 (CMIP6). The findings underscore the significant impact of rainfall-induced infiltration on slope stability and highlight the importance of incorporating soil moisture dynamics in slope stability assessments. The safety factor, initially 1.54 before accounting for rainfall effects, decreases to 1.34 when the effects of rainfall are included. Full article

Deep-buried subsea tunnels are often under high water pressure conditions, and the influence of the seepage field on the tunnel cannot be ignored. Existing studies generally assume that the surrounding rock exhibits permeability isotropy; this study developed a model of deep-buried subsea tunnel that considers the permeability anisotropy of surrounding rock and investigated the effects of permeability differences between the surrounding rock and lining structure on tunnel seepage flow and plastic zone extent. By employing coordinate transformation and conformal mapping methods, the hydraulic head and the seepage discharge for each region are determined for each section of the tunnel. Based on the analytical solution of the seepage field, the seepage force is treated as a body force, and using the Mohr–Coulomb criterion, an elastoplastic analytical solution for the lining and surrounding rock under anisotropic seepage is derived. Using the Shenzhen MaWan Sea-Crossing Passage as a case study, numerical simulations are conducted using Abaqus2021, and the results are compared with the analytical solution to verify the accuracy of the study. The research shows that the permeability anisotropy of surrounding rock increases the seepage discharge, and this effect becomes more significant with increasing burial depth. If the anisotropy is 10 times greater than its previous value, the tunnel seepage volume will increase by 35.6%. When the surrounding rock permeability is sufficiently large, the impact of permeability anisotropy on the seepage discharge is relatively weak, with the seepage discharge primarily dominated by the permeability of the lining. In the tunnel stress field, due to the significant difference in stiffness between the lining and the surrounding rock, the hoop stress in the lining is much larger than that in the surrounding rock, and there is a stress discontinuity at their interface. When the permeability of the elastic zone of the surrounding rock is 100 times greater than that of the plastic zone, the plastic radius of the tunnel will increase by 2 to 3 times compared to the previous value. Reducing the permeability of the plastic zone in the surrounding rock effectively limits the seepage body force acting on the lining, thereby enhancing the stability of the lining structure and reducing the risk of damage to the tunnel. Full article

The seepage caused by heavy rainfall and storm runoff is not a static phenomenon. On the contrary, it is a dynamic process known as unsaturated transient seepage. Under the condition, the spatiotemporal variations in suction stress cannot be overlooked. With the development of tunnel mechanics, there has been an emergence of tunnels affected by high ground temperatures or temperature influences, highlighting the necessity of incorporating temperature effects into the analysis. This article proposes a new framework for the spatiotemporal response of tunnel face safety to temperature-affected and unsaturated transient seepage conditions. A one-dimensional transient seepage assumption is used to develop an analytical model describing unsaturated transient seepage, which is then integrated centered on suction stress strength theory for unsaturated soils to acquire suction stress variations with depth and time. The temperature impact on the unsaturated soil shear strength is incorporated, applying a temperature-sensitive effective stress model in conjunction with the soil–water characteristic curve to quantitatively analyze temperature-induced apparent cohesion changes. The 3D logarithmic spiral failure model is used to analyze the tunnel face stability. The validity of the proposed failure model is demonstrated through an engineering calculation. The rates of internal dissipation and external work are calculated, and a kinematic approach related to strength reduction is used to determine the safety factor of the tunnel face with zero support pressure. The results show that considering transient unsaturated seepage and temperature effects can increase the safety factor. The influence of these effects mainly depends on the soil type, tunnel geometric parameters, and seepage conditions. This work explores the influence of variations in a series of parameters on the failure mode of tunnel faces under temperature effects, taking into account unsaturated transient seepage, thereby providing valuable references for the design and construction of tunnels in the future. Full article

Using COMSOL finite element software, a three-dimensional numerical transient model of an underground tunnel collapse vertical freezing repair project was established. The model was altered to change the head difference, allowing for analysis of the development of the permafrost curtain, the time of intersection circles, and the freezing temperature field cloud diagram. The results indicated that, without seepage, development of the upstream and downstream permafrost curtains was stable and uniform. However, under seepage conditions, development of the upstream and downstream permafrost curtains became increasingly uneven with increasing seepage velocity. The downstream side of the soil body began freezing earlier than the upstream side, and the final temperature was lower. The intersection time of the freezing wall was an important indicator of development of the permafrost curtain, and the freezing time of the freezing wall was the most critical indicator. A hydraulic head difference of 1 m was found to significantly impact the development of the freezing wall, with less influence from seepage velocity on the overall permafrost curtain intersection time. However, the intersection time of the isotherm increased significantly with increasing seepage flow rate. The findings from this project provide a theoretical reference for future restoration design. Full article

To prevent a decrease in the water level of the reservoir caused by water surges and seepage from the tunnel beneath the reservoir, it is essential to clarify the hydraulic connection between the reservoir and the underpass tunnel. A MODFLOW three-dimensional grid model was developed using GMS 10.6 software to examine this hydraulic connection. The model focused on the section of the tunnel beneath the reservoir, investigating the effects of factors such as the permeability coefficient of the stratum, rainfall recharge, fault permeability, aquifer thickness, and the silt layer at the reservoir’s bottom on tunnel water inflow. Additionally, the relationship between tunnel water inflow and reservoir water levels was analyzed. The results indicate that the presence of faults enhances the hydraulic connection between the tunnel and the reservoir. An increase in fault permeability leads to greater water inflow into the tunnel at the fault location. As the permeability coefficient of the stratum increases, the decline in reservoir water levels follows an S-shaped curve. The silt layer at the bottom of the reservoir helps mitigate the drop in water levels caused by tunnel water inflow. When the water influx is below 0.4 m³/d, the reservoir water level remains unaffected. However, when the influx exceeds 0.7 m³/d, the water level decreases rapidly as the influx increases. At an influx near 1 m³/d, the reservoir level drops by approximately 7 m. The reservoir is particularly susceptible to leakage when the fault penetrates the bottom of the reservoir and forms a hydraulic connection with the tunnel. This study provides a predictive method for assessing reservoir water level reductions caused by tunnel surges, which can aid in mitigating such effects in the future. Full article

The phenomenon of tunnel erosion is quite common in the Loess Plateau. Tunnel erosion can cause disasters such as landslides, mudslides, and ground collapses, resulting in significant economic losses and posing a threat to people’s safety. Therefore, understanding the evolution mechanism of tunnel erosion not only helps to analyze and predict the development law of erosion but also has a certain guiding role in engineering activities. Many scholars (including our team) have conducted field investigations and statistical analysis on the phenomenon of tunnel erosion in loess; however, these studies still have shortcomings in visual quantitative analysis. The combination of the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD) has significant advantages in studying soil seepage and erosion. Based on existing experimental research, this article combines the Discrete Element Method (DEM) with Computational Fluid Dynamics (CFD) to establish a CFD-DEM coupled model that can simulate tunnel erosion processes. In this model, by changing the working conditions (vertical cracks, horizontal cracks, and circular holes) and erosion water pressure conditions (200 Pa, 400 Pa, 600 Pa), the development process of tunnel erosion and changes in erosion rate are explored. The results indicate that during the process of fluid erosion, the original vertical crack, horizontal crack, and circular hole-shaped tunnels all become a circular cave. The increase in erosion water pressure accelerates the erosion rate of the model, and the attenuation rate of the particle contact force chain also increases, resulting in a decrease in the total erosion time. During the erosion process, the curve of the calculated erosion rate shows a pattern of slow growth at first, then rapid growth, before finally stabilizing. The variation law of the erosion rate curve combined with the process of tunnel erosion can roughly divide the process of tunnel erosion into three stages: the slow erosion stage, the rapid erosion stage, and the uniform erosion stage. Full article

With the increasing number of anti-seepage reinforcement projects and the continuous improvement of quality requirements, high-performance and green requirements have also been put forward for grouting materials. Traditional karst cave grouting mainly uses cement-based grouting materials, which not only have high carbon emissions but also do not comply with the sustainable development strategy with regard to being green, low-carbon, and environmentally friendly. A green grouting material made by mixing a slurry A and slurry B is proposed in this paper. The solid phase of slurry A is composed of stone powder and bentonite, for which an anti-washout admixture is necessary. Slurry B is a suspension of thickener (CMC or HPMC) and anhydrous ethanol. By mixing the two slurries evenly, the grouting material is obtained. Experiments were used to investigate the ideal ratios of stone powder, bentonite, and water in slurry A, and the ratio of thickener to anhydrous ethanol in slurry B, and to analyze the development and evolution of the apparent viscosity of slurry A and slurry B after mixing. This study revealed that the optimum ratio of stone powder and bentonite was 4:1, and the most reasonable water–solid ratio was 0.8:1.0. The optimum ratio of anhydrous ethanol to CMC or HPMC in slurry B was 5:1. Slurry B was added to slurry A at a rate of 5~10% to obtain the best grouting material properties. The proposed mixed grouting material would not disperse even in flowing water and could harden and consolidate quickly. The strength of the consolidation grouting body was close to that of wet soil, which can meet requirements for tunnel construction. Full article

This paper aims to estimate the stability of tunnel faces in inclined layered soils under steady unsaturated seepage conditions, comparing the degree of correlation between the stability of the tunnel face and the influence of three types of parameters: unsaturated soil parameters, spatial geometric parameters of soil stratification, and other relevant factors. The study leverages the suction head distribution in multi-layered unsaturated soils, deriving a new formula to compute the effects of steady-state seepage forces with matric suction distribution in inclined stratified soil layers. A three-dimensional discrete rotational failure mechanism model is employed to calculate the critical support force at the tunnel face. The corresponding parametric analysis involves unsaturated soil parameters, spatial geometric parameters, and the variations in these parameters across different soil layers. Based on this analysis, the varying degrees of correlation between tunnel stability and changes in spatial angle parameters considering soil stratification, and the variations in unsaturated parameters across different soil layers are thoroughly investigated. The proposed framework serves as a valuable tool for quantitatively assessing the effects of unsaturated seepage forces on the stability of tunnel faces situated within complex, inclined, layered soil formations. Full article

Three-dimensional numerical simulation of subsurface flow dynamics in karst conduits at dam sites represents a pivotal component of hydrogeological research, essential for unraveling the intricate behavior of water movement within karstified terrains. This study introduces a novel approach for accounting for the presence of karst conduits and presents a comprehensive three-dimensional flow simulation for the dam site of the Jingxian Pumped Storage Hydropower Plant. This method reduces mesh division, simplifies calculations, and improves model convergence. The findings reveal that the numerical model adeptly captures the declining groundwater levels within the study area, with enhanced precision achieved through the utilization of COMSOL’s Line Mass Source feature. By representing leakage tunnel cylinders as edges, the model significantly improves meshing efficiency, circumventing the computational burden associated with the explicit resolution of intricate geometric details. In the absence of remedial measures, the simulation predicts that groundwater will preferentially drain downstream via two distinct leakage pathways at the dam’s base, presenting a potential threat to the structural integrity and operational stability of the project. To address this risk, the implementation of robust seepage control measures is imperative. Once these measures are established, the dam is expected to function as an effective hydraulic barrier, ensuring the long-term stability and operational efficacy of the hydropower plant. Full article

Tunnel excavation in water-rich and saturated loess layers often encounters a series of engineering disasters, including surface settlement, large deformations of surrounding rock, collapses, water inrushes, mud inrushes, and lining cracks. This paper presents an analogy of 16 cases of instability and collapse of surrounding rock during the excavation of water-rich loess tunnels in China’s loess regions. The weight of influence of various factors affecting the stability of surrounding rocks has been analyzed based on the Fuzzy Analytic Hierarchy Process (FAHP), addressing the engineering challenges encountered during the construction of the Tuanjie Tunnel. Measures such as deep well-point dewatering of the surface, reinforcement of locking foot anchors, and construction treatment with large arch feet are proposed. The effectiveness of these treatments is then monitored and analyzed. The results show that after 30 days of dewatering, the average water content of the surrounding rock decreased from 28.8% to 22.3%, transforming the surrounding rock from a soft plastic state to a hard plastic state. Phenomena such as mud inrushes at the tunnel face and water seepage through the lining are significantly reduced, and the self-stabilizing capacity of the surrounding rock is markedly improved. By optimizing the excavation method and enhancing support parameters, the construction progress rate for Grade VI surrounding rock has increased from 10–15 m per month to 40 m per month, validating the effectiveness of the proposed measures. Full article

Coal mine water hazards are one of the five major natural disasters in mines, and water in depleted areas is the most serious form of water hazard causing casualties. The exploration of depleted areas, especially old tunnels, presents significant challenges, and achieving the required borehole density for exploration in depleted areas is difficult in reality. The authors of this paper previously applied for a patent titled “Water Injection Exploration Method for Depleted Areas Based on Stress Seepage Principle”. In order to theoretically analyze the feasibility of the patented results and validate them in practice, we first analyze the stress distribution and seepage phenomena around the goaf theoretically, construct boreholes underground in Renlou Coal Mine, conducting on-site water injection tests for different zones (depleted areas, old tunnels, and general boreholes), and perform transient electromagnetic observations during the water injection tests. A total of 355 sets of water injection flow rate and pressure data were obtained from different zones in three different boreholes; permeability coefficients were calculated based on the measured data, and relevant diagrams were drawn. Through the analysis of water injection test data and theoretical analysis, the following conclusions were drawn: there are disturbances and stress reduction zones around depleted areas (old tunnels), and when the equivalent normal stress induced by water injection pressure is greater than zero, the permeability of fractures will increase significantly. Whether it is a borehole aimed at depleted areas or old tunnels, it shows the characteristic that the closer the distance to the depleted areas (old tunnels) is, the smaller the water injection pressure, and the larger the permeability coefficient. When water is injected into the disturbance and stress reduction zones of the depleted areas (old tunnels), the water injection pressure can decrease from 9–10 MPa to 3–4 MPa, and the permeability coefficient may even increase in quantity value. The phenomena of pressure reduction and increased permeability during water injection are significantly observable, indicating that the water injection exploration method for depleted areas based on the stress seepage principle is feasible and has practical significance. Full article