Tunnel Sidewall Research Articles

Enhancing Shear Strength of Weakly Consolidated Mudstone in Water-Diversion Tunnels Through Artificial Ground-Freezing Techniques: An Experimental and Theoretical Study

The utilization of artificial ground-freezing techniques is increasingly prevalent in the construction of water-diversion tunnels. The inadequate mechanical properties of weakly consolidated mudstone (WCM) pose significant challenges for tunneling construction. In this study, a series of triaxial shear tests were conducted on frozen specimens of WCM to elucidate its shear strength characteristics. The experiment involved four freezing temperatures (0, −5, −10, and −20 °C) and four confining pressures (1, 2, 3, and 4 MPa). The results indicate that the shear failure mode of the WCM exhibits distinct shear zone failure characteristics under artificial freezing conditions, particularly prominent in the lower temperature environments. As the freezing temperature gradually decreases, there is a substantial increase of over 200% in the shear strength of frozen specimens, accompanied by a corresponding decrease in yield strain. Furthermore, the cohesion and internal friction angle of frozen WCM increase as the freezing temperature decreases, following a complex exponential function relationship rather than a linear one. As the freezing temperature decreases from 0 °C to −20 °C, there is an increase in cohesion and internal friction angle from 1012 kPa to 1425 kPa, accompanied by a rise in the internal friction angle from 43.2° to 58.1°. Notably, the application of confining pressure exerts a pronounced influence on the shear strength of frozen WCM, with elevated levels of confining pressure resulting in a substantial augmentation of the shear strength. The failure mode of frozen WCM is significantly influenced by freezing temperatures. At low temperatures, the specimen of mudstone exhibits a shear failure behavior, while at high temperatures, it predominantly demonstrates expansion failure. This phenomenon can be attributed to the increased brittleness of specimens caused by ice crystals, rendering it more susceptible to brittle failure under shearing forces. These findings signify an enhancement in the mechanical behavior of WCM within the tunnel sidewall under artificial freezing conditions.

Experimental study on transverse fire source and blockage locations influence on tunnel fire temperature distribution

Previous research has commonly assumed that tunnel fire blockage occurs at the central longitudinal axis of tunnels. However, fires may arise at different points within tunnels, each with various distances from the tunnel sidewall. The study aimed to investigate the distribution of ceiling temperature fields across various scenarios of blockage and transverse fire source locations by conducting a sequence of fire experiments within a reduced-scale 1:10 horseshoe-shaped tunnel model. The findings indicate that at sufficiently low ventilation velocities (v’≤0.19), the maximum ceiling temperature rise in the tunnel remains virtually unchanged regardless of the locations of blockage and transverse fire source. For higher ventilation velocities (v’>0.19), the maximum ceiling temperature rise diminishes with greater blockage-fire source distance. Additionally, the maximum ceiling temperature rise increases as the distance between the sidewall and the fire source diminishes. Furthermore, a new model has been formulated to forecast the dimensionless maximum ceiling temperature rise, incorporating both blockage and transverse fire locations.

Exploring the causes of frequent accidents at highway tunnel exits: Coupling analysis of the slack effect and white hole effect in extra-long tunnels

In this paper, the causes of frequent traffic accidents at the exits of highway tunnels are investigated. This study recruited 34 subjects to conduct vehicle experiments using an illumination meter, eye tracker, Smarter Eye and OBD to measure the illumination, eye movement characteristics, driving trajectory, and speed while driving in a tunnel exit. A questionnaire was used to investigate drivers’ subjective feelings while driving. The change trend of each indicator in the area near the tunnel exit was analyzed, and the relationships among the light environment, driver physiology, driving behavior, and driver psychology were explored. The psychological and physiological inconsistency phenomenon and abnormal acceleration behavior were observed at the tunnel exit, and the slack effect was verified. As the tunnel exit area is driven through, with the rapid increase in illumination, the rate of change of the driver’s pupil area increases, and the distance between the vehicle and the tunnel sidewall increases. It is unreasonable that in a tunnel exit with a poor traffic environment, some drivers experience psychological slack and tend to increase their speed and accelerate out of the tunnel. The slack effect is observed in most drivers, approximately 79.4% of the total. The white hole effect interferes with drivers’ vision and reduces their ability to obtain traffic information. The slack effect reduces drivers’ attention and increases vehicle speed. A coupling effect exists between the white hole and slack effects, which together threaten traffic safety at the tunnel exit.

Driving Characteristics of Drivers Avoiding Lateral Obstacles in Mountain Highway Tunnels: A Dynamic Lateral Safety Distance Prediction Model

A natural driving real-vehicle test was conducted in nine tunnels in Chongqing, China. The driving trajectories and speeds of 40 drivers were recorded to better understand drivers’ driving characteristics under the mutual influence of various tunnel lengths and numerous lateral obstacles on mountainous highways. According to the driver’s need for lateral safety distance in different scenarios, the conditions and scope of the occurrence of the shy away effect are defined, and a dynamic avoidance prediction model is established in multiple scenarios. It was demonstrated that, when there were no lateral dynamic obstacles, drivers were influenced by the tunnel sidewalls to drift away from them. However, when lateral dynamic obstacles were present, drivers’ driving trajectories were corrected to be closer to the inside of the lane. The influence of vehicles of the same type resulted in the trajectory offset to the left by 0.2 m (extra-long tunnel), 0.7 m (long tunnel), 0.5 m (medium tunnel), and 0.7 m (short tunnel) compared with the driving trajectory without the influence of the obstacle. The influence of trucks causes the trajectory offset to the left compared with the driving trajectory without obstacles by 0.2 m (extra-long tunnel), 0.5 m (long tunnel), 1 m (medium tunnel), and 1.75 m (short tunnel). There is some variation in the degree of risk to the driver from different obstacles under different tunnels. The lateral distance between the driver and the dynamic obstacle is related to the nature of the available driving distance ahead. A sufficiently long driving maneuver distance enables the subject vehicle to gradually overtake the lateral dynamic obstacle in a more stable state. Dynamic avoidance models with fitting accuracies of 0.6–0.99 were implemented to predict vehicle trajectories in different tunnels and under the influence of various lateral dynamic obstacles. The study of the correlation of vehicle trajectories under the influence of various factors in tunnels is completed by the research findings, which can serve as a foundation for the design of driving behavior regulation, an improvement in traffic safety facilities, traffic management, and monitoring of lateral safety distances of intelligent vehicles in tunnels.

Experimental analysis on the progressive failure mechanism of soft rock subjected to tunnel excavation

The failure of the soft rock can seriously threaten the construction and operation of tunnels, which may suffer from larger deformation and instability. The knowledge of the failure process and mechanism of soft rock can help to optimize the tunnel design and construction. In the present paper, a large-scale physical model test with the use of both contact and non-contact measurement methods was conducted to investigate the progressive failure mechanism of soft rock. The results show that a notable pattern of progressive failure was observed in the soft rock, whereby failure initiates in the proximal regions and propagates to the distal regions within the surrounding rock. The occurrence of the failure intensifies the deformation of the soft rock, and the tunnel suffers from the cross-section flattening finally. The effectiveness of the non-contact measurement method was accessed by the comparison of the strain measurements between embedded sensors and digital photogrammetry analysis. Subsequently, the radius of the failure zone determined by the stress distribution and mechanical analysis is between two and three times the radius of the tunnel. The results of model tests were then verified by numerical analysis. Eventually, the failure modes were evaluated by local relative deformation. The shear failure takes place in the tunnel inverted arch which suffers from large shear stress, while compression failure appears on the tunnel sidewall, and the tension failure occurs at the top of the tunnel arch.

Numerical modeling of seismic performance of shallow steel tunnel

Advanced numerical models can be used to complement experimental results and further elucidate their findings. This is particularly true when certain scaled model “adjustments” are incorporated in the testing scheme to reduce the testing cost or schedule. This study conducts comprehensive finite element modeling to simulate large-scale shaking table tests conducted by Kim et al. (2023) [1] to evaluate the seismic performance of steel tunnels. The numerical model was calibrated by comparing its predictions with the experimental observations in the initial tests. The calibrated model was then validated by comparing its predictions with the results obtained from other test models and subjected to different input ground motions. The validated model was employed to comprehensively investigate the effects of the testing scheme parameters including the input motion time scaling, tunnel burial depth, and soil relative density. It was found that reducing the time scale factor during the tests led to decreased seismic responses. It was also found that the presence of overburden soil on top of the tunnel resulted in higher seismic bending moment values, and that higher overburden height increased both lateral and vertical soil pressures on the tunnel side walls and top slab. In addition, lateral soil distortion and tunnel deformations were found to be directly correlated with the overburden soil height. Furthermore, in the absence of overburden soil, there was a significant amplification in horizontal soil acceleration. The results demonstrated that lower-density sand bed experienced greater acceleration amplification and larger displacement, and the tunnel experienced larger lateral soil pressure and higher racking. Additionally, the results revealed that subjecting the same soil bed to several shaking tests affected its stiffness, and hence affected the test observations in the subsequent tests. This should be considered when planning shaking table tests. Finally, the strain values and racking ratios obtained from the numerical simulations and the shaking tests were in agreement with the values obtained from the FHWA procedure.

Tunnel excavation based on FLAC3d numerical simulation

A semi-circular arch straight wall tunnel with a span of 10m, a side wall height of 5m and a buried depth of 500m is excavated in a class IV surrounding rock. Assuming that the surrounding rock is an ideal elastoplastic material, the following problems are analyzed by using finite element or finite difference method: the arch roof subsidence and the horizontal convergence of the side wall after tunnel excavation under the action of gravity stress field and the size of the plastic zone in the surrounding rock. If the lateral pressure coefficient is 0.5-3, the effects of structural stress on the subsidence of the tunnel arch, the horizontal convergence of the side wall and the plastic zone are analyzed. If the bolt support is adopted after excavation, the system bolt shall be laid on the tunnel arch and side wall. The bolt shall be a full-length metal bolt, perpendicular to the tunnel wall, with a spacing of 1.5m, a length of 3.0m, and a diameter of 25mm. The thickness of shotcrete is 100mm, the number is C20, and the supporting effect is analyzed.

Research on concrete early shrinkage characteristics based on machine learning algorithms for multi-objective optimization

Cracking phenomena in tunnel side wall structures (TSWS) increasingly jeopardize their longevity due to water leakage, reinforcement corrosion, and eventual collapse. The primary contributor, early-age shrinkage (EAS) induced by hydration reactions, significantly undermines structural stability and durability. The integration of expansion agents (EA) and fibers presents a low-cost, efficient strategy to counteract EAS-induced cracking. Despite its promise, limited research on the influencing factors constrains its broader application. This study delves into the impacts of EA content, the CaO–MgO ratio, and fiber reinforcement on flexural strength (FS), compressive strength (CS), and EAS, revealing a complex interplay where EA and CaO content detrimentally affect mechanical properties yet beneficially influence EAS. Results showed that EA and CaO content had negative effects on the mechanical properties, but had positive effect on EAS. Additionally, Random Forest (RF) was developed with hyperparameters refined via the firefly algorithm (FA) based on the experimental data. The validity of the built RF-FA models was verified by substantial correlation coefficients and low root-mean-square errors. Subsequently, a coFA-based firefly algorithm (MOFA) was proposed to optimize tri-objectives of mechanical properties, EAS, and cost simultaneously. The Pareto fronts were obtained effectively for the optimal mixture design. This study contributes to its practical implications, offering a scientifically grounded approach to enhancing TSWS concrete design for improved performance and durability.

Spacing Analysis of Casting Dolly Windows for Tunnel Sidewall Lining Based on the Flow Characteristics of Freshly Mixed Concrete.

During the actual construction of tunnel sidewall lining, construction workers often use only one or two windows per layer for pouring in order to reduce the construction sequence, which often leads to a reduction in the quality of tunnel sidewall concrete pouring. Therefore, this study analysed the necessity of the window-by-window pouring of sidewall lining through the study of concrete flow characteristics of the tunnel sidewall lining pouring process, and the reasonable spacing of pouring windows was analysed. This study firstly verified the accuracy of the simulation parameters and the feasibility of the simulation method of the lining pouring process through indoor experiments and simulation analyses, and then it numerically simulated and analysed the flow of concrete during the lining pouring process of tunnel sidewalls. The following conclusions were made: the smaller the slump of the freshly mixed concrete, the higher the pumping flow rate; additionally, the shorter the one-time pouring distance, the smaller the spacing of the trolley feeding window should be. Furthermore, this study makes suggestions for the reasonable spacing of pouring trolleys under several working conditions.

Effect of uniaxial loading on the spalling of concrete panels for Melbourne's Metro Tunnel Project

AbstractThe Metro Tunnel is a Victorian Government funded infrastructure project which will create a new end‐to‐end rail line from Sunbury in the west to Cranbourne/Pakenham in the south east, with bigger and better trains, next generation signaling technology and five new underground stations. This article provides a detailed summary of the structural fire testing requirements for the platform tunnel side wall and arch lining in the Metro Tunnel's State Library and Town Hall stations. Contrasted to building fires, tunnel fires are more significant within a few minutes due to the confined space which can cause concrete spalling and jeopardize the bearing capacity of the tunnel, which is a significant concern to designers. The catastrophic European tunnel fire events in 1999 and 2001 led to the development of innovative regulations and recommendations, including guidelines endorsed by the European Federation of National (EFNARC 132F r3:2006) and Efectis R0695:2020. This paper explains the methodology taken to design the fire rated concrete test for the platform tunnel side wall and arch lining in the State Library and Town Hall stations of Melbourne's Metro Tunnel Project for structural stability for the period of a serious fire event. For the first time, uniaxial loading (500T) was applied to five large‐scale flat concrete panels (1800 × 1800 × 400 mm) which are normally unloaded during fire exposure and exposed to the RABT ZTV (rail) fire curve. The first testing program investigated the influence of polypropylene dosage in the concrete mix design and its effect on the magnitude and severity of concrete spalling. The results indicated that the recommended 2.0 kg/m3 polypropylene dosage requirement as specified by Eurocode is conservative. Concrete mix designs with a stable aggregate and the correct curing regime can mitigate spalling at significantly lower polypropylene dosage rates. The water pooling effect was evident during the fire testing and the surface cracking that developed was vertical to the surface, allowing for the release of the pore water pressure build‐up.

Modeling of spalling failure of in-situ rock mass for quantification of the source mechanics with flat-joint model and moment tensor

Spalling failure caused by excavation unloading in tunnels under high in situ stress is a common phenomenon. Here, we attempt to use a three-dimensional flat-joint model (FJM3D) combined with a moment tensor to simulate the process of spalling failure. FJM3D simulation showing the process of micro-crack initiation and propagation in the surrounding rock from a micro-perspective. The nature of the source mechanism is quantitatively assessed by moment tensor analysis. There are a large number of micro-cracks extending deep at the shoulder and foot of the tunnel. This model reproduces similar thin slabs and fracture orientations in Mine-by Experiment (MBE). The excavation disturbed zone (EDZ) characteristics around the MBE show that the tunnel crown and invert are dominated by tensile mechanisms, the tunnel sidewalls are dominated by implosive and shear mechanisms, and the tunnel shoulders are butterfly shaped with tensile and implosive sources. The nature of these sources are not purely tensile/shear cracks, but some isotropic/deviatoric components also play a role. The magnitude and orientation of the principal stress near the excavation face are linked to the advancement of the tunnel face and are related to the direction of micro-cracks initiation and propagation, which sheds new light on the failure mechanics of spalling failure.

Research on characteristics of thermal smoke movements of twin fires in a tunnel under reduced pressure

In this study, numerical simulations were conducted to investigate the behavior of thermal smoke movement in tunnels under reduced pressure, with the aim of providing scientific guidance for controlling smoke and heat in the event of tunnel fires. The variables examined included fire spacing (0–6 m), atmospheric pressure (55–100 kPa), and overall heat release rate (6–18 MW). The analysis revealed that the temperature method, which considers relative temperature deviations along tunnel centerlines and on tunnel sidewalls, is effective in identifying the initial position of one-dimensional smoke movement (TY=0 - TY=4.9) / TY=0 ≤ 5 %. It was found that under reduced pressure, the mass of air entrained into the smoke gas per unit time decreased, resulting in a lower mass-flow rate. Specifically, at 100 kPa, the mass-flow rate was approximately 1.4 times higher than at 55 kPa for the same simulation scenario. The effect of fire spacing on the mass-flow rate was found to be weaker compared to pressure, particularly during the non-interaction stage of the fire. The air entrainment coefficient (β) displayed a negative correlation with environmental pressure and positively correlated with fire-heat release rate. In all cases, the β value for dual fire sources in a tunnel ranged from 0.0008 to 0.0022. Finally, a segmented function was developed to forecast the mass-flow rate of thermal smoke, taking into account various factors such as fire source parameters, environmental parameters, and tunnel restrictions.

Hydrothermal characteristics of a cold regional tunnel under different climatic scenarios

Cold regional tunnels have been encountering numerous frost damages as a result of dynamic changes in hydrothermal conditions of tunnel structural layers. The climate change is recognized as a major contributor for the problems. In this study, the hydrothermal conditions of a high speed railway tunnel are evaluated under different climate scenarios based on in-situ data and numerical analysis. Subsequently, the effect of different thicknesses of insulation board on hydrothermal conditions inside the tunnel is compared and the reasonable thickness is obtained. The main findings are: The temperature and unfrozen water content gradually decreased and the ice content gradually increased with the service time of the tunnel in the early 15 years; the maximum frozen depth occurs at the tunnel sidewall and it with a depth of 1.64 m within 30 years after the construction. The hydrothermal conditions inside the tunnel are significantly affected by annu?al mean air temperature (AMAT) and annual range of air temperature (ARAT); the maximum frozen depth decreases with AMAT, but increases with ARAT. After the XPS board with a thickness of 5 cm is laid in tunnel structural layers, the temperature at the most unfavorable position is 0.55?C in the cold season, which suggests that frost damages disappeared and this method can be used to protect the tunnel against the frost damages. This paper can provide a basis for heat insulation design of the cold regional tunnels.

Deformation Mechanism and Control Measures of Large-Span Tunnels in Steep Layered Surrounding Rock

Large-span tunnels often encounter large deformation and failure when crossing layered sedimentary structures, particularly sedimentary structures that have been steeply inclined by geologic processes. This paper takes the Yongle Tunnel on the G544 line in Jiuzhaigou County, Sichuan Province, China, as an example and analyzes the deformation and failure characteristics of the tunnel through a field investigation and field test. Then, through theoretical analysis and numerical simulation, the influence of the section size, rock dip angle, and rock thickness on the deformation of the tunnel is analyzed to reveal the tunnel’s deformation mechanism. Finally, effective control measures are put forward based on the examination. The results show that the tunnel suffers from unobvious asymmetric deformation. The convergence deformation of the tunnel side wall and the sensitivity to the section size are much larger than the vault settlement and haunch convergence. The large deformation of the tunnel is caused by improper construction methods and weak structural planes. The deformation of the tunnel was significantly reduced by adapting the center diaphragm method, with anchors placed as vertically as possible to the rock or at large intersection angles and by strengthening the radial grouting of the surrounding rock. The research results can provide a reference for tunnels in similar strata.

Experimental study on out-of-plane seismic performance of precast composite sidewalls of utility tunnel with grouting-sleeve joints

The precast composite reinforced concrete wall with the advantages of fewer joints, superior impermeability and rapid construction provides an efficient and environmental friendly alternative in the construction of underground utility tunnels in the last few years. To investigate the seismic performance of precast concrete composite walls of utility tunnels with grouting-sleeve connection under out-of-plane loads, a series of quasi-static cyclic tests were performed on the full-scale sidewall specimens with different axial compression ratios in this study. The experimental results including the failure modes, crack distributions, and the influence of different connections on the out-of-plane seismic performance of precast concrete composite wall were carefully examined and compared with those from the cyclic tests of the cast-in-place sidewalls of the utility tunnel. The test results show that the seismic performance of the precast concrete composite sidewall specimen, such as the hysteresis curves, the ultimate bearing capacity, stiffness degradation pattern and the ductility ratio, is basically the same as that of the cast-in-place specimen, indicating that the seismic performance of the prefabricated structure is equivalent to that of the cast-in-place structure. Moreover, the grouting-sleeves of the joints can effectively transfer the reinforcement stress until the failure of the precast concrete composite sidewall specimens, which exhibits excellent out-of-plane ductility and serviceability.

Experimental investigation on biaxial mechanical properties of laminated rock and floor heave mechanism of tunnel based on DIC

Floor heave at the bottom of a tunnel is a common defect during tunnel service. To study the deformation behavior and failure characteristics of the floor, laminated sandstone specimens with precracked U-shaped grooves were prepared, and a series of biaxial compression tests were carried out in the laboratory. Two typical floor structures of a tunnel (with and without inverts) and four lateral stress levels (σ2 = 0, 5, 10 and 15 MPa) were considered. The effects of lateral stress and inverted structure on the deformation and failure characteristics of the floor were investigated. The displacement, strain evolution and failure extent of the floor were analyzed based on the digital image correlation (DIC) technique. The testing results show that the stress concentration at the U-shaped grooves of the specimens can be effectively reduced by the inverted structure. The specimen with an invert can bear more axial deformation and axial stress than that without an invert. The V-shaped notch failure behavior occurred near the tunnel sidewalls for the specimen without an invert, and it occurred in the middle of the tunnel floor for the specimen with an invert. The failure intensity of the V-shaped notch was positively related to the lateral stresses. With the increasing of axial stress, the heave displacement at the tunnel floor gradually increased, while the settlement displacement of the sidewall showed a trend of first increasing and then decreasing. The tensile strain concentration area of the floor undergoes a process of increasing and then decreasing and finally transforms to compressive strain. The failure characteristics of the sandstone specimen observed in the laboratory tests are consistent with the phenomena in real tunnel engineering. In addition, the deformation and failure mechanism of the tunnel floor was analyzed. The key points for the treatment of tunnel floor heave are put forward based on the testing results.

Research on landscape elements in urban tunnel sections under driving conditions

Traditional urban tunnel landscape design focuses on static conditions and neglects the influence of dynamic visual perception differences on the landscape effect that drivers experience under actual driving conditions. To optimize the design of tunnel landscapes both qualitatively and quantitatively, it is necessary to extract and analyze the landscape elements present in urban tunnel sections while considering dynamic visual perception. In the present study, a geometric visual region model was established by introducing the concept of equivalent radius based on the relationship between speed and visual changes. Three typical categories of tunnel landscape materials were collected using field surveys and video shooting methods. Geometric characteristics of landscape elements were extracted from pixelated dynamic visual images, resulting in evaluation indicators for these elements, and the element grades were determined using the Schroeder method. An analysis was conducted to identify the main landscape elements and their distinct characteristics in urban tunnels. Critical components that were examined included tunnel ceilings, sidewalls, road surfaces, and pedestrian walkway object marking. The distribution of these elements in terms of pixel area ratios was determined to be 29.7% for tunnel ceilings, 27.2% for sidewalls, 19.6% for road surfaces, and 4.9% for pedestrian walkway object marking. Optimizing these designs requires controlling unity and contrast in colour design as well as hierarchy, rhythm, proportionality, and unity in pattern design. The results from the field investigation, pixel extraction, and correlation coefficient analysis provide strong evidence supporting the correlation between the main landscape elements identified by the theoretical model. In fact, the correlation exceeds 50%, indicating a significant relationship between these elements. These findings validate the reasonableness of the theoretical model in achieving quantitative design for significant landscape areas and provide a solid foundation for establishing an evaluation index system for urban tunnel landscapes.

Impact of urban tunnel sidewall effect on drivers: Examining visual characteristics and driving behavior across different lanes

Urban tunnels have been widely used as special transportation infrastructure. This study investigated the impact of the urban tunnel sidewall effect on drivers, focusing on the drivers’ visual characteristics and driving behavior as the primary research objectives. In this study, numerous real vehicle tests were conducted in the middle section of an urban tunnel, focusing on different lanes. The drivers’ visual characteristics were examined through the distribution of gaze points and fixation duration, and driving behavior was assessed using the vehicles’ lateral offset and acceleration. The drivers’ visual characteristics and driving behavior were analysed together to investigate the impact of the sidewall effect on the relationship between the visual information input and driving behavior output. A questionnaire was administered after the experiment to assess the subjective experiences of each participant. The results indicated significant variations in the impact of the sidewall effect on driver attention distribution and vehicle stability across different lanes. Drivers in the left lane were the most affected and had the highest driving risk, followed by those in the right lane; those in the middle lane had the least driving risk. Meanwhile, when drivers in the left or right lanes focus their gaze on the adjacent sidewall or shortly afterwards, the vehicle experiences a higher lateral acceleration away from the sidewall compared to other areas.

Excavation and Construction Technology of Diversion Tunnel under Complex Geological Conditions

During the construction of a diversion tunnel, geological problems often include faults, fragile strata, hard rock formations, karst landforms, etc., which may have adverse effects on the excavation and construction of the diversion tunnel. Based on the analysis of the engineering overview, this study designed a new construction technology for the excavation of water diversion tunnels in hard rock layers and high-karst areas. Based on tunnel seismic prediction (TSP) technology to achieve advanced geological prediction, combined with actual geological conditions, construction difficulties are analyzed. Then, detection technology is used to collect two-way travel time, amplitude, and waveform data. By processing and analyzing the detection image, the spatial orientation and length of the main tunnel during the construction of the diversion tunnel are calculated. After completing the construction ventilation and wind, water, and electricity layout, the excavation construction procedure is designed. In the specific excavation design, the tunnel curtain excavation technology, tunnel body excavation and support technology, excavation grouting technology, important unfavorable geological tunnel section excavation technology, upper/lower flat section excavation technology, upper/lower curved section excavation technology, and vertical shaft section excavation technology were elaborated. Finally, a plan was made for the reuse process of slag material and a construction quality control system was established. During the testing process, it was found that the antidamage coefficient of the side wall was above 0.9 after using the technology described in this article. Therefore, it indicates that the excavation construction technology designed in this article can ensure the support capacity of the side wall of the diversion tunnel, which is suitable for the excavation of the main tunnel during the construction of the diversion tunnel.

Appraisal of a galvanic-source transient electromagnetic method for hazardous water structures beyond tunnel sidewall

Appraisal of a galvanic-source transient electromagnetic method for hazardous water structures beyond tunnel sidewall