Mountain Tunnel Research Articles

Safety Assessment of Exit Advance Guide Signs in Mountainous Highway Tunnel Based on Eye-Tracking Technology

Exit Advance Guide Signs play an important role in driving safety on highway tunnels. With the increase of mountain highway in recent 10 years, how to set exit advance guide signs inside the mountain highway tunnels become a new problem in China. This paper evaluates the effects of setting schemes of Exit Advance Guide Signs in mountain tunnels through simulation experiments. Specially, exit advance guide signs in the mountainous highway tunnel were divided into location sign and distance sign. Six schemes of different height, width and spacing were tested, in which the distance sign was on the left or right wall of the tunnel, and the vehicle was on the left lane. A Markov chain was used to analyze the driver's eye movement characteristics to evaluate the effect of separate guide signs. The results were as follows: if the distance sign was set on the left wall, the scheme 4 where height, width and spacing of 1.5m was the best choice, because the change rate of the driver's pupil area was higher than the threshold, attention to distance signs increased to 10.42%, and dashboard gaze also increased. These characteristics show that the traffic sign setting effect was obvious, and didn't affect the driver's driving safety; if the distance sign was set on the right wall, the scheme 6 where height, width and spacing of 2m was the best choice, because drivers pay the highest attention to area 5 and it did not exceed 60%, Meanwhile, the driver's fixation distribution of scheme 6 was the most stable. This study can optimize exit advance guide signs setting in the mountainous highway tunnel, then contributing to reduced traffic accidents and making mountain highway transport more sustainable.

Dynamic Response of the Entrance Structure of an Elliptical Mountain Tunnel under the Action of SH Waves

Generally, the surrounding rock at the entrance of a mountain tunnel is loose, and the entrance has more slopes due to topography, which causes the tunnel entrance section to be easily destroyed under an earthquake. Based on the established slope model with a single free surface, this paper adopted the elastic wave theory to derive the analytical solution of the strain at the entrance of the mountain tunnel when the SH wave is incident perpendicularly to the bottom of the tunnel; besides, the factors affecting strain were also analyzed. The tangential strain curve at each point of the entrance section takes the centre of the elliptical tunnel as the centre of symmetry, forming symmetry between the left and right sides and mirror symmetry between the top and bottom sides. Then, large‐scale shaking table model experiments were conducted to model the actual working conditions, and the correctness of the analytical solution was verified. The research can provide a theoretical reference for the seismic design of the entrance section of the high‐speed railway tunnel and greatly improve the understanding of its seismic response.

Rapid Assessment and Classification for Seismic Damage of Mountain Tunnel Based on Concentric Circle Method

Concentric circle method (CCM), a new method based on analytic hierarchy process (AHP) and numerical discretization of 40 mountain tunnels damaged by Wenchuan earthquake in China, is proposed to rapidly assess the seismic damage level (SDL) of mountain tunnels. The new method consists of four components. First, according to the type and degree of seismic damage of tunnel, the whole tunnel is divided into a number of successive sections. Second, four factors (i.e., slope and portal damage, lining damage, pavement damage, and earthquake collapse) are selected as the main controlling factor set, and then multilevel factor sets are proposed to establish the assessment system. Third, the discretized assessment indexes and classification criteria are established for the rapid assessment of SDL of mountain tunnel. Finally, based on the comprehensive analysis on the SDL of each section, the SDL of the whole tunnel is calculated in terms of the seismic damage index and synthetic radius. With the assessment results shown on a straightforward concentric circle diagram, the proposed CCM method can rapidly and reliably assess the SDL of mountain tunnel to win over precious time for emergency rescue and provide references for the repair of damaged tunnel. In addition, the accuracy and applicability of the proposed method is verified by using a case study of Longxi tunnel located at the epicenter of the Wenchuan earthquake in China.

A Novel Safety Evaluation Method for Mountain Tunnel Surrounding Rock Based on Vague Set

A Novel Safety Evaluation Method for Mountain Tunnel Surrounding Rock Based on Vague Set

Study on Stability of Surrounding Rock of Mechanized Construction in Tunnel Entrance Section

With the development of tunnel construction technology and mechanical equipment, the mechanized drilling and blasting construction of mountain tunnels has gradually developed, but there are still certain problems in the mechanized tunnel entry. Relying on a tunnel project in Yunnan, this article uses FLAC3D software to study the stability of surrounding rock under the condition of mechanized large-section construction of shallow buried section of the tunnel entrance. When the shallow buried section of the cave entrance is constructed by the micro-step method, the surrounding rock displacement and plastic zone changes of the surrounding rock before and after the use of different cyclic footage and the tunnel face reinforcement when the tunnel face is used are compared and analyzed. The results of the study show that when the tunnel face is not reinforced, in order to ensure the safety of construction, the mechanized excavation cycle footage of the tunnel entrance section should be controlled within 1.2m, and the overlap length of the leading pipe shed should be greater than 5m; if the circulation is to be increased for footage, the tunnel face must be reinforced. Under the condition that the tunnel face is reinforced with glass fiber anchors with a length of 10m and a pitch of 1.5m, the cycle footage can be increased to 1.8m at most.

Influence of front slope gradient and the angle between tunnel and slope on stability of tunnel portal

Shallow buried and unsymmetrically loaded tunnel is the most common type of mountain tunnel portal. Currently, most of the studies mainly focus on the stability of side slope, while the investigation on the deformation of the front slope after tunnel excavation is relatively less. In this paper, the influence of front slope gradient and the angle between tunnel and slope on stability of tunnel portal was analyzed by FLAC3D. The results show that: When the front slope angle is greater than 40°, the slope deformation caused by tunnel excavation is larger with the increase of slope angle. In order to ensure the safety of construction, we should not only pay attention to the treatment of the front slope before the tunnel excavation, but also pay attention to the monitoring of the front slope deformation during the excavation of the tunnel portal section. And the most suitable entry angle between tunnel axis and the front slope is 0°, which can control the vertical displacement of relatively large deformation. The research conclusions can provide some reference for the excavation and support design of mountain tunnel portal.

Gotthard Base Tunnel : World's Longest Railway Mountain Tunnel

Switzerland was suffering from serious traffic problem and so it proposed a gigantic project. Over 35 miles long tunnel would cut through the heart of the Swiss Alps. Redirecting the rush and traffic of Europe not over the Alps but under the Alps. To do this, miners had to punch their way through the hardest rock on this planet. For this a TBM was required, each 3 stories high and larger than 4 football fields, working continuously for 6 years. This project was very dangerous and outrageously expensive at a price tag of $10 billion.

Single-channel blowing-in longitudinal ventilation method and its application in the road tunnel

The longitudinal ventilation method is widely used in extra-long tunnels because of its simple ventilation mode and lower construction and operation costs. This paper originally proposes a new longitudinal ventilation method, the single-channel blowing-in longitudinal method. Only one ventilation channel is set between uphill line and downhill line of main tunnel, and relatively fresh air near the entrance of the downhill line is sent to the section close to the uphill line exit through the ventilation channel. The authors deduced the ventilation theory, design method and applicable conditions in detail, analyzing six cases to reveal the variation regulation of optimal location of single-channel xfit, one-year ventilation energy consumption Pone, total ventilation energy consumption Ptotal, and applicable scope of the tunnel length Lmax. The results suggest the following. (1) The optimal location of single-channel xfit enable the total ventilation energy consumption in serving period Ptotal to be the minimal, but usually it cannot let one-year energy consumption Pone reach the minimum. (2) The single-channel system makes full use of the surplus fresh air and the piston effect of traffic wind in the tunnel, showing a better energy-efficient property from a long-term perspective (3) For the whole serving period, xfit and Ptotal is relatively fixed when the traffic volume changes linearly. Meanwhile, this method has been successfully applied to China Mingtang Mountain Tunnel, and the relevant engineering application experience would be helpful for the similar projects.

Three-dimensional seismic performance of mountain tunnel with imperfect interface considering P wave

A semi-analytic solution based on three-dimensional elastodynamic was developed to investigate the longitudinal deformation of deep-buried tunnels subjected to compression P wave. The wave function expansion method and the complex function were applied to express wave fields in different regions. An elastic spring model was introduced to satisfy the imperfect interface boundary between the tunnel lining and its surrounding rock mass. Influences of wave propagation direction and imperfect interface were discussed to illustrate the seismic performance of the mountain tunnel. Numerical results showed that both the wave incidence angle and imperfect interface influenced greatly the magnitude and distribution of dynamic stress. Besides, some fundamental deformation and failure modes were obtained from the numerical analysis considering the incidence angle. Based on the modes, the longitudinal deformation and damages of tunnel subjected to the 2016 Kumamoto earthquake were analyzed.

Application of PS-INSAR Technique on Health Diagnosis of the Deformable Body on Front Slope beside Mountain Tunnel Portal

When tunnel construction develops to surrounding mountainous areas, tunnel portal presents the topographic characteristics of “high, steep, and slant” and geological characteristics of kinds of hugely thick colluvial or residual slope, and the health condition of the deformable body on front slope beside tunnel portal has a great influence on tunnel construction and operation. Tunnel portal has suffered from many disasters, and it is urgent to study and solve the engineering problem on how to diagnose the health condition of front slope beside tunnel portal quickly and accurately. Based on the tunnel of Jianquan village, this paper uses PS-INSAR technique for the first time to analyze and diagnose the health condition of the deformable body on front slope beside mountain tunnel portal at the construction stage and operation stage, so as to provide early warnings to unstable deformable body at tunnel portal and provide strong bases for the treatment of unstable deformable body. Therefore, PS-INSAR technique promotes the health monitoring method for deformable body on front slope beside mountain tunnel portal to a higher level.

Unascertained Measure-Set Pair Analysis Model of Collapse Risk Evaluation in Mountain Tunnels and Its Engineering Application

Collapse is a major geological disaster that occurs during mountain tunnel construction. However, the accuracy of collapse risk assessment is generally restricted by evaluation factors or methods. This paper proposes a novel integrated collapse risk evaluation method for mountain tunnels based on case-based reasoning, rough set theory, and unascertained measure-set pair analysis (UM-SPA) theory. First, the risk surroundings and risk factors involved in tunnel collapse are summarized by the analytic hierarchy process, and a preliminary risk evaluation index system is established. Then, an attribute reduction algorithm based on the conditional information entropy of a rough set is proposed and applied to cases with similar attribute characteristics as those of the tunnel to be evaluated, to remove the relatively insignificant or redundant indices and improve the reliability of risk assessment. Finally, taking the relationship between tunnel collapse and its evaluation indices as an unascertained system, Set Pair Analysis (SPA) theory is introduced to optimize the credible degree recognition criteria of unascertained measure theory (UMT). Combined with the modified entropy weight method, a UM-SPA model for tunnel collapse risk evaluation is established to calculate the level of collapse risk quantitatively and predict the development trend of risk dynamically. Taking Xiucun Tunnel passing through fault F18 as an example, collapse risk is evaluated and compared with the evaluation results of traditional UMT and field status. The results demonstrate the feasibility and efficiency of the proposed approach and provide a new idea for collapse risk prediction while constructing mountain tunnels.

Grouting Treatment of Water and Mud Inrush in Fully Weathered Granite Tunnel: A Case Study

When mountain tunnel passes through completely weathered granite strata, water and mud inrush is easy to occur, causing casualties and economic losses. Grouting is a common and effective treatment method for water and mud inrush disaster. The current existing researches focus on theoretical analysis, numerical simulation, and laboratory test, and the researches based on the field of engineering application are few. Based on the fully weathered granite tunnel of Junchang tunnel in Guangxi, this paper studies the grouting treatment of water and mud disaster in the fully weathered granite tunnel. This paper first introduces the geological and hydrological conditions of Junchang tunnel in order to understand the causes of water inrush and mud inrush. Then, the treatment method of full-section curtain grouting is introduced. During the grouting, the combination of exploration and injection is adopted. According to different hydrological conditions, different kinds of grouting materials are adopted. After grouting is completed, Transient Electromagnetic Methods, water inflow analysis, borehole investigation, and P-Q-T method are used to evaluate the grouting effect. According to the reaction of the detection results, the weak part of grouting can be supplemented to improve the grouting quality. The results show that the curtain grouting is effective for the treatment of water-mud inrush disaster in the fully weathered granite tunnel. This study provides a reference for the treatment of water and mud inrush in other similar tunnels.

Distribution Law of Water Pressure on the Lining in Tunnels with Water Blocking and Drainage Control Design

For mountain tunnels in water-rich areas, the water pressure on the lining (WPOL) has a significant impact on the parameter selection and operation safety of the lining. Based on the theory of groundwater dynamics and complex function, this paper derives the analytical expressions of the WPOL and the seepage pressure outside the grouting ring. Under different supporting conditions, the authors analyzed how the WPOL was influenced by the head of groundwater, the permeability of the surrounding rock, and the permeability of the grouting ring. The results show that the permeability of the secondary lining not only affects the drainage capacity of the drainage system, but also greatly impacts the WPOL on the composite lining; the WPOL decreases linearly with the growing drainage capacity. To control the WPOL on the composite lining, designers of mountain tunnels in water-rich areas should carefully plan the water blocking and drainage control in accordance with the surrounding environment.

Risk assessment of collapse in mountain tunnels and software development

As most frequent geological hazard, the collapse is a great threat to safe construction of tunnels. The risk assessment method for collapse in mountain tunnels was presented with six evaluation indices, including surrounding rock level I1, rock mass integrity I2, buried depth I3, bias angle I4, groundwater I5, and construction factors I6. According to the non-linear relationship between the collapse and its influencing factors, the synthetic attribute assessment model was improved based on the concept of normal distribution. The weight of each index consisted of two parts: the subjective weight obtained by analytic hierarchy process (AHP) and the objective weight determined by correlation analysis. The Mountain Tunnel Collapse Risk Assessment System (TCAS) was developed based on Visual Studio 2012 and C# programming language. The TCAS was applied to assess the collapse risk of Hongyansi tunnel from Baoyi to Yichang expressway (Xiangyang section). The result was a good agreement with actual excavation situation that a “closed door” collapse happened. Therefore, the software system can not only accurately assess the risk level of collapse but also will play an important role in rapid assessment in the whole process of tunnel construction.

Influence of Ground Water on Blasting Construction of Adjacent Tunnel

During the construction of a mountain tunnel, water-rich strata are often encountered. Current research on the influence of groundwater on the blasting construction of the adjacent tunnel is not in-depth enough. Based on the Yingpanshan tunnel project of Huali Expressway in Yunnan Province, China, this paper analyzes multi-factor couplings such as blasting dynamic load, large-section excavation, groundwater and adjacent construction. An adjacent construction model with a size of 80×80×50m is established by COMSOL Multiphysics software. Considering the change of permeability and elastic modulus of the model, the influence of blasting construction on the adjacent construction is reflected by the vibration velocity of the existing tunnel lining. The results show that the impact of groundwater on the safety of the adjacent structure is mainly related to the permeability, and its influence degree increases with the water pressure. In the water-rich stratum with high permeability of rock mass, it is necessary to pay attention to the influence of groundwater on the safety of adjacent blasting construction.

Construction Technology of Comprehensive Disposal for Shallowburied Section of Mountaintunnel

In this paper, the Wushi tunnel of Qingyun Expressway in Guangdong Province is taken as the engineering background, the shallow buried section of mountain tunnel is the area with frequent tunnel diseases, in order to solve the problems of poor self-stability of the excavation surface, destruction of supporting structure and water inrush caused by fully weathered surrounding rock in shallow tunnel, after integrating the treatment technology of the existing fully weathered surrounding rock shallow buried tunnel, pre-reinforcement treatment of fully weathered granite with cover grouting technology on deep surface, the working face is excavated after being pre-supported by a double-layer advanced small pipe and using a new type of self-adhesive waterproof membrane to ensure the waterproof effect of the lining, safe and efficient completion of shallow tunnel excavation, Then backfill the soil of the construction surface to carry out ecological restoration work. Through the study of this process, the construction process flow of the fully weathered surrounding rock shallow buried tunnel is summarized, and the key points of each construction stage are pointed out to ensure the construction quality and optimize the construction technology of the shallow buried section of the mountain tunnel, which provide a reference for other similar engineering problems.

Factors affecting the deformation of the surrounding rock of tunnel based on rough set theory

The deformation of surrounding rock is a common hazard in tunnel engineering, and it can negatively affect the quality and safety of a project. Therefore, the analysis of factors affecting the deformation of tunnels surrounding rock has essential engineering significance. This work selected two subjective factors affecting the deformation of the surrounding rock of a tunnel, namely, the excavation method and the excavation footage, and four objective factors (i.e., the tunnel burial depth, the degree of weathering, the groundwater conditions, and the uniaxial compressive strength of rocks) as the factors affecting the deformation of tunnel surrounding rock. Data on the factors influencing deformation of 25 typical deformation sections of the Tianqiao Mountain Tunnel under construction were collected to establish the condition attributes in the decision table. The actual deformation level was used as the decision attribute in the decision table. Rough set theory was used to perform a completely objective analysis of these six factors. Results of the analysis show that the groundwater conditions are the most influential factor in surrounding rock deformation with a weight of 0.3333, and the degree of weathering is a redundant factor. This study can be used as a guide for reducing or avoiding the deformation of the surrounding rock of a tunnel.

A Review on Seismic Response and Aseismic Measures of Fault-crossing Tunnels

Several earthquakes have challenged the traditional view that the seismic performance of tunnels is excellent. The seismic damage of these tunnels has led scholars and engineers to study the seismic response of tunnels and underground facilities. Many earthquake damage investigations of mountain tunnels reveal that fault or fracture zone is one of the most critical factors leading to tunnel damage. In this paper, the mechanisms of seismic damages and the main factors that influencing the seismic response of fault-crossing tunnels have been explained. Based on two different aseismic philosophies, different aseismic measures of fault-crossing tunnels including buffer layer, fiber concrete, flexible joint, grouting and enlarging tunnel across have been review, and the advantages and disadvantages of different aseismic measures as well as their application scope have been assessed. The ideal aseismic design of fault-crossing tunnels is as follows: verify the fault activity, accurately estimate the possible displacement and the earthquake intensity of the fault area, and then combine the advantages of different aseismic measures, set up composite aseismic measures at the place where the tunnel crosses the fault zone. It is believed that the present study will help in a better understanding of the seismic response of fault-crossing tunnels and have some guidance of aseismic design of fault-crossing tunnels in engineering practice.

Transversely isotropic creep behavior of phyllite and its influence on the long-term safety of the secondary lining of tunnels

Phyllite, which is a low-grade metamorphic rock with well-developed foliations, is encountered frequently during the construction of tunnels in western China. First, uniaxial compressive creep tests were performed to study the time-dependent behavior of phyllite specimens from Zhegu mountain tunnel. Then, a numerical approach was put forward based on the particle discrete element method to describe the typical creep behavior of phyllite, including its decay, steady, accelerated creep stages, and its transverse isotropy. Finally, the numerical model was adopted to investigate the failure process of secondary tunnel lining in the phyllite stratum. The following results were obtained: Ai et al. (2014) (1) The creep behavior of phyllite was affected significantly by the weak plane-loading angles and water content. Its creep strength decreased as the water content increased, and the maximum and minimum values occurred at θ = 90° and 30°, respectively; Carrillo et al. (2016) (2) The fractal dimension of fracture surface for θ = 0° was the smallest due to the shear and tensile failure along foliations. For each angle, fractal dimension increased with the increase of water content; Chen et al. (2018) (3) Micro-cracks were initiated at the initial loading stage and propagated during the entire loading process at θ = 0°, while they appeared at a higher stress level after specimens had accumulated sufficient energy at θ = 30° or 90°; Chen et al. (2019) (4) The evolution of micro-cracks was affected jointly by the inclination angle of foliations and the geo-stress field, and the cluster of cracks shows evidently asymmetric features. The results revealed the transversely isotropic creep behavior of phyllite and proposed a method which can aid more accurate predictions for design and construction with respect to geotechnical engineering structures related to layered rock mass.

Structural damage assessment of mountain tunnels in fault fracture zone subjected to multiple strike-slip fault movement

Fault fracture zones are adverse geological conditions often encountered in the constructions of mountain tunnels. Extensive structural damage to the mountain tunnels in adjacent to the fault fracture zones has been documented in the past earthquakes. In current work, three-dimensional numerical model of a water conveyance tunnel crossing multiple active strike-slip faults was established to assess the structural damage with consideration of four primary influence factors: the magnitude of fault movement, the distance between adjacent fault planes, the tunnel-fault intersection angle and the mechanical properties of the rock mass in the fault fracture zone. Two quantitative damage indices, namely, the overall structural damage index and the concrete lining crack width, are proposed in this study to investigate the structural integraty and the serviceability of the water conveyance tunnel subjected to fault movements. The numerical results indicate that the cross-sectional damage of the tunnels primarily concentrated in the vicinities of the fault planes, and the boundaries between the fault and the competent rock. With the increase of the distance between adjacent fault planes, the structural damage of the tunnel in the region near the center of the fault fracture zone rapidly decreases. The tunnel-fault intersection angle also significantly affects the performance of the tunnel under fault movement. Moreover, the increase of surrounding rock mass stiffness in the fault fracture zone reduces the extension but increases the severity of damage to the tunnel lining. Overall, the numerical results of this study provide a better understanding of the response of mountain tunnels under multiple strike-slip fault movement.