Tunnel Surface Research Articles

Visual change detection on tunnel linings

We describe an automated system for detecting, localising, clustering and ranking visual changes on tunnel surfaces. The system is designed to provide assistance to expert human inspectors carrying out structural health monitoring and maintenance on ageing tunnel networks. A three-dimensional tunnel surface model is first recovered from a set of reference images using Structure from Motion techniques. New images are localised accurately within the model and changes are detected versus the reference images and model geometry. We formulate the problem of detecting changes probabilistically and evaluate the use of different feature maps and a novel geometric prior to achieve invariance to noise and nuisance sources such as parallax and lighting changes. A clustering and ranking method is proposed which efficiently presents detected changes and further improves the inspection efficiency. System performance is assessed on a real data set collected using a low-cost prototype capture device and labelled with ground truth. Results demonstrate that our system is a step towards higher frequency visual inspection at a reduced cost.

Sight distance and horizontal curve aspects in the design of road tunnels vs. highways

The design of road tunnels is an essential component in highway geometric design.The study implements reasonable criteria for obtaining the sight distance requirements of road tunnels vs. open roadways based on research overview of driving behavior, longitudinal friction characteristics, and highway safety considerations in road tunnels. These criteria assist to generate design values of horizontal curve radii for a certain range of design speeds. The assessment of stopping sight distance for road tunnel is performed by assuming: (1) a lower perception reaction time of the driver due to drivers’ vigilance along the bounded cross section, and (2) higher values of friction coefficient depending on the tunnel surface conditions: moist or dry tunnel. The stopping sight distance (SSD) design values were also generated for the “end of tunnel” (EOT) zone assuming wet pavement for desirable design. The implementation of unique criteria for stopping sight distance in road tunnels reduced significantly its design values.The analysis of horizontal curve radii in road tunnels is based on two concepts: (1) equilibrium i.e. balancing the centrifugal force by the superelevation and the radial friction factor adjusted to road tunnels; (2) conforming stopping sight distance requirement by analyzing three alternatives of the driver position along the inside lane (centerline of inside line, left hand curve, and right hand curve).It is concluded that the critical concept for safe horizontal curve radii in road tunnels (as in open roadways) is the stopping sight distance. The analysis has shown that only for the lowest design speeds (i.e. 50 and 60km/h), the equilibrium requirement generated higher horizontal curve radii. The driver position (left hand or right hand curve) has a considerable impact on the design values of horizontal curve radii. The horizontal curve radii analyzed for road tunnels are considerably lower than the open roadways’ radii. The difference increases as the design speed increases. The tunnel pavement status (especially dry tunnels) and driver behavior characteristics have therefore a substantial impact on the stopping sight distance and on the horizontal curve radii. The results are useful to provide traffic safety if the design vehicle (passenger car) speed is maintained by appropriate traffic management and enforcement.

Automatic crack detection and classification method for subway tunnel safety monitoring.

Cracks are an important indicator reflecting the safety status of infrastructures. This paper presents an automatic crack detection and classification methodology for subway tunnel safety monitoring. With the application of high-speed complementary metal-oxide-semiconductor (CMOS) industrial cameras, the tunnel surface can be captured and stored in digital images. In a next step, the local dark regions with potential crack defects are segmented from the original gray-scale images by utilizing morphological image processing techniques and thresholding operations. In the feature extraction process, we present a distance histogram based shape descriptor that effectively describes the spatial shape difference between cracks and other irrelevant objects. Along with other features, the classification results successfully remove over 90% misidentified objects. Also, compared with the original gray-scale images, over 90% of the crack length is preserved in the last output binary images. The proposed approach was tested on the safety monitoring for Beijing Subway Line 1. The experimental results revealed the rules of parameter settings and also proved that the proposed approach is effective and efficient for automatic crack detection and classification.

The Usability of Terrestrial 3D Laser Scanning Technology for Tunnel Clearance Analysis Application

After building underground constructions, spatial parameters monitoring is essential due to safety and statuary reasons. Therefore after completion of work in tunnels often supervision projects follow which include cross sections measurements, as well as ground and secondary wall layer deformations monitoring during consolidation era. Conventional approaches to achieve this type of documentations are different, however their downside is often that they are time consuming and even with combination of independent contractors, collected data is often deficient and corrupted with rough interpolations. Terrestrial 3D laser scanning (TLS) represents alternative approach to conventional monitoring methods [1]. With engineer planning approach, field work and data interpretation, TLS technology allows systematical and fast acquisition of shape and spatial orientation of complex objects and all their components. In case of shorter railway tunnels (up to 360 m) data for clearance analysis in correlation of standard cargo and tunnel surface, was captured with terrestrial 3D laser scanning method. Control of tunnel clearance is usually performed analogously and on conventional low equidistant cross section survey method. Considering that in this article we deal with relative old tunnels, in which there is no constant transversal profile but huge amount of geometric anomalies, simulation verification could be performed only with hi-grid definition survey method. With TLS larger amount of tunnels were measured and clearance analysis simulations for real case of standard cargo profile was made, based on radius and railway inclination of the tunnel. Standard or non-standard cargo transport planning with computer simulation now can be done in relatively short time. In this article is presented integration of TLS in case study of short railway tunnels with focus on clearance analysis applications with interactive and user friendly visualization for data interpretation. Other methods for different spatial parameters interpretations in underground constructions are presented as well.

Blast-induced dynamic rock fracture in the surfaces of tunnels

Hanging roofs or high hang-ups, a common problem in sublevel caving mining, usually result in a large ore loss and undermine mining safety. This paper analyzed the formation of a hanging roof and showed that increased confining pressure and reduced free surface were its main characteristics. In order to break down a hanging roof, a new method based on shock wave collision and stress superposition was developed. In this method, two blastholes containing multi-primer at different positions are simultaneously initiated at first. By doing this, a new free surface and a swell room can be created. After these holes are fired, a long delay time is given to the next blasthole so that the fragments from the first two-hole blasting have enough time to fall down. This new method was applied to three hanging roofs in one production area, and all of them were successfully broken down. Field inspection indicated that almost no damage was caused in the nearby drifts/tunnels due to the new method. In addition, the far field vibrations were found to be smaller than the maximum vibrations induced by some other blasts.

Edge bands and vertical transport in topological insulator/magnetic insulator heterostructures

The low-energy band-structure of electrons propagating on a lateral surface of a heterostructure consisting of three dimensional topological insulator (TI) and magnetic insulator layers has been calculated. The energy spectrum is highly tunable depending on the relation between the interlayer tunneling amplitude, Zeeman energy and surface potential. A ratio between the first two parameters controls a topological transition between chiral and helical surface state band-structures. In the former case localized states, whose wave-functions are confined near single TI layers, emerge in a narrow parameter range where they coexist with itinerant states. In regular superlattices these localized states form a flat band in the vertical direction. Such a localization has a topological origin. It is associated with a specific spatial spin texture of these states. The localized states vanish upon the topological phase transition from the anomalous quantum Hall regime to a trivial phase characterized by an anisotropic Dirac cone on the lateral surface of the heterostructure.

Variations in Ground Surface Responses Under Different Seismic Input Motions Due the Presence of a Tunnel

This paper examines the interaction between urban tunnel and ground surface during the different input motions. The Niyayesh–Sadr tunnel in North of Tehran with a 14m span and its environmental conditions were used as a case study. Analysis is performed using a finite difference model which takes into consideration the presence of the tunnel during the seismic motion. The soil behaviour is assumed to behave according to the Mohr-Coulomb model, and hysteretic damping is included in the dynamic analyses. Previous studies showed high amplification of displacement in the vicinity of the tunnel. This paper comprises three parts wherein the effects of the presence of a tunnel on surface accelerations, which are the basic input data used in the design of buildings, are investigated. The first part illustrates the numerical method with the related verifications. In the second part, two parameters of acceleration amplification factor and acceleration interaction factor are described. These parameters are calculated during several Ricker wavelets with different predominant frequencies and selected earthquakes with various frequency contents. The last part examines the variation of the shear strains near the surface and the residual strains. Results show that the presence of tunnel can increase the surface acceleration up to 37 % in critical cases. The distance between 0.5D to 1.0D from the centre of the tunnel on the surface is mostly affected by considering the interaction so that in the present case study, most of the buildings are placed in this critical zone.

Development of an elliptical fitting algorithm to improve change detection capabilities with applications for deformation monitoring in circular tunnels and shafts

Terrestrial laser scanning, also known as Light Detection and Ranging (LiDAR) is an emerging technology that has many proven uses in the geotechnical engineering community including rockmass characterization, discontinuity measurement and landslide monitoring. One of the newer applications of LiDAR scanning is deformation monitoring and change detection. In tunnels, deformation is traditionally measured using a series of five or more control points installed around the diameter of the tunnel with measurements recorded at regular time intervals. LiDAR provides the ability to obtain a more complete characterization of the tunnel surface, allowing for determination of the mechanism and magnitude of tunnel deformation, as the entire surface of the tunnel is being modeled rather than a fixed set of points. This paper discusses terrestrial LiDAR scanning for deformation mapping of a surface and for cross-sectional closure measurements within an active tunnel using an elliptical fit to data for profile analysis. The methods were found to be accurate to within a few millimeters when measuring 58mm of diametric difference over an 18.3m diameter circular profile, even when some sections of the data were removed from the analysis.

Numerical study on tunnel damage subject to blast-induced shock wave in jointed rock masses

In this study, numerical modeling on the damage of existing circular tunnel subject to blast-induced shock wave was carried out with DEM-based code UDEC. The disturbed zones including failure zones, open zones and shear zones around circular tunnel and peak particle velocities (PPVs) at tunnel surface are employed to analyze the damage of tunnel. The effects of joint spatial and mechanical properties, initial stress of rock mass, and magnitude of shock wave amplitude to damage of tunnel were evaluated in this study. The difference of damage between non-supported circular tunnel and bolt-supported circular tunnel subject to the same blast-induced shock wave was also studied. It is found that the orientations of joints in rock mass around the tunnel have great effects on tunnel damage. The initial stress around tunnel has relatively small influence on tunnel damage. The bolt support could greatly increase the stability of tunnel by changing the vibration form of particle velocity rather than the decreasing of PPV.

Observation of quantum-tunnelling-modulated spin texture in ultrathin topological insulator Bi2Se3 films.

Understanding the spin-texture behaviour of boundary modes in ultrathin topological insulator films is critically essential for the design and fabrication of functional nanodevices. Here, by using spin-resolved photoemission spectroscopy with p-polarized light in topological insulator Bi2Se3 thin films, we report tunnelling-dependent evolution of spin configuration in topological insulator thin films across the metal-to-insulator transition. We report a systematic binding energy- and wavevector-dependent spin polarization for the topological surface electrons in the ultrathin gapped-Dirac-cone limit. The polarization decreases significantly with enhanced tunnelling realized systematically in thin insulating films, whereas magnitude of the polarization saturates to the bulk limit faster at larger wavevectors in thicker metallic films. We present a theoretical model that captures this delicate relationship between quantum tunnelling and Fermi surface spin polarization. Our high-resolution spin-based spectroscopic results suggest that the polarization current can be tuned to zero in thin insulating films forming the basis for a future spin-switch nanodevice.

A simplified model to study the behavior of pre-tensioned fully grouted bolts around tunnels and to analyze the more important influencing parameters

This paper develops an analytical method to obtain distribution of the axial force in the pretensioned fully grouted rockbolts around a circular tunnel. For his purpose, the axial force along the bolt is calculated by the assumption of rigid connection between the bolt and rock mass. To include the effect of relative shear displacement, the condition of end boundaries of bolt is focused on i.e. the reduction of the force on the bolt head is calculated through modeling of the flexibilities of its component (washer, plate …) and tunnel surface. Then, this force is simulated by applying a fictitious compressive force on the bolt head. The distribution of this fictitious force along the bolt is obtained to subtract from that of rigid connection. According to a case study, the theoretical prediction of axial force in the passive cases is comparable to the in-situ measured data. The magnitude of pre-tensioning force, delay in installing of bolts, stiffness of bolt head, and rockbolt density are considered as parameters to perform the sensitive analysis.

Heat Transfer Enhancement of Impinging Row Jets in Cross-Flow with Mounting Baffles on Surface

The aim of this research is to enhance heat transfer on a surface of row of impinging jets in cross-flow by mounting some baffles on the surface. A row of 4 jets with inline arrangement discharging from round orifices impinged normally on inner surface of wind tunnel with simulated cross-flow. The orifice diameter (D) was 13.2 mm. The jet-to-surface distance and jet-to-jet distance were fixed at H=2D and S=3D, respectively. Four couples of baffles with V-shaped arrangement at attack angle, θ=30o, were mounted on surface in upstream or downstream of impinging jets and the location of baffles attachment is L=1.5D apart from the jet impingement region. The velocity ratios (Jet velocity/cross-flow velocity) were varied from VR=3, 5 and 7 while the jet velocity was kept constant corresponding to Re=13,400. The experimental investigation was carried out for heat transfer characteristic by using Thermochromic Liquid Crystal sheet, and heat transfer coefficient distributions were evaluated using an image processing method. The results show that the impinging jets with mounting the baffles in the upstream region of jet impingement region can enhance the heat transfer rate throughout VR.

Non-linear Behavior of Normal Contact Stiffness of Tunnel Surface and Supporting System of Tunnel Boring Machines

The interfacial contact stiffness between the supporting system of tunnel boring machines(TBM) and the tunnel surfaces is closely related to the mechanical behavior of rocks and the morphology of tunnel surfaces. The mathematical model based on the fractal theory is employed to study the relation between the roughness and fractal parameters of three dimensional tunnel surfaces. The coarse surfaces are established by using the projecting method according to the characteristics of tunnel surfaces. Many parameters such as the roughness of the tunnel surfaces, the mechanical behavior of rocks, the number of the supporting boots and composite geologic structures are taken into consideration to obtain the correlation between the normal contact stiffness and the loads. The results show that the increases of the fractal dimension, the elastic modulus, the normal loads and the number of support boots cause the increase of the interfacial contact stiffness. The contact stiffness of the double supporting systems is twice of that of the single one subjected to the same load. The normal stiffness is minimal when the ratios of the soft and hard rocks in the composite geologic structures are approximately identical. The increasing of the ratio of soft rocks in the contacting area causes the increase of the contact stiffness. However, the variation of the contact stiffness is not obvious when the proportions of two kinds of rocks on the contacting area are changed.

Volume and contact surface area analysis of bony tunnels in single and double bundle anterior cruciate ligament reconstruction using autograft tendons: in vivo three-dimensional imaging analysis.

BackgroundRegarding reconstruction surgery of the anterior cruciate ligament (ACL), there is still a debate whether to perform a single bundle (SB) or double bundle (DB) reconstruction. The purpose of this study was to analyze and compare the volume and surface area of femoral and tibial tunnels during transtibial SB versus transportal DB ACL reconstruction.MethodsA consecutive series of 26 patients who underwent trantibial SB ACL reconstruction and 27 patients with transportal DB ACL reconstruction using hamstring autograft from January 2010 to October 2010 were included in this study. Three-dimensional computed tomography (3D-CT) was taken within one week after operation. The CT bone images were segmented with use of Mimics software v14.0. The obtained digital images were then imported in the commercial package Geomagic Studio v10.0 and SketchUp Pro v8.0 for processing. The femoral and tibial tunnel lengths, diameters, volumes and surface areas were evaluated. A comparison between the two groups was performed using the independent-samples t-test. A p-value less than the significance value of 5% (p < 0.05) was considered statistically significant.ResultsRegarding femur tunnels, a significant difference was not found between the tunnel volume for SB technique (1,496.51 ± 396.72 mm3) and the total tunnel volume for DB technique (1,593.81 ± 469.42 mm3; p = 0.366). However, the total surface area for femoral tunnels was larger in DB technique (919.65 ± 201.79 mm2) compared to SB technique (810.02 ± 117.98 mm2; p = 0.004). For tibia tunnels, there was a significant difference between tunnel volume for the SB technique (2,070.43 ± 565.07 mm3) and the total tunnel volume for the DB technique (2,681.93 ± 668.09 mm3; p ≤ 0.001). The tibial tunnel surface area for the SB technique (958.84 ± 147.50 mm2) was smaller than the total tunnel surface area for the DB technique (1,493.31 ± 220.79 mm2; p ≤ 0.001).ConclusionsAlthough the total femoral tunnel volume was similar between two techniques, the total surface area was larger in the DB technique. For the tibia, both total tunnel volume and the surface area were larger in DB technique.

H141 トンネル内温熱環境に関する模型実験

To investigate the thermal environment in railway tunnels, temperature predictions by simulation are necessary. The authors made an acrylic model tunnel, sent the heated air inside of the model tunnel and measured the temperatures of the outer surface of the model tunnel and the air in the model tunnel. As a result, we found that it is possible to assume the outer surface temperatures to be isothermic. And, the analytical predictions of the steady state air temperature in the model tunnel showed good agreement with the measured values.

A Temporal Millimeter Wave Propagation Model for Tunnels Using Ray Frustum Techniques and FFT

A temporal millimeter wave propagation model for tunnels is presented using ray frustum techniques and fast Fourier transform (FFT). To directly estimate or simulate effects of millimeter wave channel properties on the performance of communication services, time domain impulse responses of demodulated signals should be obtained, which needs rather large computation time. To mitigate the computational burden, ray frustum techniques are used to obtain frequency domain transfer function of millimeter wave propagation environment and FFT of equivalent low pass signals are used to retrieve demodulated waveforms. This approach is numerically efficient and helps to directly estimate impact of tunnel structures and surfaces roughness on the performance of millimeter wave communication services.

Study on Blasting Technology and Control Measures of Shallow Tunnel

Based on a municipal highway tunnel in western China, for the building of the tunnel surface dense, especially import Portal Jude Biao most shallow depth of less than 10m building project, we proposed borehole layout, charge and detonate Network Road design method, and the corresponding control points of drilling and blasting operations and blasting safety control measures and means to ensure that the duration and quality of construction, can provide some experience of similar projects and basis.

Structural Behavior of FRP Tunnel Lining

This paper represented the numerical analysis of the tunnel lining which was used for maintaining the old tunnel. The tunnel lining was made from FRP corrugated sheet that supported the lining concrete in the tunnel and flowed the water or / and the moisture swept on the tunnel surface. The FRP sheet was supported by the anchor bolts. In numerical analysis, the finite element degenerate shell was adopted to represent the FRP behavior. Firstly, the proposed FRP sheet was adopted and the distribute load equivalent to the concrete peeled from the tunnel lining was applied and the stresses of the FRP sheet, the tensile force of bolts and the deflection of FRP sheet were investigated. Then, secondary, the FRP corrugated sheet with longitudinal cover strip was investigated. From the numerical analysis, the effectiveness of the FRP corrugated sheet was confirmed.

Investigation of the tunneling properties and surface morphologies of BaSi2/Si tunnel junctions for BaSi2 solar cell applications

AbstractThree different tunnel junctions (p+‐BaSi2/p+‐Si, n+‐BaSi2/p+‐Si and n+‐BaSi2/n+‐Si) have been fabricated for the formation of BaSi2 solar cells on Si substrates. Investigation of the tunneling properties and surface morphologies of these tunnel junctions has been done to find out which one is the best. From the current‐voltage characteristics, p+‐BaSi2/p+‐Si tunnel junction showed the greatest current of the three. The surface morphologies revealed that the p+‐BaSi2/p+‐Si tunnel junction has a very smooth surface compared with the other tunnel junctions. Tunnel junction with a smooth surface is a requirement for growing BaSi2 overlayers for BaSi2 solar cells. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Loads on Sprayed Waterproof Tunnel Linings in Jointed Hard Rock: A Study Based on Norwegian Cases

A composite tunnel lining system based on a sprayed waterproofing membrane combined with sprayed concrete is currently being considered for future Norwegian rail and road tunnels. Possible loading of the tunnel linings caused by water pressure is being investigated. This tunnel lining system consists of a waterproof membrane which, during application on the sprayed concrete lining, bonds mechanically to the sprayed concrete on either side. Hence, a continuous, sealing, and non-draining structure from the rock mass to the interior tunnel surface is formed in the walls and crown. Experiences from some successful recent projects with this lining system in Europe are reviewed. However, these experiences are not directly comparable to the Scandinavian hard rock tunnel lining approach, which utilizes a relatively thin sprayed and irregular concrete layer for permanent lining. When considering the sprayed membrane and sprayed concrete composite lining concept, introducing a partially sealing and undrained element in the lining, the experiences with the traditionally used lining systems in Norway need to be reconsidered and fully understood. A review of several hard rock tunnels with adverse conditions, in which the tunnel lining has been subject to load monitoring, shows that only very small loads in the tunnel linings occur. Recent investigations with in situ water pressure testing, including two sites with the composite sprayed membrane in a partially drained waterproof tunnel lining, are discussed. In a case with a cavern located in a hydraulically saturated rock mass subjected to approximately 8 bar hydrostatic pressure, a negative pressure gradient towards the tunnel lining has been measured. The investigation results from the Norwegian test sites indicate that no significant loading of the tunnel lining takes place in a hydraulically saturated rock when applying this composite waterproof tunnel lining in parts of the tunnel perimeter.