Propagation Mechanism Analysis Before the Break Point Inside Tunnels

There is no unanimous consensus yet on the propagation mechanism before the break point inside tunnels. Some deem that the propagation mechanism follows the free space model, others argue that it should be described by the multimode waveguide model. Firstly, this paper analyzes the propagation loss in two mechanisms. Then, by conjunctively using the propagation theory and the three-dimensional solid geometry, a generic analytical model for the boundary between the free space mechanism and the multi-mode waveguide mechanism inside tunnels has been presented. Three measurement campaigns validate the model in different tunnels at different frequencies. Furthermore, the condition of the validity of the free space model used in tunnel environment has been discussed in some specific situations. Finally, through mathematical derivation, the seemingly conflicting viewpoints on the free space mechanism and the multi-mode waveguide mechanism have been unified in some specific situations by the presented generic model. The results in this paper can be helpful to gain deeper insight and better understanding of the propagation mechanism inside tunnel

Propagation mechanism modelling in the near region of circular tunnels

Artículo sobre comunicaciones ferroviarias. Abstract: Along with the increase in operating frequencies in advanced radio communication systems utilised inside tunnels, the location of the break point is further and further away from the transmitter. This means that the near region lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. To begin with, this study analyses the propagation loss resulting from the free-space mechanism and the multi-mode waveguide mechanism in the near region of circular tunnels, respectively. Then, by conjunctive employing the propagation theory and the three-dimensional solid geometry, a general analytical model of the dividing point between two propagation mechanisms is presented for the first time. Moreover, the model is validated by a wide range of measurement campaigns in different tunnels at different frequencies. Finally, discussions on the simplified formulae of the dividing point in some application situations are made. The results in this study can be helpful to grasp the essence of the propagation mechanism inside tunnels

Propagation Mechanism modeling in the Near-Region of Arbitrary Cross-Sectional Tunnels.

Along with the increase of the use of working frequencies in advanced radio communication systems, the near-region inside tunnels lengthens considerably and even occupies the whole propagation cell or the entire length of some short tunnels. This paper analytically models the propagation mechanisms and their dividing point in the near-region of arbitrary cross-sectional tunnels for the first time. To begin with, the propagation losses owing to the free space mechanism and the multimode waveguide mechanism are modeled, respectively. Then, by conjunctively employing the propagation theory and the three-dimensional solid geometry, the paper presents a general model for the dividing point between two propagation mechanisms. It is worthy to mention that this model can be applied in arbitrary cross-sectional tunnels. Furthermore, the general dividing point model is specified in rectangular, circular, and arched tunnels, respectively. Five groups of measurements are used to justify the model in different tunnels at different frequencies. Finally, in order to facilitate the use of the model, simplified analytical solutions for the dividing point in five specific application situations are derived. The results in this paper could help deepen the insight into the propagation mechanisms in tunnels

Modeling of the Division Point of Different Propagation Mechanisms in the Near-Region Within Arched Tunnels

An accurate characterization of the near-region propagation of radio waves inside tunnels is of practical importance for the design and planning of advanced communication systems. However, there has been no consensus yet on the propagation mechanism in this region. Some authors claim that the propagation mechanism follows the free space model, others intend to interpret it by the multi-mode waveguide model. This paper clarifies the situation in the near-region of arched tunnels by analytical modeling of the division point between the two propagation mechanisms. The procedure is based on the combination of the propagation theory and the three-dimensional solid geometry. Three groups of measurements are employed to verify the model in different tunnels at different frequencies. Furthermore, simplified models for the division point in five specific application situations are derived to facilitate the use of the model. The results in this paper could help to deepen the insight into the propagation mechanism within tunnel environments

Propagation Characteristics of International Space Station Wireless Local Area Network

This paper describes the application of the Uniform Geometrical Theory of Diffraction (UTD) for Space Station Wireless Local Area Networks (WLANs) indoor propagation characteristics analysis. The verification results indicate good correlation between UTD computed and measured signal strength. It is observed that the propagation characteristics are quite different in the Space Station modules as compared with those in the typical indoor WLANs environment, such as an office building. The existing indoor propagation models are not readily applicable to the Space Station module environment. The Space Station modules can be regarded as oversized imperfect waveguides. Two distinct propagation regions separated by a breakpoint exist. The propagation exhibits the guided wave characteristics. The propagation loss in the Space Station, thus, is much smaller than that in the typical office building. The path loss model developed in this paper is applicable for Space Station WLAN RF coverage and link performance analysis

Large-scale fading characterization in curved modern subway tunnels

This paper presents extensive propagation measurements conducted in a modern arched tunnel with 300 m and 500 m radii of curvature with horizontal polarizations at 920 MHz, 2400 MHz, and 5705 MHz, respectively. Based on the measurements, statistical metrics of propagation loss and shadow fading in all the measurement cases are extracted. Furthermore, for each of the large-scale fading parameters, extensive analysis and discussions are made to reveal the physical laws behind the observations. The quantitative results and findings are useful to realize intelligent transportation systems in the subway system

Propagation and Wireless Channel Modeling Development on Wide-Sense Vehicle-to-X Communications

The need for improving the safety and the efficiency of transportation systems has become of extreme importance. In this regard, the concept of vehicle-to-X (V2X) communication has been introduced with the purpose of providing wireless communication technology in vehicular networks. Not like the traditional views, the wide-sense V2X (WSV2X) communications in this paper are defined by including not only vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications but also train-to-X (T2X) communications constituted of train-to-train (T2T) and train-to-infrastructure (T2I) communications. All the information related to the wide-sense V2X channels, such as the standardization, scenarios, characters, and modeling philosophies, is organized and summarized to form the comprehensive understanding of the development of the WSV2X channels

Measurements and analysis of large-scale fading characteristics in curved subway tunnels at 920 MHz, 2400 MHz, and 5705 MHz

ave propagation characteristics in curved tunnels are of importance for designing reliable communications in subway systems. This paper presents the extensive propagation measurements conducted in two typical types of subway tunnels—traditional arched “Type I” tunnel and modern arched “Type II” tunnel—with300- and 500-m radii of curvature with different configurations—horizontal and vertical polarizations at 920, 2400, and 5705 MHz, respectively. Based on the measurements, statistical metrics of propagation loss and shadow fading (path-loss exponent, shadow fading distribution, autocorrelation, and cross-correlation) in all the measurement cases are extracted. Then, the large-scale fading characteristics in the curved subway tunnels are compared with the cases of road and railway tunnels, the other main rail traffic scenarios, and some “typical” scenarios to give a comprehensive insight into the propagation in various scenarios where the intelligent transportation systems are deployed. Moreover, for each of the large-scale fading parameters, extensive analysis and discussions are made to reflect the physical laws behind the observations. The quantitative results and findings are useful to realize intelligent transportation systems in the subway system

A preliminary study on wire sawing and its comparison with the traditional drill and blast method

Abstract. The traditional drill and blast method has been the most common excavation method for excavating underground spaces. It is an effective method in terms of costs and productivity. However, in certain situations, blasting cannot always be used. For example, excavation close to a sensitive area where blasting may cause vibrations must be restricted. Wire saw cutting used together with the drilling and blasting method is an alternative. As wire saw cutting is a relatively new technique for tunnelling, this thesis aims to provide a comprehensive literature review on this method based on previous studies. The purpose of the thesis is to present detailed information and data on the effectiveness and productivity of the wire saw cutting method, the mechanism of saw cutting, the forces of saw cutting and other important parameters related to the use of wire saw cutting. In addition, the theory of blasting vibrations and the effect of pre-cut discontinuity made by wire saw cutting on vibration reduction are discussed. The research also included a site visit and where wire saw cutting together with drilling and blasting were used in tunnel excavation. This study offers extensive knowledge on wire saw cutting and its current state. Based on the literature review and the site visit, the most common advantages and problems of the method are presented. This knowledge can be used in future research to improve the use of wire saw cutting.Tiivistelmä. Perinteisimmin maanalainen louhinta suoritetaan käyttämällä poraus- ja panostusmenetelmää. Menetelmä on tehokas sekä kustannusten että aikataulun osalta. Tietyissä tilanteissa kyseistä louhintamenetelmää ei kuitenkaan pystytä käyttämään perinteiseen tapaan. Tällainen tilanne voi olla esimerkiksi louhinta alueella, jossa räjähdyksen aiheuttamia tärinöitä täytyy rajoittaa lähellä sijaitsevien tärinäherkkien laitteiden tai rakennusten vuoksi. Vaijerisahaus käytettynä yhdessä poraus- ja panostusmenetelmän kanssa on yksi vaihtoehto tärinöiden rajoittamiseksi. Vaijerisahauksen käyttö tunnelikohteissa on suhteellisen uusi louhintamenetelmä. Tästä syystä tämän tutkielman tarkoituksena on tuottaa kattava kirjallisuuskatsaus menetelmän käytöstä. Työssä esitetään tietoa menetelmän tehokkuudesta ja tuottavuudesta, leikkausmekanismiin sekä leikkausvoimiin liittyvää teoriatietoa sekä muuta tärkeää informaatiota menetelmään ja sen käyttöön liittyen. Tämän lisäksi työssä käsitellään räjäytystärinöitä sekä niiden etenemistä kallioperässä. Tämän pohjalta pohditaan vaijerisahauksella leikatun uran vaikutusta räjäytystärinöiden etenemiseen. Työn aikana suoritettiin myös vierailu tunnelityömaalle Ruotsiin, jossa vaijerisahausta käytettiin poraus- ja panostusmenetelmän apuna räjäytystärinöiden vähentämiseksi. Työn tavoitteena on tarjota laaja katsaus vaijerisahaukseen ja sen nykyiseen tilaan kalliorakentamisen kohteissa kirjallisuuden ja työmaavierailun pohjalta. Tulevissa tutkimuksissa tätä tietoa voidaan hyödyntää kyseisen louhintamenetelmän kehittämiseen

Air Intrusion on Pipe-filling Bores in Quasi-horizontal Pipelines

https://deepblue.lib.umich.edu/bitstream/2027.42/154157/1/39015099114822.pd