Underground Lines Research Articles

Identifying the influence of a large alluvial valley on train-induced vibration propagation in Rome by an integrated approach

In recent decades, the number of tunnels has increased within city centres worldwide due to the construction of new underground train lines, thus instigating subsequent issues related to an increase in the amount of vibrations affecting pre-existing buildings and infrastructures; therefore, more studies have been devoted to investigating the interactions between underground train lines and buildings within the framework of a site-city interaction (SCI) scheme. The already designed layout of line C of the Rome Metro was chosen as the research object of a case study focusing on underground train-induced vibration propagation in the city centre of Rome (Italy). Numerical modelling was carried out to analyse the propagation of future vibrations within the large buried alluvial valley and to assess the spatial extension of the induced vibration resentment.Two different subsoil models were considered for this study area: i) a homogeneous model (HoM), in which a homogeneous filling of Tiber alluvia was considered, and ii) a heterogeneous model (HeM), where the Tiber alluvia was distinguished within various lithotechnical units. Specific geophysical measurements were performed to i) record vibrations induced by accelerating, braking and regularly transiting trains to provide input for numerical modelling and ii) define the typical ambient vibration noise of the investigated area. Numerical modelling was then performed using the CESAR-LCPC code, which adopts a finite element method (FEM) solution in the time domain, to simulate the propagation of train-induced vibrations within the Tiber River valley in both the HoM and HeM simulations.The simulation outputs reveal a negligible deamplification effect up to approximately 2 Hz with respect to the considered solicitation in the area located above the tunnels and a maximum effect with respect to the reference ambient vibration noise within 5 and 10 Hz along the valley. The vibrations induced by the accelerating trains can be associated with the highest resentment at the free surface of the valley. A more intense effect generally results in the HeM simulation, which highlights the nonnegligible role of the heterogeneities present within the Tiber alluvia in propagating train-induced vibrations. The numerical outputs highlight that the train-induced vibrations can propagate hundreds of metres away from the underground train location, i.e., up to 400 m astride the axis of the designed tunnels in the case study considered here, and can be distinguished with respect to the regular ambient vibration level.

РОЗПОДІЛ МАГНІТНОГО І ТЕПЛОВОГО ПОЛІВ ТА ВТРАТИ ПОТУЖНОСТІ В ЕЛЕКТРОМАГНІТНОМУ ЕКРАНІ ПІДЗЕМНОЇ ДВОКОЛОВОЇ КАБЕЛЬНОЇ ЛІНІЇ

In the article, the magnetic and thermal field distributions generated by underground two-circuit extra-high voltage power cable line in the environment, particularly near the cables and flat aluminum shield, which is located at a different distance from the cables and has different thicknesses, are analyzed. The unique features of the magnetic field and temperature distributions inside the shield are computed and studied. For the cases under consideration, the Joule losses in the external shield do not exceed 3% of the losses in the cables. The primary electromagnetic characteristics are compared for the aluminum shield (shielding efficiency is 1,94) and the shield with lower conductivity (shielding efficiency is equal to 1,2). As shown, the thicker shield helps to increase the ampacity of the cable line owing to lower heating. The actual operating current of the cable line under consideration depends on the distance of the shield from the cables owing to the relation between their maximum temperature and this distance. Ref. 15, fig. 7, table.

SPECIFICS OF DIAGNOSTICS OF TECHNICAL CONDITION OF TRANSPORT AND TECHNOLOGICAL SYSTEM “MINING GAS PIPELINE – MINE WORKING”

The purpose of the paper is to analyze a deformation mechanism of the mine degassing pipelines to forecast their spatial changes in terms of intensification of underground mining of coal-gas seams.
 Methodology. The paper deals with expert assessment of the available approaches to diagnostics of technical condition of mine degassing pipelines, which are constructed within the in-seam underground mine workings with the floor rocks prone to heaving. The results of scheduled surveying measurements of technical condition of in-seam development workings have helped identify the potentially hazardous zones of rock mass deformation and indices of changes in spatial location of section degassing pipelines mounted in those mine workings. To determine the operating modes of a degassing pipeline under such operating conditions, a computer model of interaction of the elements of transport-technological system “mine gas pipeline – mine working” has been developed
 Findings. Diagnostics of technical conditions of the mine gas transmission lines and examination of their dismantled components have helped understand that deflections, mainly resulting in water accumulation zones, intensive corrosion of internal pipe walls, and mechanical depositions of coal and rock dust take place right within the flange connection areas. Formation of such zones is argued by health of the degassing pipeline as well as mine air inflow. Availability of internal corrosion, water accumulations, and mine air inflow decreases substantially capacity of the underground gas transmission line inclusive of qualitative characteristics of the captured methane-air mixture and efficiency of MDS on the whole.
 Originality. New approaches to diagnostics of technical condition of mine degassing gas pipeline in difficult mining and geological conditions of development of gas-bearing coal seams are substantiated and it is offered to consider indicators of their functioning as interacting in space and time transport-technological system "mine gas pipeline - mining".
 Practical implications. The operational parameters of mine degassing systems notes that the equipment performance with the least underpressure losses created by vacuum pipes requires that the degassing pipeline should have minimum hydraulic resistance of the gas transmission network. Pipeline aeration from the mine workings and water accumulations should be prevented by means of qualitative hermetic sealing of its flange connections as well as the pipeline straightness with the corresponding pitches. Consequently, the basic requirements for operating mine degassing pipelines involve their design profile, tightness of flange connections of pipes as well as operative control of the facility health.

Identification of Fault in Invisible Underground Broken Transmission Lines

ABSTRACT The underground electricity distribution cables are subjected to stress and pressure as they are laid underneath the earth. Due to many factors, these cables create different types of faults that include short circuits. If these faults are not addressed, the power supply is disrupted and resulting in permanent damage. To deal with faults in underground cables, a device has been devised that includes detection of underground broken wires using an android application. The suggested approach measures the electric field around the underground wire. This approach differentiates the short circuit fault from other kinds of faults in underground cables. Only methods for detecting short circuit errors are considered in standard fault detection techniques. The proposed system makes use of low-cost electronic devices that are simple to construct. As a result, the proposed underground fault detection product provides a low-cost optimization solution to locate short-circuit defects.

On the Power Lines—Electromagnetic Shielding Using Magnetic Steel Laminates

Protection against the electromagnetic fields around high-voltage transmission lines is an issue of great importance, especially in the case of buildings near power lines. Indeed, the developed fields can be harmful for the habitants and electrical/electronic devices, so the implementation of appropriate measures to address the above electromagnetic interference issue is necessary in order to ensure the safety of both human beings and equipment. Several practices have been proposed to reduce the electric and the magnetic fields around overhead and underground transmission lines (minimum distance, shielded cables, anechoic chamber etc.). In this context, the scope of the current paper is the use of highly permeable magnetic sheets for shielding purposes, along with the development of an appropriate procedure, based on finite element analysis (FEA) for the efficient design of passive shielding. The simulation results are compared with laboratory measurements in order to confirm the adequacy of the proposed methodology. The good agreement between the FEA outcomes and the experimental results confirms that the developed FEA tool can be trustfully used for the design of the shielding means in the case of overhead or underground power lines.

Учредяване на вещни права върху земеделските земи

According to the provisions of Article 56 (1) of the Regulation on the Application of the Law on the Conservation of Agricultural Land /www.lex.bg/, the construction of sites - public property of the state or municipalities - is possible to use agricultural land. This use extends within a certain period of time and takes place outside the site (track) of the site. Temporary use of agricultural land is related to the need for similar land plots in the construction of mostly underground and aerial linear objects and, if necessary, by conducting geological and other surveys. According to the text of Article 64, paragraph 1 of the Law on Energy /www.lex.bg/, the servitudes arise in the extension of existing and under construction of new air and underground power lines, over ground and underground hydrotechnical facilities for the production of electricity, heat transmission lines, gas pipelines, oil pipelines and oil pipelines in favor of the persons who will build and operate the energy site. The emergence of servitudes is closely related to spatial planning as they are an element of the spatial structure. According to the text of Article 64 (4) (1) of the Law on Energy, servitudes arise when there is a detailed development plan which determines the location of the respective properties. As stated in Article 66 of the Energy Act, the type and location of the energy sites and of the areas of service land included within the limits of the servitudes under this Act shall be determined in general and detailed development plans.

The value of additional data for public transport origin–destination matrix estimation

Passenger origin–destination data is an important input for public transport planning. In recent years, new data sources have become increasingly common through the use of the automatic collection of entry counts, exit counts and link flows. However, collecting such data can be sometimes costly. The value of additional data collection hence has to be weighed against its costs. We study the value of additional data for estimating time-dependent origin–destination matrices, using a case study from the London Piccadilly underground line. Our focus is on how the precision of the estimated matrix increases when additional data on link flow, destination count and/or average travel distance is added, starting from origin counts only. We concentrate on the precision of the most policy-relevant estimation outputs, namely, link flows and station exit flows. Our results suggest that link flows are harder to estimate than exit flows, and only using entry and exit data is far from enough to estimate link flows with any precision. Information about the average trip distance adds greatly to the estimation precision. The marginal value of additional destination counts decreases only slowly, so a relatively large number of exit station measurement points seem warranted. Link flow data for a subset of links hardly add to the precision, especially if other data have already been added.

Using IoT Applications for Detection and Monitoring of Underground Cable Fault

Due to underground environments, wear and tear, rats, etc., underground cables are vulnerable to a large range of faults. It's difficult to diagnose the cause of the fault and the whole cable must be separated from the ground to inspect and repair faults. The project work is intended to use the ESP32 controller for detecting the fault location in underground cable lines from the base station in kilometres. The cable needs to be checked for faults to find a fault in the cable. The basic principle of Ohms law is used in this prototype. The current will vary based on the cable 's fault length. In big cities, instead of overhead wires, the electrical cables run underground. It is hard for detecting the precise location of the fault for the repairing phase of that specific cable if the fault occurs in it underground cable. The suggested device finds the precise the fault position. The system is designed with a group of resistors representing cable length in km and a set of switches are generated to cross check the accurateness of the same at any known distance. The voltage across series resistors changes accordingly in the case of a problem, which can then be transferred to an ADC to produce accurate digital data by using programmed C++ that further displays fault position in the distance. The distance, phase, & time of the fault is shown on a computer or mobile device using the internet. The IoT is used to show information on the internet by using ESP32 WiFi module. The website is generated using HTML coding and the fault information is displayed on the website.

An efficient prediction model for vibrations induced by underground railway traffic and experimental validation

This study proposes an efficient prediction model for the vibration generated by underground railways. The proposed model is based on an analytical approach for a tunnel in a horizontally multi-layered half-space, showing the advantage of high computational efficiency and accuracy. Three alternative modelling strategies regarding hypotheses about the cross-section behavior of the slab and the connection condition between the slab and tunnel are introduced. A multi-body vehicle model is subsequently coupled with the track-tunnel-ground system in the moving frame of reference to determine the train-induced vibration. The predicted vibrations on the track, tunnel, and ground surface induced by the passage of trains are compared with the measured vibrations from an underground railway line in London from the literature. The predicted results for the double-beam track model with uniform support and the continuum track model exhibit a good agreement with the site measurements. The cross-section deformation of the track can be ignored and has little influence on the responses of the tunnel and ground. However, the assumption of the one-line connection between the slab and tunnel results in an overestimation of the track vibration, up to 20 dB, and an underestimation of the tunnel and ground vibration, up to 10 dB.

Compressive strength and thermal properties of sand–bentonite mixture

Abstract Sand–bentonite mixtures are used in road embankments as a protective material for protecting underground high-voltage cables and utility pipelines supplying water and gas etc. The sand–bentonite mixtures provide benefits while laying high-voltage cables. The purpose of this study is to determine the proportions as well as mechanical and thermal properties of a dry-mixed sand–bentonite mixture and to investigate the suitability of such mixtures for installation around high-voltage underground power lines in road embankments. When selecting a sand–bentonite mixture, the following requirements must be ensured: the compressive strength must be greater than 0.5 MPa after 24 h; the thermal resistivity must be greater than 1.2 K m/W (thermal conductivity 0,833 W/(K m)); and the moisture content of the sand–bentonite mixture must be less than 13%. The following materials were used when selecting the bentonite mixture: bentonite, 0–4.0 mm fraction sand, cement (CEM I 42.5R), and water. In this study, six groups of samples were formed, in which the parts of concrete, sand, cement, and water were added in different proportions. The strength and thermal conductivity of the samples were analyzed. Studies about the use of bentonite around high-voltage cables have revealed the need for wet mixing of bentonite suspensions. The required thermal conductivity properties of the soil were not achieved by dry mixing. This method of mixing can be useful only in cases when the thermal conductivity of the mixed soil is not relevant, because the work can be continued after a day.

Numerical Analysis of Tunnel Support System at Pune Metro

Pune has witnessed enormous industrial growth, rapid urbanization in the recent past and has put the city's travel infrastructure to stress. Being a densely populated area, Pune's traffic needs cannot be met by road-based transportation systems and additional flyovers. Considering this, the Pune Metro project a strong public transport system partly elevated, and partly underground Line 1 and the completely elevated Line 2 has been discussed and undertaken by Maha Metro Rail Corporation. With the rise in demand, the responsibility for a safe and efficient public transport system also increases hence proper planning, designing, and execution play a vital role. The underground tunnel stretch of the Pune Metro Line 1 project is carried out by TBM and by segmental lining as a support system. By geotechnical parameters and FEM, RS2 software author analyses the ground behaviour and support system and conveys a basic understanding of ground behaviour and results in guidelines for designing the underground tunnel.

Electromagnetic Field Exposure in Kindergarten Children: Responsive Health Risk Concern.

Long-term exposure to physical agents can be detrimental to children due to their vulnerability. This study aimed to assess and compare the electromagnetic field (EMF) exposure level around the kindergartens from the underground transmission line (UGTL). We investigated randomly selected 24 kindergartens based on the location of the UGTL. The EMF emission levels were measured using an EMDEX II (Electric and Magnetic Digital Exposure Meter). The maximum mean value of the EMF emission level was 13.5 mG around the kindergartens and 17.7 mG from the point of UGTL to kindergartens. EMF emission level around the kindergartens was significantly associated with the location of the UGTL (t = −7.35, P < 0.001). These estimates are not trivial, as long-term exposure to EMF among kindergarten children can lead to different health problems. Routine monitoring of EMF emission levels is recommended including the awareness of EMF exposure to public citizens.

ОСОБЛИВОСТІ ЕКРАНУВАННЯ МАГНІТНОГО ПОЛЯ ПІДЗЕМНОЇ ТРИФАЗНОЇ КАБЕЛЬНОЇ ЛІНІЇ ЗА ДОПОМОГОЮ НАСИПНОГО КОМПОЗИЦІЙНОГО ҐРУНТУ З МАГНІТНИМИ ВЛАСТИВОСТЯМИ

The computations of the magnetic field generated by high-voltage (330 kV) underground power cable line with special fill-up soil having different dimensions (bulk) are carried out by the two- and three-dimensional computer models. The supplementary soil above the cables is the composite material with effective magnetic properties and serves as a magnetic shield. The computer results obtained by 2D and 3D models are compared. The efficiency of magnetic field shielding depending on the magnetic permeability, width, and height of the fill-up soil is studied. As revealed, there is the optimal small soil height for the best magnetic field mitigation on the top of the ground directly over the cable line. In addition, the width of the magnetic soil has an appreciable effect on shielding efficiency. The shielding of underground single-circuit three-phase power cable lines is efficient only when using the magnetic fill-up soil (or ordinary external screen made of magnetic materials) with enough small height. References 14, figures 7.

A Study of Fast Front Transients of an HVDC Mixed Transmission Line Exposed to Bipolar Lightning Strokes

Bipolar lightning strokes are associated with multiple polarity electrical discharge with no current intervals in between, making their behavior quite peculiar. This work presents a fast front analysis of a mixed high voltage direct current (HVDC) transmission link, evaluating the factors that influence the line transients due to shielding failures and backflashovers (BFOs), considering both overvoltage and repeated polarity reversal at the cable sending terminal. The research process includes a detailed modeling of a bipolar lightning stroke, frequency-dependent HVDC overhead, and underground transmission line sections. Noticeable findings include the occurrence of only a positive polarity insulator BFO for the adjacent and subsequent tower, despite the dual polarity of the lightning stroke with relatively small values for the lightning parameters. The influence of traveling waves on the insulator flashover performance of the line with varying parameters (such as the riser section length, the tower grounding impedance, and the location of the lightning stroke) is recorded and explained.

Dosimetry analysis of the magnetic field of underground power cables and magnetic field mitigation using an electromagnetic shielding technique

Non-ionizing dosimetry investigations of extremely low frequency (ELF) magnetic fields that are generated by underground power cables as well as the minimization of their health effects are significant topics handled by numerous researchers. In this study, ELF magnetic fields and current densities caused by three-phased underground transmission lines induced in the human model were examined utilizing both analytical and numerical methods. Analyses were carried out using a two-dimensional problem scenario for the comprehensive head and body model. The results of the finite element method (FEM)-based simulation studies and the analytical calculations are consistent with each other. Moreover, a magnetic field shielding method utilizing conductive material was presented in the study. The shielding technique performed with copper material was carried out to mitigate the magnetic field and possible dosimetry hazards in the ELF region. The proposed shield was a 4-mm reverse U-shaped copper material.

The effect of soil thermal conductivity and cable ampacity on the thermal performance and material costs of underground transmission line

This paper presents an optimisation of material costs of a 400 kV cable line arranged in a flat formation for different values of soil thermal conductivity and cable ampacity. The Finite Element Method is adopted to calculate the temperature field within the cable system. The Particle Swarm Optimisation method is used to minimise the material costs of the cable system. To ensure safe and reliable operation of the cable line, the temperature of the cable core should be lower than 90 °C. Under this assumption, the design optimisation is performed to calculate the optimum size of cable bedding cross-sectional area and select the nominal cable conductor area correctly. An application of two commonly used cable backfill materials is studied: Fluidized Thermal Backfill and Sand-Cement Mix. The calculations are performed for current rating varied from 1,000 A to 1,400 A, and thermal conductivity of soil varied from 0.6 W/(m × K) to 1 W/(m × K). The results showed that for a low soil thermal conductivity, i.e. 0.7 W/(m K), it is possible to reduce the overall material cost of the system (cables cost and thermal backfill material cost) when applying Fluidized Thermal Backfill (FTB) instead of commonly used Sand-Cement Mix. The reason is that FTB application allows reducing the cross-sectional area of power cables, which cost has a major effect on the overall material cost of the underground transmission line.

ROMANITIES CLAIMING SUSTAINABILITY: THE CHALLENGE OF PRESERVING URBAN AND ARCHAEOLOGICAL ENVIRONMENT IN THE CONTEXT OF PUBLIC PROCUREMENT PROCESS

Taking as starting point some peculiarities of the archaeological and urban environment involved in the planning of Rome new underground line – what we mentioned as “romanities” –, this article proposes some reflections on the topic of sustainable public procurement and its strategic use as privileged instrument for the promotion of horizontal public policies in the light of the European Union normative paradigm on the matter. The article brings a definition of sustainable public procurement and presents the European Union normative framework that offers a wide juridical legitimisation to the institution as a parameter that must orientate the decisions of the contracting authorities. Furthermore, it demonstrates from a case study how public policies for ecological and cultural protection can be legitimately introduced into public procurement procedures. The case study involves the construction of a new subway line (Line C) – the most modern infrastructure of public transportation of this kind in Italy –, and how it seems to be contributing to the growth of the levels of sustainability of the cultural and urban environment for the benefit of Rome.

Metro Cable Negligence Disclosure using IOT

Underground links are inclined to a wide assortment of flaws because of underground conditions, mileage, rodents and so on diagnosing the shortcoming source is troublesome, and whole link ought to be taken out from the beginning check and fix flaws. The venture work is proposed to identify the area of deficiency in underground link lines from the base station in km utilizing an Arduino regulator. To find an issue in the link, the link should be tried for flaws. The current would fluctuate contingent on the length of flaw of the link. In the metropolitan regions, the electrical links run in underground rather than overhead lines. At whatever point the flaw happens in underground link it is hard to distinguish the specific area of the issue for interaction of fixing that specific link. In case of fault, the voltage across changes accordingly, which is then fed to an develop precise digital data to a programmed Arduino that further displays fault location in distance. The fault occurring distance, phase, and time is displayed on a LCD interfaced with the microcontroller. Internet of things (I.O.T.) is used to display the information over Internet using the personal computer (P.C).

GEOLOGICAL LINE SELECTION OF XIANSHUIHE STRUCTURAL ZONE OF SICHUAN-TIBET RAILWAY

The Kangding segment of the Sichuan-Tibet Railway passes through the Xianshuihe active structural system, where a series of significant engineering geological problems exist such as intensive earthquake and active faults, high-level slippage flow, unstable high and steep bank slopes, high geostress, rockburst and large deformation, high geo-temperature and high stress water inrush. This segment possesses the greatest seismic and geological risks. and it is to find proper reference. Based on the selecting process for ten years, we have chosen the feasible and safe plan of the Sandaoqiao station, Zheduoshan crop and Zheduoshan Mountain tunnel. In this study, through a systematic geological line selection in the Xianshuihe structural belt, we sum up the geological line selection should follow the order of regional stability line selection, engineering geological disasters over ground line selection, very difficult engineering geological problems in underground engineering geological line selection, integrated geological line selection, cross line selection etc. Based on the fundamental line selection, structure, lithology and groundwater should be considered. Giving priority to give way and then passing through are suggested in the deep and large fault. Considering the effects of lithology, defective engineering rock mass(soluble rock, alteration rock and structural soft rock) should be avoided and the hard engineering rock mass is preferred. Considering groundwater, karst groundwater area should shorten the length of horizontal circulating band, groundwater rich area should build line in side and high areas and discharge groundwater along slope, geothermal anomaly area should choose low temperature gallery. This achievement can provide a reference for the constructions of the Jinshajiang suture and Jiali structural belt of the Sichuan-Tibet railway and planed Yunnan-Tibet railway.

Life cycle cost assessment method considering multiple factors for economic evaluation of cable line steel brackets

In China, the bracket of underground high voltage cable transmission line is mainly made of various carbon steels. However, no unified standard exists for type selection of cable brackets in practice. Here, a selection method of the bracket based on life cycle cost assessment is proposed from the viewpoint of technical economy, in which the size of brackets, steel grade, carbon steel corrosion and eddy current loss are considered as influencing factors to the costs. Stress performance analysis under identical pole arm stress constraints is employed to determine the size and grade of carbon steel which influences the initial cost. And 3D coupled electromagnetic fluid-dynamical and thermal finite-element analysis is applied to calculate the eddy current loss of cable brackets which influences the operation cost. Meanwhile, multi-physics coupling analysis and experiment are conducted to prove the correctness of loss simulation calculation. Tafel curve measured by electrochemical corrosion experiment is used to obtain the corrosion rate of carbon steel which influences the maintenance cost by affecting service life of brackets. A case study is demonstrated, and the results show that the channel steel type is the most economical for the commendatory and the proposed method is effective.