Noise levels inside the coaches of Greater Cairo tunnel metro, line 3 tunnel

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جزئیات بیشتر

انتشار

۲۰۲۱

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scopus – master journals – JCR

ایمپکت فاکتور

۴٫۲۷۶ در سال ۲۰۲۰

شاخص H_index

۲۶ در سال ۲۰۲۱

شاخص SJR

۰٫۹۰۱ در سال ۲۰۲۰

شاخص Quartile (چارک)

Q1 در سال ۲۰۲۰

مدل مفهومی

ندارد

پرسشنامه

ندارد

متغیر

ندارد

رفرنس

دارد

قوانین استفاده

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توضیحات مختصر محصول
Noise levels inside the coaches of Greater Cairo tunnel metro, line 3 tunnel

فهرست مطالب مقاله:

Abstract

 This paper investigates the noise  inside  a metro coach  running  through the  most recent tunnel of Cairo.  The  study  focuses  on the effects of alignment profiles  on the A- weighted noise  level. Although the latest line  has  not  been studied yet, noise  levels  inside the  old lines  attracted the  attention of researchers due  to their importance as the  first mass transit system in Africa.  Given that windows  are  usually  kept  open, measurements were  con- ducted inside  the empty cabin  at the end  of the train with open  windows  according to ISO

3381:2005. Results  showed  that noise  emissions  inside  the running  coaches are  high and  do not  follow either international or general national legislation, which  presents health hazards for drivers and commuters. Speech  intelligibility is required for train  radio units and driver con- soles for voice communications, which provides a safe working environment for the  train  crew. The present study reveals that tight  curves  mainly  contribute to high noise. The noise  levels are  further raised by the  reflective surface of the tunnel with  a circular cross-section and the  unballasted track. Moreover, the  noise  level  is affected by the  location of the  coach  and window  conditions (open/close) to some  extent.

بخشی از متن مقاله:
  1. Introduction

Railway noise  represents a daily  environmental concern in developed and  developing countries  (Fields  and  Walker,

1982) and  affects the  safety and  health of employees and passengers (Eade, 1999).  The  World  Health   Organization (WHO) indicates that environmental noise  in western Eu- ropean countries, which is estimated at approximately one million  healthy life  years   per   year   due  to  traffic noise, significantly  impacts   the   disability  adjusted   life   years (DALYs) (WHO, 2011).  Hearing  loss is the  most  common  ef- fect caused by exposure to excessive noise according to the

2010  occupational illnesses report.  Noise  resulting  from transportation, including   vehicles,  railway,  and  aircraft, represents  approximately  ۶۰%  of   noise   in   Africa   (UN- Habitat, 2014)  and  the   main  cause of  noise   in  Greater Cairo (Egyptian  Environmental Affairs Agency, 2008). Excessive noise exposure, viruses, and conditions caused by normal  aging are the  main reasons for sensorineural hearing loss,  which  is defined as an  impairment that is associated with  irreversible deterioration to the  inner  ear  and  mostly cannot be healed (OSHA, 2019).  Noise-induced hearing loss (NIHL) represents one of the  common  occupational diseases in different cities  of the  United  States (Bauer  et al., 2001). In addition, a recent study  showed  that exposure to freight train  noise together with its vibration affects the  heart rate during   sleep,  which   may  influence  cardiovascular  func- tioning   (Croy  et  al.,  ۲۰۱۳).   Moreover,  excessive  noise exposure influences human  health in several ways,  such as headache,  insomnia, fatigue,  high  blood  pressure, arrhythmia,  annoyance,  problems with  performance and communications, lowered morale, poor signal intelligibility, and  poor  concentration (OSHA, 2019).

Underground train  noise  can  be  classified into  airborne and  structure-borne noise. Airborne  noise  originates from different  sources, such  as  steel wheel/rail action, train siren/whistle, aerodynamic noise, power  and  auxiliary equipment (such  as  HVAC  systems), power  units, and  en- gines  (Croy et al., 2013).

Structure-borne noise is derived from vibro-acoustic sources radiated  by  vibration transmission into  the   train envelope from  bogies  and  mounted equipment, in  which the  predominant frequencies are mostly below 200 Hz (Choi et al., 2004).  The  emission   of  wheel/rail noise  increases with  the  train  speed and  the  surface roughness of wheel/ rail  contact.  Instead of  cast-iron treaded  brake  stocks, applying  disc  brakes for  rolling  stocks  results in  reduced noise  by 8 dB(A) at speeds of 160 km/h (Eade, 1999). Noise barriers can be an effective countermeasure for mitigating wayside  noise  but  does  not  decrease the  noise  inside  the coaches and  the  driver  cabin  (Eade, 1999).

Noise emission  from  trains arising  between the  wheels and  rails  is influenced by  rail  alignment, lack  of  mainte- nance, and  rigidity  of  track  supports (ARUP, 2015).  How- ever, any  alignment usually  runs  along  narrow   corridors, which  comprises numerous horizontal curves  and  vertical slope  gradients. Such curves  lead  to the  excessive wear  of rails because of the  abrasive action of the  rolling wheels.

Greater Cairo, which is the first of Africa’s megacities and the  second by 2025, has approximately 17 million residents. Northern African  cities, including  Egypt,  experience pollu- tion and congestion because of the  high numbers of private motor  cars  (UN-Habitat, 2014).  Mass public  transport  sys- tems, particularly railway transportation, have been applied to address the needs of overpopulation. Fig. 1 shows that the Great Cairo  Metro  network links  three  governorates with three lines in operation. As of 2020, the  network comprises

68 stations with a total length of 81.6 km. The underground section extends approximately 36 km (roughly  ۴۴% of the total  length) and  mainly  comprises  two  different  cross- sections, namely  cut & cover and circular sections.

 

Line 3 is the  latest in operation despite the  inauguration of only three of its five phases. Upon completion, Line 3 will form the  east-west corridor of the  city, which connects Alf Maskin (east) to Boulak and/or Rod El Farag suburbs  (west). The overall  length of Line 3 will be approximately 34.5 km and comprise 34 stations. The current routing, which is fully located underground, is  ۱۶  km  long  and  includes 13  un- derground stations (National Authority  for  tunnel, 2012a). The  tunnel lots  connecting these stations have  a  circular cross-section.

The  literature on  railway   noise  in  Egypt,  particularly inside   tunnels,  includes some   reports on  this  particular problem despite the  presence of many tunnels in the  Cairo mass transit network, which is currently continuously extended. Thus, studying  the  noise levels along the  existing tunnels is crucial   to  examine the   daily  exposure for  the train   crew  and  passengers and  determine the   influential factors.  Based   on   field   measurements,  this   paper   in- vestigates the  airborne noise  caused by rapid  transit trains inside   the   typical circular tunnel  of  the   newest line  of Cairo’s Metro network.

 

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