Optimal Selection of Underground Parking Lines Arrangement: A Case Study of Tehran Subway Line 7

Due to the development of urban subway lines in order to extend public transportation and to accommodate the increased number of trains, depot and parking are necessary. this is to provide a space for parking trains in non-operating hours and to carry out maintenance and repair operations on trains. subway depot is a predetermined space where trains, washing, car parks, and refueling work are performed. this space can be designed either underground or at-grade according to the existing conditions. these depots and parking occupy a large part of urban land. due to the rapid growth of urbanization and with considering the value and importance of at-grade land for social and economic development, the problems of possession of at-grade spaces and also the lack of suitable urban area in some parts of the cities, the construction of underground depots is an idea against at-grade depots. therefore, in this study different development modes of underground depot and parking are investigated. for this purpose, the north parking of tehran subway line 7 is selected for the case study. each development mode includes a twoline tunnel, two separate one-line tunnels, four separate one-line tunnels and a large span tunnel with four lines together compared by analytic hierarchy process (ahp) and the best option was chosen. in order to investigate the feasibility of implementing the best choice, geotechnical analyses are performed by using plaxis 2d software.