Comparative Evaluation of Alternative Methods for the Construction of Underground Car Parks

The present paper focuses on the comparison between the alternative methods of constructing underground parking spaces. It analyses and compares the “cut-and-cover” method, a most common method for the construction of underground parking stations, with the “room-and-pillar” method originating from the mining sector which also exhibits equally satisfactory results. This evaluation takes into account the applicability of each method in relation to the ground conditions, their ease of use, as well as their performance in terms of financial efficiency during construction. The assessment is made using reference projects as input. More specifically, the construction costs of three underground car-stations, constructed with the “cut-and-cover” method are compared with the construction costs of three other underground car-stations which were designed following the “roomand-pillar” method principles. Their key elements are recognized and major cost components are evaluated in a head to head analysis. 1. IMPORTANCE OF PARKING SPACES – UNDERGROUND CAR PARKS Car plays an important role to modern societies as it is a comfortable and fast mean of transport. However, its usefulness and service degree depends particularly on the sufficiency of suitable parking spaces. The importance of “parking” is evident from the space that is provided and the time that a car is found parked in relation to the time of its movement. Thus, a passenger car requires a parking area of approximately 25 m 2 , including the essential areas for gaining access and manoeuvres, while the time it remains parked is more than 90% of the total. However, the lack of parking spaces is one of the most significant problems that large urban centres face today. This fact has lead to particularly negative consequences in the life and style of the cities because of the traffic jams and long delays, as well as the environmental pollution. The utilisation of the subsurface with the establishment of underground car parks has been proposed as a measure to alleviate the lack of parking space in urban areas and today, along with the underground transit systems (metros, etc.), can be characterised as the most typical form of underground development (Kaliampakos D., 2003). The advantages that such facilities offer are significant (ITAWG13, 1995; Sterling, 1997) and their use is widespread. In particular, they contribute to the environmental protection, as valuable surface space can be preserved and the visual annoyance is minimal, assisting in the improvement of the quality of the city life (Tareau, J.P., 1995), and at the same time they can provide a safe environment with high availability since their construction could take place almost anywhere. Nevertheless, underground car parks have to deal with a high construction and service cost, in relation to aboveground solutions, because of the increased need for support, lightning and ventilation. That issue puts forth the necessity to further investigate solutions capable of offering lower costs without on the same time affecting the efficiency of underground car parks.