ABSTRACT
Urban transport systems using underground space are necessary for attending the needs of increasing urban population. Modern standards, technology and experience are key factors for reliable, fast and safe construction. TBM technology allows successful construction of running tunnels. Station’s and other structure’s construction causes disturbance to the urban environment, limits accessibility and requires traffic or utility diversions. Station’s design shall attend architectural and functionality features, taking in account social-economic impacts during construction. Risk assessment requires a reliable investigation of the subsurface conditions. The design of underground structures should consider all constraints. Including constructability and safety criteria in early design stages reduces risks. Riyadh Metro project includes the design and construction of large diameter tunnels and underground stations. The time schedule required specific solutions in sequencing tunnelling and deep excavations. Stations include construction with pre-cast elements. Some technological challenges for designers and constructors in future projects of underground infrastructures are proposed.
