164 X2 Category 2: Civil Structures Project description Ceintuurbaan Station is part of the North/South line project, situated in the historic centre of Amsterdam. The scope of the project contains eight stations and connects the northern and southern districts with the city centre. The metro line measures approximately 10 km in length, divided into an underground section of 7 km and a bored tunnel of 3 km long. The metro line runs from the above-ground Buikslotermeerplein Station via a semisunken route and is connected with the Central Station by an immersed tunnel below the IJmeer. From the Central Station, the metro line continues its route via the stations Rokin, Vijzelgracht and Ceintuurbaan. These stations are all constructed at an average depth of 30 m below the surface and are connected by a bored tunnel. At Europaplein Station the metro arrives above the ground and is connected to the existing metro network at Zuid/WTC Station. Structure and building method Ceintuurbaan Station is 230 m long and has an average width of 11 m. Due to the limited space available between the buildings at street level, the station is designed for two bored tunnels, which are located above each other. The station has two main entrances through which passengers can enter the station at NAP +0.6 m. From the concourse level at NAP -6.8 m, passengers (approximately 42,500 a day) are divided over the two lower platforms by an escalator or elevator. To minimise the duration of the impact on traffic and the surroundings, the station is built by using the cut & cover method. First, the diaphragm walls, 1.2 m thick, and the roof were made. Below the roof structure more excavation took place, while constructing several floors and metro platforms. To guarantee the vertical stability of the deepest section, the last couple of metres were excavated under compressed air, starting from the intermediate floor at NAP -18.8 m. After the completion of the foundation slab, the concrete structure was ready to be connected with the bored tunnels. Horizontal stability of the structure During the excavation process, the diaphragm walls were supported by temporary steel struts at different levels to secure horizontal stability. Due to its great depth and the presence of several openings in the floor slabs, the combination of diaphragm and retention walls also has to be supported by additional struts in the final phase. These struts are applied at five different levels. The permanent steel struts are installed and prestressed in the presence of the temporary steel struts and floor slabs. The temporary steel struts are removed in different phases. During removal, the deflection of the steel struts is monitored by strain gauges and extensometers. With the information obtained from these measuring instruments, the forces per construction stage can be determined. Use of Scia Engineer To verify these results, a 3D model of the station is created in Scia Engineer. With the use of the module ‘construction stages’, the influence of the several construction phases could be predicted. This gave the opportunity to verify the retrieved information from the monitoring. Furthermore, the model made it possible to anticipate critical situations and to prevent the forces from exceeding the design values in the consecutive stages. Software: Scia Engineer Ceintuurbaan Station, North/South Metro Line - Amsterdam, The Netherlands
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