91 Noord/Zuidlijn, station Voorplein, part of Central Station Amterdam Introduction The CS underground station of the North/South Line is on Station Island. This station will be an integral part of the biggest public transport hub in the Netherlands and will provide transfer facilities between local, regional and international public transport systems. The underground stations’ concourse is being built under the main square in front of Amsterdam CS. There are entrances on ground level on both sides of the main entrance of the railway station and one at the south side of the station (in the direction of the city centre) leading to the main underground concourse. A direct link is being constructed from the platform level of the North/South Line to the central underground concourse and the platforms of the East Line. Ground conditions The soil profile at the site is different from the characteristic Amsterdam soil profile. Station Island is an artificial island that was built at the end of the nineteenth century for the construction of Amsterdam CS railway station for Dutch Railways. The island was created by filing in a channel area in the River IJ with sand. At the Station Island location the first Amsterdam underground sand layer is completely missing and the second sand layer is only partially present. The subsoil can be classified as poor. Boundary conditions The design of the underground station at Amsterdam’s Central Station (CS) was largely determined by local environmental constraints. The underground station is being built in front of, behind and also underneath the historic central railway station. Damage to the listed station building and delays to the different passengers and existing traffic flows are not acceptable. A further complication in the design was the soft and highly variable subsoil. Building an underground railway station on such a location can be considered as one of the most challenging constructions of the North-South line. Choice of software For the many unique, project-specific questions there are no existing regulations. This requires a multi-purpose software solution. Due to the high developed graphical output and the many modules we were able to solve a large scale of technical and geotechnical problems by using ESA-Prima Win in combination with M-Sheet and M-Foundation. Short description of the technical challenges Many phases during the building process are characteristic for this project. These phases have a major influence on the applied building method. A distinction can be made between the following parts with their own building phase: • The deep part with diaphragm walls, bored piles and jet grout struts. The deck of the roof will be build in parts and will be in use when the pit is excavated. The deep part will lead the passengers to the North/South Line platform with a connection to the immersed tunnel under the Central Station; • The middle deep part with diaphragm walls, driven piles and underwater concrete. The middle deep part connects the NorthSouth line with the existing East Line; • The entrances from the central underground concourse to ground level. The following parts are specially mentioned Diaphragm walls The permanent diaphragm walls are calculated with MSheet. Because of unequal excavations the reaction forces will be redistributed. This redistribution is determined with ESA-Prima Win and after this corrected in MSheet. After excavation a secondary cast inner wall will be made. This compound wall has a complex geometry and is calculated with 3D-Shell. Jet Grout Strut Stresses in the diaphragm walls will be reduced by applying a horizontal jet grout strut which is placed before excavation. During excavation normal forces and curvature due to swelling groundlayers will occur. This complex situation is investigated with a 3D Shell model including non-linear spring supports. Bored piles / steel concrete columns Before excavation the roof structure is made. This structure will be supported by 20 m long steel concrete columns placed in 40 m long bored piles with a diameter of 1200 mm. The bearing capacity is determined by MFoundation. The structural behavior is determined by ESA-Prima Win and includes non-linear soil behavior and second order effect. Other structural parts The walls, floors are all calculated with ESA-Prima Win using different kind of modules. Points for emphasis It is important to keep complex 3D-models simple and more controllable. Clear agreements have been made concerning the influence of several construction components. Where necessary, calculations have been completed with the geotechnical programs of the MSerie. This ensures an optimum interaction of the possibilities of constructive and geotechnical software. Used modules • MSheet, MFoundation • 3D Shell • 2D Plate and 2D Wall • 2D and 3D Frame • Physical non-linear conditions • Second order and stability frame • Construction stages
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