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Title: Design and construction of a prestressed diaphragm wall with burtresses

Author(s): Molins Borrel, C.; Ledesma Villalba, A.; Casals Bohigas, R.; Jaén González, C.

Publication: ACHE

Volume: 59

Issue: 247

Appears on pages(s): 45 - 54

Keywords: Diaphragm wall, prestressed concrete, existing tunnels, existing structures interaction, field monitoring.


Date: 1/1/2008

This paper describes the design, construction and early performance of a retaining structure close to a subway tunnel in Barcelona. The excavation, about 16 m deep, was carried out in 2001 during the construction of a new Hospital and involved a rectangular area with the longer side (170 m) almost parallel to the tunnel. The design had to fulfil two requirements: First the influence of the excavation on the existing tunnel should be minimized and secondly the new hospital had to be isolated from the vibrations of the subway due to the high sensitivity of the medical instruments. In order to achieve that, the designed retaining wall was independent of the main building and the movements during the excavation stages had to be controlled. In addition, the use of sub-horizontal anchors was not allowed by the Metro Administration and therefore the wall comprised a line of T shaped panels linked to shorter intermediate panels excavated using a Hydromill. The stability of the wall and bending resistance were provided by the buttressing effect of the forward facing T and the compression in the panels and anchoring force provided by post tensioning anchors drilled into the underlying bedrock through ducts installed in the rear section of the T panels. The wall was designed using a ?beam-spring? model with ground parameters derived from in situ tests and the interaction between the excavation and the tunnel was carried out using a plane strain finite element analysis imposing the wall displacements on the section. The monitoring of the wall and the tunnel confirmed that the influence of the work on the neighbour tunnel was almost negligible.

ACI International Partner, ACHE Spain, International Partner Access

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