Effectiveness of Cross-Walls in Reducing Wall Deflections in Deep Excavations

Synopsis:

Cross-wall is common construction method for protecting structures adjacent to deep excavations. It was initially developed for improving bottom heave stability and limiting displacements in deep excavations using diaphragm walls to act as cross-walls below the final excavation level in soft clay in Norway. Case histories for using cross-walls to reduce the displacements for excavations as deep as 32.5 m deep in soft clay in Taipei are reported. Although these case histories show that cross-walls are very effective in reducing lateral displacements of diaphragm wall, the design methodology has not been fully developed. The key parameters for design and analysis would be the stiffnesses for soils and for the cross-wall panels. Three cross-walls were installed to brace the diaphragm walls prior to excavation for a cross-over tunnel of the Taipei Metro in front of the South Gate of the old Taipei City and has now been a National Heritage.…