ABSTRACT
The first stage in the construction of a typical cut-and-cover metro station structure, invariably, is the installation of the perimeter wall. It either forms an integral part of the permanent structure itself or is treated as an outer temporary cofferdam within which the main structure is constructed. In view of the significant depths to which such a structure is generally required to penetrate below ground, construction of the perimeter wall in the conventional manner in an open cut, would require vast corridors of land outside the perimeter to accommodate the formation of stabilized side slopes. However, in heavily built-up urban environments generally encountered in metro alignments where existing structures can be expected to be closely abutting the works, such a luxury is rarely available. Under such circumstances, the perimeter walls are installed vertically with the least amount of intrusion beyond the perimeter and often using the slurry trench techniques.
