Performance of reinforced soil wall supported by stone columns

A 10 m high reinforced soil (RS) wall has been designed to retain an access road and also the building platform for a mixed development located over a valley terrain. Within the lower part of the valley where the wall is located, the unfavourable ground conditions consisting of approximately 12 m thick soft compressible alluvial deposits overlying a stiff granitic residual formation was revealed during the subsurface investigation. In order to support the high wall vertically and laterally stone columns were adopted for ground treatment as an economic solution. This paper demonstrates the design aspects of the stone column support as a composite treatment for unfavourable ground conditions, the construction QA/QC measures and the verification of the performance using a comprehensive instrumentation scheme. From the instrumentation results the inclinometer and extensometer installed at the edge of the wall show minor lateral squeezing and settlement of the subsoil within the influence depth of the RS wall. However the deformation of the wall as a result of the lateral and settlement movements of the supporting ground is satisfactory and indicates the effectiveness and economy of this proposed solution.