Investigation of field instrumentation in a preloading project Available to Purchase

Preloading with prefabricated vertical drains (PVDs) is one of the most successful methods for improvement of soft soils settlement. A preloading project is described in the southwest of Iran near the Persian Gulf, in which well-planned instrumentation was used. The purpose of the project was placement of an 8 m embankment with installation of PVDs to accelerate the consolidation of subsoil for construction of a concrete water tank, 100 m × 150 m with total volume of 100 000 m³. The thickness of soft soil was about 15 m. This paper presents results of soil instrumentation to measure dissipation of excess pore pressure, differentiating settlement in different soil layers and a comparison of the measurements with predicted settlements and consolidation–time variations according to radial consolidation theory, the results of Settle3D analysis and the Asaoka method. In addition, smear zone effects caused by PVD installation are studied and suitable parameters of soil permeability and smear zone are proposed for future projects. The results clarify that if consolidation parameters are selected adequately based on laboratory tests, the maximum settlement and consolidation–time relations are estimated properly both by conventional theoretical solutions and by more detailed solutions such as Settle3D.