Performance evaluation of a surcharge preloading project based on back-analysis of field monitoring and numerical assessment

Abstract

This study deals with the performance evaluation of the soil improvement using surcharge preloading techniques with prefabricated vertical drains (PVDs) for the Mahshahr oil storage tanks project as a case study. First, the ultimate settlement values were predicted using observational methods, then, to determine the modified preloading design parameters, the involved parameters such as compression index (Cc) and preconsolidation pressure (P c) were back-analyzed by comparing measured data with the numerical simulations. To this end, the numerical simulation was carried out using Settle3D software. The numerical model results indicated that the settlement value using modified parameters obtained from the back-analysis procedure was lower than the calculated settlement based on the assumed parameters in the initial estimation, which can be attributed to the conservative determination of initial geotechnical parameters. Moreover, optimum spacing and depth of PVDs were evaluated, and soil settlement was compared before and after the preloading operation. It was concluded that after preloading, soil settlement approached acceptable settlement values, which indicates the efficiency of this method for large-scale soil improvement projects.