Comparitive studies on prefabricated vertical drain & stone column on consolidation

Abstract

A comparative study of the consolidation behaviour between stone column and prefabricated vertical drains has been carried out. The objective of this study is to compare the consolidation behavior of stone column and the prefabricated vertical drains (PVD) on the rate and magnitude of settlement through the plots from the equations in the literature and their performance on site. The data has been obtained from the construction of San Tin Drainage Project which was designed by the Civil Engineering and Development Department. The data is presented in the form of plots, numerical values and 2-D sections. The data has been interpreted in relation to the Terzaghi’s 1-D Consolidation Theory, Hansbo’s smear effect theory, as well as using Priebe’s settlement reduction factor for stone column. A graphical relationship on the consolidation rate is drawn between the PVD and stone column. It is concluded that, the external driving force of installation of the two ground treatment methods induces addition settlement. Also, the larger disturbance during installation of stone column results in a larger discrepancy of the settlement magnitude and rate than that in PVD. The Ch value, back calculated from the monitoring data, of CHD1400R treated by PVD lies between 1.5-2.0m^2/year while that of stone column of Zone A of pumping station lies in a range of 0.27 to 1.3m^2/year.