Ultimate bearing capacity of soft soil improved by DCM columns: a comparative review

Abstract

The use of deep cement mixing (DCM) columns for soil stabilization is an economical and reliable ground improvement technique that has been studied extensively. The aim of this article is to review the ultimate bearing capacity (UBC) of soft soils improved by DCM columns in a series of 1 g physical modelling tests. Reliable databases of 35 stabilized tests using end-bearing DCM columns and 42 stabilized tests using floating DCM columns are analyzed. The effects of the influencing parameters of undrained shear strength of the soil (Cus) and DCM columns (Cuc), and the area improvement ratio (α) on the UBC and bearing capacity (Nc = UBC/Cus are discussed. The failure modes of the improved soil have been compared. The review results show that, for end-bearing and floating DCM columns, the role of α and the strength ratio between the columns and soil, respectively, are vital. The effect of the average end-bearing factor for DCM columns (Nc = 15.27) on the UBC was found to be higher than for floating DCM columns (Nc = 8.08). The experimental results were used to develop four computational models to estimate the UBC of stabilized soil improved by end-bearing and floating DCM columns.