Soft clay improved by deep cement mixing column technique

The ground improvement techniques have advanced at a rapid pace over the last three decades. Deep mixing is one of those techniques that have been widely utilized to improve soft clay soils in terms of their bearing capacity, settlement, and shear strength characteristics. In this technique, rigid treated soil-columns are formed through mixing soft soil with hardening agents such as cement to produce firmer ground with stronger characteristics. Although numerous researches have investigated the bearing capacity of soil improved by deep mixing method at laboratory, the adopted column installation technique was unlike the column installing conditions in field. In the present study, an experimental test setup was established to install deep mixing columns with similar conditions as in situ with regard to drilling and injection via a small-scale laboratory equipment. Furthermore, a finite element analysis was utilized to simulate the experimental test series using three-dimensional finite element software (PLAXIS 3D). The behavior of strip footings supported by partially penetrating and fully penetrating soil–cement columns has been analyzed through a comparison between the results obtained from experimental tests and numerical simulation. Three length/diameter (L/D) ratios of 4, 6, and 8 and three improvement area ratios (Ar) of 13.1%, 19.6%, and 26.2% were considered. The obtained results showed that the ultimate bearing capacity (UBC) and settlement performance of the model footing supported by soft clay soil improved with either partially penetrating or fully penetrating columns have significantly improved with a good agreement between the two cases of experimental testing and numerical study results compared to the case without columns.