A comparative assessment of biogrouting versus electro-biogrouting for the treatment of fine-grained soils

This paper presents a comparative experimental study carried out on artificial sandy clay soil mixtures to assess the effectiveness of conventional biogrouting against that of electro-biogrouting in a one- dimensional small scale laboratory experiment, using Sporosarcina pasteurii strain. The comparison was done in terms of unconfined compressive strength (UCS) gain when using respectively the two techniques, as well as calcite precipitation attested by X-Ray Diffraction (XRD) analysis. Three different sand-kaolin mixes were prepared, with increasing kaolin contents namely 30%, 40% and 50%. The experimental results indicate that electrokinetic injection increased the UCS of the clay soil up to 90% and 187% at 7- and 14- days curing time respectively, depending on the soil type. In terms of per cent increase in UCS compared to the UCS of the untreated soil mixes, UCS gain between electrobiogrouting and conventional biogrouting differed by 23%-58% with those observed in electrobiogrouting being consistently the highest.