Comparison of bioaugmentation and biostimulation approaches for biocementation in soil column experiments

Microbially induced carbonate precipitation (MICP) is an innovative soil improvement technology. In the past, the most widely used method was bioaugmentation. Recently, biostimulation has attracted the attention from many researchers. There may be differences in the treatment effect when different methods are used. In this study, the soil improvement effects of these two methods were compared. In the experiment, two different nutrients (yeast extract and beef extract) were used and the initial urease activity between bioaugmentation and biostimulation was controlled at a close level. The results showed that biostimulation was a more environmentally friendly, costeffective and gentle method. Biostimulation can achieve more sustained mineralization. The samples treated with biostimulation showed higher calcium carbonate precipitation content (CCP), shear wave velocity (Vs) and unconfined compressive strength (UCS) for the same cementation treatment cycle. Yeast extract was found to be more effective than beef extract in both bioaugmentation and biostimulation for the same cementation treatment cycle. However, the use of bioaugmentation and beef extract can result in higher soil strength for the same calcium carbonate precipitation content. This is related to the difference in CaCO3 crystal precipitation pattern using different treatment methods and nutrients. This study is expected to provide a basis for the selection of MICP treatment methods.