A novel ground treatment technique

microbial-induced calcite precipitation(MICP)

has recently emerged in geotechnical engineering

which utilizes the calcite precipitation to bind loose particles together; and therefore

the mechanical properties of sand can be enhanced. The objective of this study is to investigate the effect of chemical treatment on the strength of bio-cemented sand. Sporosarcina pasteurii is used to induce calcite precipitation

and all the specimens are prepared by injecting a single concentration or multiple different concentrations of chemical solutions. In this study

0.5 and 1.0 mol urea-calcium chloride solutions are used for the former chemical treatment

while for the latter one

0.5 mol urea-calcium chloride solution is firstly injected; and subsequently

1.0 mol urea-calcium chloride solution is utilized. Based on the experiment

the strength

failure modes and calcite content are analyzed. From the experimental results

it can be found that chemical treatment has significant influence on the unconfined compressive strength of bio-cemented sand soil

but no pronounced effect can be seen in the failure modes and calcite content. Injecting multiple different concentrations of chemical solutions can be beneficial to obtain relative high compressive strength by using less treatment times. Finally

the mechanism analysis corresponding to the effect of chemical treatment on the strength of bio-cemented soil is further conducted.