As cementing materials

cement and chemical grouts have often been used for soil improvement. However

high energy consumption

high-pollution discharge and high cost restrict their applications. A new soil improvement method

called bio-grouting reinforcement technology

has recently emerged

which is based on microbial induced calcite precipitation by injecting bacteria solution and nutrient into loose sand for the purpose of binding soil particles together and improving its physico-mechanical properties. Laboratory and field experimental studies of bio-grouting treated soils are systematically summarized. The engineering characteristics of bio-treated soils

non-destructive geophysical process monitoring method

and factors influencing the improvement effect are also discussed. The research results show that the bio-grouting process has many advantages such as small disturbance

low grouting pressure

less environmental harm

and remarkable treatment effect on improving the engineering properties of the soil (e.g. strength

stiffness

liquefaction resistance)

which make it a broad engineering application prospect in soil improvement. However

the durability of bio-treated soils and economy of bio-grouting still need discussing and investigating further.