Investigation of desiccation cracking of earthen site soils treated by enzyme-induced calcium carbonate precipitation (EICP)

The infiltration of groundwater and surface water is critical for the development of desiccation cracking of earthen site soils. It potentially leads to changes in the microscopic structures of pore water networks, posing a threat to the stability of earthen site soils. In this study, the effects of cementation solution concentrations on water holding capacity of earthen site soils and microscopic characteristics are investigated using the method of enzyme-induced calcium carbonate precipitation (EICP), volumetric shrinkage and suction tests under wetting-drying loadings, and microscopic tests. The microscopic characteristics regarding pore structures are used to interpret the mechanism of desiccation cracking of EICP-treated earthen site soils from the microscopic perspective. The results show that the rate of drying shrinkage and sensitivity to drying and wetting conditions of earthen site soils are notably reduced by the method of EICP. The volumetric shrinkage curves appear three-stage evolving trends. The microscopic tests show that the treated earthen site soils feature bimodal distributions of pore structures. With this regard, the uniformities of pores are significantly improved, for which large and medium pores of untreated soils are filled by the method of EICP. Small and micro pores are compressed, which reduces the potential connectivity of pores inside earthen site soils. The research outcomes can provide fundamental knowledge for improving desiccation cracking of earthen site soils by the method of EICP.