Sand Foreshore Slope Stability and Erosion Mitigation Based on Microbiota and Enzyme Mix-Induced Carbonate Precipitation

To mitigate foreshore erosion, it is necessary to find effective and environmentally friendly interventions to stabilize slopes. In this study, the microbiota and enzyme mix-induced carbonate precipitation (MEMCP) method was proposed to improve foreshore slopes' stability and mitigate erosion. In the tests, the volume ratio of bacterial suspension (BS) and urease solution (US) varied to obtain the optimum condition. The angles of slopes, accumulative soil loss weights, surface strengths, and calcium carbonate (CaCO3) contents were used to evaluate the treating effect. The results showed that the slopes treated with microbially induced carbonate precipitation still experienced a drastic collapse. The slopes treated with enzyme-induced carbonate precipitation had higher stability at the beginning; however, the slopes were still damaged in subsequent tidal cycles. However, with MEMCP treatment, the slopes' stability was significantly improved, especially for the slopes with the volume ratio of BS to US equaling 20:20. The angle of these slopes almost did not change, and a small amount of sand was washed out by tidal cycles. Moreover, these slopes had higher surface strengths and CaCO3 contents. In addition, the increase in CaCO3 content resulted in an exponential increase of surface strength, regardless of volume ratios of BS and US. The MEMCP method applied in this study for foreshore slope stabilization has shown a success. The research lays a solid foundation for the application for foreshore surface erosion mitigation.