Field implementation to resist coastal erosion of sandy slope by eco-friendly methods

Coastal erosion is a global issue that not only compresses land space but also undermines offshore structures. In this study, two eco-friendly technologies (microbially and enzyme induced calcium carbonate precipitation) were implemented at a sandy slope field site to enhance erosion resistance. Improvement of the treated sandy slope against erosion was assessed by penetration resistance, calcium carbonate content, cone penetration testing (CPT) results, terrain data and microscopic morphology. Results indicated that the penetration resistance and calcium carbonate content of treated slopes increased first and then decreased over time because of the gradual formation of calcium carbonate and the erosion caused by the marine environment. Calcium carbonate content and penetration resistance presents an obvious linear relationship. The existence of the superficial cemented crust layer increased the water retention capacity of the sand in the atmosphere region. The calcium carbonate content and CPT results in the tidal region shows the characteristics of layered cement. The spherical calcium carbonate cementation improves the roughness and integrity of the terrain, enhances the particle size of the sand, gradually changing the topography from pre-treatment dynamic erosion to depositional patterns. The treated slope still maintained a certain penetration resistance and calcium carbonate content for 60 days until being eroded by the wind in the atmosphere region. However, the effective protection duration in the tidal zone which encounters wind, wave, tide and reflow was about 24 days, and would thus need to be reinforced periodically over time to obtain long-term protection.