Field Trial of EICP Reinforced Beach Slope against Coastal Erosion

With climate change causing sea level rise globally, as a low-lying island city, Singapore is particularly susceptible to the threat of the sea level rise. The 30% of coastline in Singapore comprises natural areas such as sandy beaches, rocky shorelines, and mangroves; they are vulnerable to the intensifying high tides and large waves. Beach erosion has become an urgent issue for the city to mitigate the overwash effect and stabilize the sand. Conventional measures to prevent coastal erosion include building seawalls or breakwaters, beach nourishment, geotextile wall installation, and planting vegetation. In this study, a new product, eco-cement, which is based on the enzymatic induced carbonate precipitation (EICP), was developed to stabilize the sand slope. Laboratory sand column tests have shown compressive stress strengthening and permeability reduction. A field-scale trial was carried out using the combined spray and injection method to solidify the beach sand. The calcium carbonate crystals effectively bond sand particles and furthermore forming a crust at the surface of sand slope to mitigate the erosion caused by waves. Challenges for the scale-up of EICP from laboratory technique to field application are addressed. Sequential injection and spray strategy is encouraged to achieve the uniformity of the calcium carbonate precipitation within the sand. Sand properties including the compressive strength and microscopic structures were examined to assess the improvement. A subsequent long-term monitoring of the treated sand slope has also shown the effectiveness of the EICP treatment and the increase of erosion resistance.