Application of casein-combined enzyme-induced carbonate precipitation to mitigate shallow failure in cut slope

The shallow failure of the cut slope above the road mainly affected the road network in Laos, which could be partially or entirely blocking the roads and causing disruption to traffic. This study investigated the application of casein-combined enzyme-induced carbonate precipitation (CCEICP) technique to mitigate shallow failure in cut slopes. A small-scale model treated by spraying the CCEICP solution was exposed to artificial rain to evaluate the applicability and effectiveness of the treatment. In the CCEICP solution, urea and calcium chloride concentration was 1 M. The percentage of casein to the enzyme-induced carbonate precipitation (EICP) solution was 2.3%, and the proportion of urease enzyme to EICP solution was 3 g/L. The investigation focused on (i) rainwater infiltration investigated using a camera and moisture sensors; (ii) unconfined compressive strength (UCS) and thickness of the crust evaluated using a hand penetrometer and calliper, respectively; (iii) subsidence of slope investigated using displacement sensors and (iv) surface erosion investigated by visual observation with the naked eye. The results showed that the treatment produced an impermeable and hard crust with a 7.97-cm thickness with an initial UCS of 1453 kPa that decreased to 307.5 kPa after rainfall exposure. Its retained strength protects the slope surface from erosion. The treatment also created an impermeable layer concentrated near the slope surface, which reduced rainwater infiltration through the surface. Consequently, the treated slope remained stable after exposure to 113 mm/h of rain for approximately 15 h and 39 min. In contrast, the untreated slope collapsed within 11 min and 30 s.