Abstract
Reinforcement of calcareous sands based on microbial induced calcium carbonate precipitation (MICP) method has become a hot research topic in recent years. However, the disadvantage of MICP method is that the desired effect of improvement can only be achieved by multiple treatments of the cementing solution. In order to enhance the efficiency of MICP in reinforcing calcareous sands, an appropriate amount of iron ions was added to the cementing solution, followed by solution tests and sand column tests to assess the reinforcement effect through calcium carbonate generation, UCS and permeability coefficient. The results show that iron ions can change the morphology and size of MICP calcium carbonate in the solution test; in the sand column test, when iron ions were added to the cementing solution, the UCS of the sand column could reach up to 2832.63 kPa after five injections, and the UCS of the conventional MICP test group under the same conditions was only 185.5 kPa, and the permeability coefficient was reduced by two orders of magnitude compared with that of untreated sand. Iron ions did not increase the amount of MICP calcium carbonate in the sand column test, but changed the distribution pattern of calcium carbonate, thus increasing the strength and decreasing the permeability coefficient of the sand.