Durability of improved sandy soil using the soybean crude urease calcite precipitation (SCU-CP) method

Increasing the soil shear strength is necessary to prepare the soil before construction. Chemical and physical stabilization can increase the soil-bearing capacity. The latest chemical stabilization method is the calcite method. The calcite precipitation method of Soybean Crude Urease Calcite Precipitation (SCU-CP), which utilizes soybeans as a biocatalyst, was used in this study. In previous studies, the improvement in sand parameters after treatment with calcite precipitation has been verified; however, the results varied. Therefore, it is necessary to conduct a durability test to evaluate the resistance strengthened by calcite. In this study, a durability test was conducted using a wet-dry cycle test, which evaluated the shear strength to determine changes in the parameters of shear strength, volume degradation, and sample mass. The soil treated by SCU-CP had a cohesion and an internal friction angle of 37.05 kPa and 14.27°, respectively. The durability test results showed that the cycle progressed, resulting in a decrease in the cohesion and internal friction of 58.68% and an internal friction angle of 70.15%, respectively, after the 5th cycle. In addition, the volume and mass of the treated soil decreased by 13.22%. This study elucidated that the improved soil using SCU-CP has great potential as an alternative soil improvement method; however, the control of wet-dry conditions in real field applications should be considered.