Mechanical behaviour of EICP-treated calcareous sands: experimental study and constitutive modelling

Enzyme induced carbonate precipitation (EICP) is an effective and promising biocementation technique for soil reinforcement. Calcareous sands exhibit special physical characteristics, including complex particle shapes, angularity, and abundant inner pores, due to their unique biogenesis. The mechanical behaviour of EICP-treated calcareous sands could be influenced by both the cementation level and particle breakage. In this study, triaxial and one-dimensional compression tests were conducted on untreated and EICP-treated calcareous sands with varying cementation levels. Results show that the strength and dilatancy were significantly improved by increasing the carbonate content, resulting in more obvious brittleness in the EICP-treated calcareous sands. Both the bond strength and the yield stress followed exponential relationships with the carbonate content. By introducing bond strength and particle breakage yield stress, a constitutive model was developed within the framework of super-subloading concept. Relationships between the state variables and carbonate content were quantitatively addressed. The simulation results agreed well with the experimental measurements, demonstrating the effectiveness and capability of the proposed model to describe the mechanical features of the calcareous sands treated under various cementation and stress conditions.