Triaxial Compression Behavior and Damage Model of EICP-Cemented Calcareous Sand

The enzyme-induced calcium carbonate precipitation (EICP) technique was utilized to cement calcareous sand. The mechanical properties of EICP-cemented calcareous sand at various cementation degree were investigated using consolidated drained triaxial compression tests. A statistical damage constitutive model tailored for EICP-cemented calcareous sand was also developed based on damage mechanics theory. The findings are as follows: (1) The EICP technique significantly enhances the cementation of calcareous sand. As the number of grouting operations increases, the peak deviator stress of the cemented material gradually increases, with the maximum enhancement approaching 2.5 times. Moreover, during the stress decay phase following the peak stress, the decay rate of the cemented sand accelerates, displaying a more pronounced brittle characteristic. (2) With the increased calcium carbonate content, the peak eccentric stress of the cemented body increases significantly, and there is an obvious nonlinear exponential correlation between them. (3) The statistical damage constitutive model, formulated based on Lemaitre's strain equivalence principle combined with a log-normal distribution and the Drucker-Prager strength criterion, accurately predicts the stress-strain curves, effectively simulating the complete stress-strain evolution of EICP-cemented sand under different numbers of grouting operations and varied confining pressure conditions. (4) At higher cementation levels or lower confining pressures, the internal damage process of the EICP-cemented calcareous sand specimens intensifies, indicated by the rapid increase of the damage variable D with axial strain. The research findings can provide a crucial theoretical foundation for the application of EICP technology in the treatment of island reef or roadbed foundations, aiding in the analysis and prediction of the mechanical properties of EICP-cemented calcareous sands.