The Investigation of the Mechanical Properties of EICP-Treated Sand Specimens Prepared by a Double-Reservoir Injection System for Uniform Precipitation of Carbonate via Triaxial Tests

Abstract

Abstract The injection condition of enzymatic-induced carbonate precipitation (EICP) grouting for uniform precipitation and the mechanical properties of EICP-treated soil specimens were investigated in this study. Urease derived from yellow soybeans was used as the catalyst for the precipitation of the carbonate instead of the expensive purified urease commonly used. The uniformity of the calcium carbonate distribution was investigated by measuring the calcium carbonate content at various locations within the EICP-treated soil specimens through the soil column injection tests. The results showed that the uniformity of the calcium carbonate distribution depends on the reservoir system for the storage of the injection solutions and the injection volume that is associated with the colloidal transport of urease. Based on the proposed injection method, the EICP-treated soil specimens were prepared for two soil types and a series of consolidated undrained triaxial compression tests were conducted to investigate the mechanical properties. It was confirmed that the undrained shear behavior of the EICP-treated sand specimens shows more softening behavior. In addition, the use of a high molarity urea-CaCl2 solution resulted in pronounced reinforcing effects on the strength, which included both the peak and residual strength and the stiffness. The effects of the confining pressure and the soil types on the strength and stiffness were also investigated.