Influence of Different Grouting Methods on the Solidification Uniformity of Marine Silt via SICP Technology

Marine silt is characterized by a high content of fine particles and low permeability, which often result in uneven urease diffusion, local enrichment, and significant variations in solidification performance during soybean urease-induced calcium carbonate precipitation (SICP) treatment. To address these issues, this study experimentally investigated both the preparation of marine silt mechanical specimens and the injection uniformity of the SICP technique. A cylindrical transparent acrylic mold together with a matching grouting device was developed to enable the observable and standardized preparation of marine silt specimens. On this basis, a series of experiments were conducted, including measurements of urease distribution under single SICP grouting, unconfined compressive strength (UCS) tests of solidified specimens, and quantification of calcium carbonate production. The effects of injection direction, injection volume, and injection rate on solidification uniformity and mechanical strength were systematically examined. The results show that the grouting direction governs the stratification characteristics of urease within the specimens. Increasing the grouting volume significantly enhances the total urease content and improves its distribution uniformity. The UCS of the solidified specimens was found to be closely related to the uniformity of urease distribution. Among the tested methods, the multi-round alternating injection mode from both the top and bottom produced the best overall strength performance. The maximum UCS reached 93.81 kPa at a grouting volume of 150 mL and a grouting rate of 5 mL/min. This study clarifies how injection parameters can be optimized to improve the solidification uniformity of fine-grained marine sediments and provides technical support and parameter references for the standardized preparation of SICP-solidified soil mechanical specimens.