Experimental study on biological solutions for anchoring earthen heritage sites

In projects with earthen cultural heritage sites, selecting appropriate grouting materials is essential and challenging. This study examines the soil from the Zhouqiao site, with the objective of developing an innovative grouting material. The Enzyme-Induced Calcium Carbonate Precipitation (EICP) technique was utilized to modify soil-fly ash mixed grouting material. Mechanical performance tests and microanalysis were performed under different material ratios, concentrations of cementing solution, and freeze-thaw cycles. The results demonstrate that optimal mechanical performance of the grouting material is achieved with the soil-ash ratio of 1:1, water-cement ratio of 0.52 and concentration of cementing solution of 0.8 mol/L. Multiple freeze–thaw cycles lead to a decrease in compressive and shear strengths, causing a reduction in the internal friction angle by up to 46.42%. Microanalysis indicates that EICP treatment enhances cementation and bridging between particles. These findings provide a scientific foundation for optimizing EICP technology in earthen heritage site anchoring.