Strength analysis of EICP-solidified shield muck with different particle sizes under low-pH conditions

High water content and residual foaming agents make shield muck difficult to reuse directly, highlighting the importance of improving its solidification effect. The single-phase low pH grouting method possesses the characteristic of retarding the Enzyme-Induced Carbonate Precipitation (EICP) reaction process, constituting a key advantage of this technology. Based on this, strength tests were conducted on EICP-solidified shield muck under low-pH conditions. The study investigated the calcium carbonate content, ultrasonic wave velocity, permeability coefficient, and unconfined compressive strength of the solidified muck under different particle size ranges, foaming agent types, and numbers of solidification cycles. The influence of these factors on the solidification effect was quantified. The results showed that, under the same number of treatments, the unconfined compressive strength of samples with particle sizes in the ranges of 0.5~1 mm and 0.5~2 mm solidified with 0.1% anionic surfactant (AES), and 0.1% nonionic surfactant (APG) was higher than that of samples solidified in deionized water (DW). In contrast, for samples with particle sizes in the range of 1~2 mm, the strength under AES and APG conditions was lower than that under DW. This study compared the effects of multiple factors on the solidification effect of EICP in shield muck, providing practical insights for the application of EICP in shield muck stabilization under low pH conditions.