微生物灌浆技术加固钙质砂的实验研究
Experimental Study of the Cementation of Coral Sand by Biogrouting

微生物诱导碳酸钙加固技术(MICP)与传统化学灌浆加固技术相比，能有效提高砂土的强度、渗透性及抗侵蚀性能等，且微生物灌浆材料为溶液或悬浊液，与传统胶凝材料相比，具有黏性低、流动性好、反应速率可调控、环境污染少等优势。向砂土柱中灌注菌液以及胶结溶液(尿素和氯化钙混合溶液)，通过四轮注浆实现对砂土柱的加固，基于无侧限抗压强度实验，分析砂土颗粒级配、营养液浓度对于砂土柱加固效果的影响。并且结合电镜扫描探究微生物灌浆加固技术的微观机理，实验结果表明：砂颗粒之间有明显的碳酸钙生成，生成的碳酸钙呈现出膜结构和颗粒的形态，将砂土颗粒黏结并填充起来，形成一个更加致密整体，从而提高砂土柱抗渗性和抗压性，同时适宜的浓度和颗粒大小对加固起到了明显的促进作用。
Compared with traditional chemical grouting reinforcement technology, microbial induced calcium carbonate reinforcement technology (MICP) can effectively improve the strength, permeability and erosion resistance of sand, and the microbial grouting material is a solution or suspension, and traditional cementitious materials. Compared with the advantages of low viscosity, good fluidity, adjustable reaction rate and less environmental pollution, the bacteria liquid and the cement solution (mixture of urea and calcium chloride) are poured into the sand column, and the sand column is strengthened by four-round grouting. Based on the unconfined compressive strength test, the effects of sand particle size distribution and solution concentration on the reinforcement effect of sand columns are analyzed. Combined with electron microscopy scanning, the microscopic mechanism of microbial grouting reinforcement technology was explored. The experimental results show that there is obvious calcium carbonate formation between the sand particles, and the formed calcium carbonate exhibits the structure of the membrane and the shape of the particles, and the sand particles are bonded and filled. A more compact whole is formed to improve the impermeability and compressive strength of the sand column. At the same time, the appropriate concentration and particle size play a role in promoting reinforcement.