微生物注浆加固粉土模型试验研究

Experimental Study on Silt Model Reinforced by Microbial Grouting

摘要: 为探索微生物注浆技术的大规模应用，文章进行了基于微生物诱导碳酸钙沉淀(MICP)技术的粉土固化大尺寸模型试验。试验以黄河中下游的典型粉土为加固对象，通过蠕动泵以低压将微生物菌液和营养盐注入粉土中。研究分析了在不同注浆量条件下，粉土表层的扩散半径、注浆管道周围的凸起高度及其半径之间的关系，并观察了粉土加固后沿注浆管pH值的变化；通过直剪试验和静三轴固结不排水试验，分析了加固粉土的强度和变形特性；同时，借助盐酸溶解试验阐述了碳酸钙生成与强度变化之间的关系。试验结果表明，微生物扩散效果并不会随着注浆量的增加而持续提升。此外，经过MICP处理后的土体pH值略有上升，这表明碳酸盐的有效沉淀。随着注浆量的增加，土样中的碳酸钙沉淀量增长，进一步促进了内摩擦角和粘聚力的提高，增强了土样的抗剪强度。同时，无侧限抗压强度也因碳酸钙生成量的增加而显著提升。当注浆量达到3200 ml时，处理后的土体无侧限强度相比未进行MICP处理的土体提升了86.8%。在低围压(100 kPa)条件下，素土表现出应变软化特性，而在高围压(200 kPa和300 kPa)条件下则表现为应变硬化。在相同围压条件下，随着注浆量的增加，加固土在弹性阶段的强度提升速度更快，峰值强度显著增强，同时峰值点的轴向应变也显著增大。本研究成果可为生物注浆加固粉土的应用提供一定的参考价值。

Abstract: In order to explore the large-scale application of microbial grouting technology, this paper conducted a large-scale model test of silt solidification based on Microbially Induced Carbonate Precipitation (MICP) technology. In the experiment, the typical silt in the middle and lower reaches of the Yellow River was used as the reinforcement object, and the microbial liquid and nutrients were injected into the silt at low pressure through the peristaltic pump. The relationship between the diffusion radius of the silt surface, the height of the bulge around the grouting pipe, and its radius under different grouting amounts was studied and analyzed, and the change of pH value along the grouting pipe after silt reinforcement was observed. The strength and deformation characteristics of the reinforced silt were analyzed using a direct shear test and a static triaxial consolidated undrained test. At the same time, the relationship between calcium carbonate formation and strength change was described by the hydrochloric acid dissolution test. The test results show that the microbial diffusion effect will not continue to increase with the increase of grouting amount. In addition, the pH value of the soil after MICP treatment increased slightly, indicating the effective precipitation of carbonate. With the increase of grouting amount, the amount of calcium carbonate precipitation in soil samples increases, which further promotes the improvement of internal friction angle and cohesion and enhances the shear strength of soil samples. At the same time, the unconfined compressive strength is also significantly improved due to the increase in calcium carbonate production. When the grouting amount reaches 3200 ml, the unconfined strength of the treated soil is 86.8 % higher than that of the soil without MICP treatment. Under low confining pressure (100 kPa), the plain soil exhibits strain-softening characteristics, while it exhibits strain-hardening under high confining pressure (200 kPa and 300 kPa). Under the same confining pressure, with the increase of grouting amount, the strength of reinforced soil increases faster in the elastic stage, the peak strength increases significantly, and the axial strain at the peak point also increases significantly. The research results can provide some reference value for the application of biological grouting to reinforce silt.