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【目的】确定微生物诱导碳酸钙沉积(MICP)技术注浆固化吹填粉土的强度效果,明确其微观控制因素与固土作用机理,为微生物固土技术应用于处理吹填粉土提供理论参考。【方法】通过不同注浆轮次微生物注浆固化吹填粉土,采用无侧限抗压试验、X射线衍射分析、扫描电镜分析、压汞分析以及化学分析等方法,比较微生物注浆固化处理吹填粉土的强度、矿物成分、胶结CaCO_3含量、土体微观形貌和土体孔径分布等差异。【结果】对吹填粉土先后恒压注入A600=1.2的巴氏芽孢杆菌和0.1 mol/L的CaCl_2与尿素胶结溶液1~6轮后,其无侧限抗压强度较未处理土分别提高26.8%、33.0%、36.4%、39.6%、59.8%、61.8%,强度随注浆轮次的增加而增加;微生物固化吹填粉土中的主要胶结物为方解石型CaCO_3,其在土体内部起到胶结土颗粒与填充孔隙两方面作用,微生物注浆固化粉土强度随CaCO_3含量增加而增加并存在敏感阈值,当固化粉土中的CaCO_3含量超过阈值时,固化效果会显著提升,不同粉土的阈值存在差异;微生物注浆加固改变了吹填粉土的孔隙分布,直径10~300μm的孔隙显著减少,对10μm以下细小孔隙影响不大。【结论】采用微生物注浆方式固化吹填粉土是有效的。微生物注浆固化粉土的强度形成受其微观胶结结构与CaCO_3含量影响,吹填粉土的孔隙尺寸能够与巴氏芽孢杆菌的菌体尺寸相容,微生物注浆会显著减少吹填粉土中10μm以上的孔隙。
【Objective】 The purpose of this study was to determine the strength effect of grouting silt-infiltrated silt by micro-organism-induced calcium carbonate deposition (MICP) technology, to clarify the micro-control factors and soil-fixing mechanism and to provide a theoretical reference for the application of microbial solid- . 【Method】 The grouting silt was filled by different grouting rounds, the unconfined compressive test, X-ray diffraction analysis, scanning electron microscopy analysis, mercury intrusion analysis and chemical analysis were used to compare the effect of grouting and solidification The strength, mineral composition, content of cemented CaCO_3, microscopic morphology of soil and distribution of pore size of soil are different. 【Result】 The results showed that the unconfined compressive strength of poplar silt was higher than that of untreated soil after one to six cycles of constant pressure injection of Bacillus subtilis A600 = 1.2 and 0.1 mol / L CaCl 2 and urea cement solution respectively 26.8%, 33.0%, 36.4%, 39.6%, 59.8% and 61.8% respectively. The strength increased with the increase of grouting rounds. The main cement in the microbial solidified aerated silt was calcite CaCO 3, Plays the role of cemented soil particles and filled pores. The strength of the grouting solidified silt soil increases with the increase of CaCO 3 content and has the sensitive threshold. When the content of CaCO 3 in the solidified silt exceeds the threshold, the curing effect will increase significantly. The threshold of soil is different. The micro-grouting reinforcement changes the pore distribution of aerated silt, and the diameter of pores with diameter of 10 ~ 300μm decreases significantly, which has little effect on fine pores below 10μm. 【Conclusion】 It is effective to solidify aerated silt by microbial injection. The strength formation of micro-grouting solidified silt is influenced by its micro-cementation structure and CaCO 3 content. The pore size of aerated silt can be compatible with the cell size of Bacillus subtilis, and microbiological grouting can significantly reduce Pores of 10 μm or more.