\r徐宏殷^{1, 2}，练继建^{1, 2}，闫 玥^{1, 2}

AuthorsHTML:\r徐宏殷^{1, 2}，练继建^{1, 2}，闫 玥^{1, 2}

AuthorsListE:\rXu Hongyin^{1, 2}，Lian Jijian^{1, 2}，Yan Yue^{1, 2}

AuthorsHTMLE:\rXu Hongyin^{1, 2}，Lian Jijian^{1, 2}，Yan Yue^{1, 2}

Unit:\r1. 天津大学水利工程仿真与安全国家重点实验室，天津 300350；
2. 天津大学建筑工程学院，天津 300350


Unit_EngLish:\r1. State Key Laboratory of Hydraulic Engineering Simulation and Safety，Tianjin University，Tianjin 300350，China；
2. School of Civil Engineering，Tianjin University，Tianjin 300350，China

Abstract_Chinese:\r为了优选MICP(microbial induced carbonate precipitation)固化砂土过程中的试验因素，采用中心注浆法耦合6个试验因素，以圆形硅质砂为试验材料，根据正交试验的设计原则进行了25种工况的MICP砂柱固化试验．检测了砂柱固化过程中反应前后Ca²⁺浓度变化和固化后砂柱各部位的CaCO₃晶体含量，并采用SEM观测了砂柱内部CaCO₃晶体的微观形态．通过分析各个试验因素对Ca²⁺利用率的影响，发现影响Ca²⁺利用率的主要因素有菌液浓度、胶结液浓度和矿化反应时间，且菌液浓度越高，胶结液浓度越低，反应时间越长，Ca²⁺利用率越高．菌液静置过程中存在细菌下沉现象，从而影响CaCO₃晶体的生成位置．固化砂柱内部CaCO₃晶体分布的研究结果表明，矿化生成的CaCO₃会随着砂土中的水流迁徙，浆液的流速越大，砂柱内部晶体的平均含量越高，且分布越均匀．SEM的观测结果显示，固化砂柱内部CaCO₃晶体以方解石为主，但胶结液浓度会影响晶体的尺寸大小．当胶结液浓度高于750mmol/L时，CaCO₃晶体呈现堆叠式发展．当菌液浓度较高并且胶结液静置时间较短时，会出现球霰石的晶体形态．MICP固化砂土的强度随CaCO₃含量的增加而升高，但同时会受到晶体的分布以及大小等因素的影响．MICP固化砂土试验因素的优选结果为：菌液的OD₆₀₀值0.5～1.0，菌液静置时间3h，胶结液浓度不高于500mmol/L，浆液的流速与传输距离相关，胶结液的最优静置时间为使Ca²⁺完全消耗．

Abstract_English:\rTo optimize the test factors in the process of solidifying sand through the microbial induced carbonate precipitation(MICP)method，25sand column tests，which used round siliceous sands as the test material，were conducted on the basis of the orthogonal design of the central grouting method with 6 test factors that were coupled．The Ca²⁺ concentrations before and after the reaction in the MICP process were detected，and the CaCO₃ crystal contents in different parts of the solidified sand columns were measured．Moreover，the microstructure of the crystals was observed through the scanning electron microscopy(SEM)method．The analysis of the influence of the test factors on Ca²⁺ utilization showed that the major factors affecting Ca²⁺ utilization were the concentration of the bacterial suspension，concentration of the cementing solution，and reaction time．In addition，high concentration of the bacterial suspension，low concentration of the cementing solution and long reaction time result in high Ca²⁺ utilization．Bacterial cells sink during the retention time of the bacterial suspension，which affects the formation position of CaCO₃ crystals．CaCO₃ produced in the MICP process migrates with the flow in sands，affecting the distribution of crystals in the sand columns．A high flow rate of the solutions can result in a high average CaCO₃ content and a uniform CaCO₃ distribution．The SEM images illustrate that the CaCO₃ crystals in the solidified sand were mainly calcite and the concentration of the cementing solution can affect the crystal size．When the concentration of the cementing solution was higher than 750 mmol/L，the crystals showed stacking-type structures．Moreover，vaterite were detected in the test cases with high bacterial concentration and short retention time of the cementing solution．The strength of the MICP solidified sand increases with the increase in the CaCO₃ content；however，it is also influenced by other factors，such as the distribution and size of the crystals．The optimization results of the six test factors are as follows：the OD₆₀₀ value of the bacterial suspension is 0.5—1.0，the retention time of the bacterial suspension is 3 h，the concentration of the cementing solution is lower than 500 mmol/L，the flow rate of the solutions is related to the transport distance，and the retention time of the cementing solution ensures that Ca²⁺ is completely consumed and utilized．

Keyword_Chinese:MICP；砂土固化；CaCO3晶体；试验因素优选

Keywords_English:microbial induced carbonate precipitation(MICP)；sand solidification；CaCO3 crystal；test factors optimization


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