可液化砂土微生物处置试验

An experimental study of microorganism’s treatment on liquefiable sands

摘要:

为科学评价实验室试样尺度下MICP对可液化砂土的加固效果，采用监测营养盐注浆过程中压力变化和铵根离子量变化方法，比较试样尺度放大和注浆流速变化条件下可液化砂土的刚度和渗透性差异.试验结果表明：以巴氏芽孢八叠球菌为菌液、乙酸钙和尿素为营养盐，采用间歇式注浆方式制备固化砂土试样，注浆过程中试样内部压力变化和铵根离子变化能够有效表征可液化砂土的MICP加固效果；试样尺度放大时，依据面积比设计注浆流速，灌浆压力显著降低，试样成矿均匀性显著提高.监测试样压力变化和铵根离子变化，是研究可液化砂土微生物处置效果的简单和非破坏性试验方法.MICP应用实践中，随着试样尺度的放大，需要兼顾刚度、成矿均匀性和注浆流速之间的平衡.

Abstract:

To evaluate the sand consolidation effect of MICP under the condition of the laboratory, the stiffness and permeability of the liquefied sand samples of different size under different grouting flow velocity were analyzed by monitoring the change of internal pressure and the amount of ammonium ion in the process of the grouting of nutrient salt. Sporosarcina pasteurii was selected to produce bacteria liquid, with nutritive salts, such as calcium acetate and urea. The intermittent grouting method was applied to produce solidified sand samples. Results show that the MICP modification effect can be effectively characterized with the variation of internal pressure and the concentration of ammonium during grouting. When grouting velocity is designed according to the area ratio, the grouting pressure is significantly lower down and mineralization uniformity is significantly improved along with the sample size increasing. Monitoring the change of the pressure and the amount of ammonium ion is a simple and non-destructive method for the study of the effect of the microbial treatment of liquefied sand soil. In the application of MICP, the design of grouting should consider both rigidity and mineralization uniformity when the sample size is enlarged.