微生物灌浆加固地基的多物理场耦合数值模拟研究

Multiphysics coupling numerical simulation study of microbial grouting for foundation reinforcement

微生物灌浆加固地基是一种利用微生物诱导碳酸钙沉淀的新技术,具有加固效果明显、扰动小、环保等优势,是当前地基加固技术的前沿问题。微生物灌浆效果与地基中生成的碳酸钙均匀性及含量有密切相关。通过建立灌浆过程中的多孔介质渗流、溶质运移传输和微生物生化反应一维耦合模型,加入微生物初始分布和微生物活性随时间衰减模型,对微生物灌浆生成碳酸钙分布进行了模拟,并与5 m砂柱的试验结果进行对比验证。分析微生物初始分布以及不同灌浆参数(灌浆速度,胶结液浓度和灌浆次数)对灌浆效果的影响,给出了多因素影响下的最优灌浆方式。结果表明微生物初始分布、灌浆速度和次数均对最终碳酸钙量和分布影响很大,胶结液浓度对最终碳酸钙量影响最小,适中灌浆速度和分步灌浆能提高碳酸钙的均匀性。研究显示菌液和胶结液反向分步灌浆,胶结液浓度为1~1.5 mol/L,采用较高的灌浆速度的灌浆方式,能有效减少碳酸钙在入口处的堵塞,提高灌浆效果。

Biogrout is a new ground improving bio-geotechnology which utilizes the microbial induced calcite precipitation(MICP)technology.It is a promising ground improving technology because of its high efficiency,low disturbing and environmental friendly.The biogrout efficiency is closely related to the precipitated calcite uniformity and amount in the ground.A one dimensional fluid-flow,solute transport and bio-chemical reactive model was proposed to simulate the multicomponent interactions,which considered the biomass initial distribution and the activity reduction with time of microbials.The model simulated the distribution of calcite precipitated by biogrout and was verified by an experiment which was carried out in a 5 m soil column.The numerical results were agreed well with the experimental data.Then the initial biomass distribution and injection factors(injection rate,chemical concentrations and the injection method)were studied to analyze the MICP effect.The results of this study indicate that the biomass initial distribution,the injection velocity and the number of times have great impact on the calcite precipitation,while the solution concentrations has least impact on the calcite precipitation.The biomass distribution mode,medium injection velocity and multi steps injection can improve the uniformity of calcite in the column.The best injection method is pulsed injection with opposite injection direction of bacteria and cementation solution,1-1.5 mol/L solution concentration,and relative higher injection rate,which can reduce the clog in the entrance of the column.