微生物产气降饱和度法处理既有建构筑物下可液化地基的机制研究

Due to the limitations of construction standards, construction level and economic condition, the seismic performance of some existing structures in China is generally insufficient, and it needs urgent reinforcement to improve its safety. In order to break through difficulties of the conventional liquefaction treatment technologies to treatment liquefiable foundation under existing structures, this study aims at developing a desaturation method by microbial gas to treat the liquefiable foundation under existing structures. By combining laboratory tests and theory analysis, soil microbial for the desaturation to liquefaction mitigation is selected and the influencing factors on the performance of microbial gas production is studied. The stability of microbial bubbles in the soil and the indicators and evaluation methods of microbial gas reduced saturation state is researched. A method of saturation control for liquefiable ground treated by microbial gas based on seismic performance is established. The influence of microbial bubbles intervention on the foundation deformation under existing structures foundation is revealed, and a synergistic control method is established for both the control of foundation deformation of existing structures and the microbial gas induced desaturation based on seismic performance. The research results will provide a theoretical basis for the practice of microbial gas induced desaturation to treat liquefiable foundation under existing structures, which will improve the seismic performance and safety of existing structures. It is expected that the research results contribute to the exploration of low-carbon mode and sustainable development in the process of urbanization.

受建设时标准规范、施工水平及经济条件等限制，我国部分既有建构筑物抗震性能不足，亟待加固以提高其安全性。为突破传统地基处理技术无法处治既有建构筑物下可液化地基的工程困境，本项目采用室内试验和理论分析相结合的技术路线，对微生物产气降饱和度法处理既有建构筑物下可液化地基的关键科学问题开展研究。遴选适用于可液化地基降饱和度的微生物菌种并配制其培养基，分析微生物产气性能的影响因素；阐明微生物气泡在土体中的稳定性特征，提出土体中微生物气降饱和状态的表征指标和评价方法，并基于抗震性能提出微生物气处理可液化地基的饱和度控制方法；同时揭示微生物气泡介入对既有建构筑物地基变形的影响，在此基础上，构建既有建构筑物地基变形与基于抗震性能的微生物气降饱和度的协同控制方法。研究成果可为微生物气泡降饱和度法处理既有建构物下可液化地基的工程实践提供理论依据，为探索城市化进程中的低碳化模式与可持续发展做出贡献。

受建设时标准规范、施工水平及经济条件等限制，我国部分既有建构筑物抗震性能不足，亟待加固以提高其安全性。为突破传统地基处理技术无法处治既有建构筑物下可液化地基的工程困境，本项目采用室内试验和理论分析相结合的方法，对微生物产气降饱和度法处理既有建构筑物下可液化地基的关键科学问题开展研究。主要研究成果包括：1）采用室内试验验证施氏假单胞菌的反硝化能力，通过室温状态下砂土的降饱和试验，研究温度、pH、微生物浓度、氮源浓度、表面活性剂种类、表面活性剂掺量、土类这六个影响因素对产气性能特性（产气量、产气速率、停滞时间、产气时间）的影响，提出土体饱和度降低程度的控制指标；2）采用室内试验验证静水条件、向上渗流条件、向下渗流条件与震动荷载作用下微生物气泡在土体孔隙中的稳定性，研究在上述几种条件下微生物气在土体孔隙中的滞留量随时间、水力梯度和循环次数的变化趋势，并确定微生物气泡稳定性的影响因素和相关机理；3）基于振动台模型试验，采用预振动技术测量剪切波速，建立微生物产气过程中的饱和度和剪切波速的定量关系，并建立试样饱和度和电阻率的定量关系，提出基于土样剪切波速或电阻率的降饱和状态评价方法；4）通过室内振动台模型试验，分析孔压比随饱和度、相对密实度和地震加速度的变化规律，提出以平均孔压比和饱和度为参数的模型地基体应变预测经验公式。通过静三轴和动三轴试验研究饱和度对松散砂土静态液化和动态液化特性的影响，提出处理可液化砂土的临界饱和度确定方法。基于两相流模型的降饱和土中水-气两相流体的运移规律。5）基于既有建构筑物下微生物气降饱和地基的振动台模型试验，揭示既有建构筑物基础下地基的位移机制，明确微生物气的介入对既有建构筑物地基变形的影响，构建既有建筑下地基变形与基于抗震性能的微生物气降饱和度的协同控制方法。研究成果可为微生物气泡降饱和度法处理既有建构物下可液化地基的工程实践提供理论依据，为探索城市化进程中的低碳化模式与可持续发展做出贡献。