微生物注浆加固砂土地基的抗液化能力研究

发布时间：2018-02-03 12:16

本文关键词： 液化砂土地基加固微生物注浆微生物诱导碳酸钙结晶动力反应微生物传输　出处：《清华大学》2013年硕士论文　论文类型：学位论文

【摘要】：微生物注浆加固技术是一项利用微生物成矿学的最新进展，即微生物诱导碳酸钙结晶技术，通过向松散砂土地基中低压传输微生物细胞以及营养盐（尿素与CaCl2的混合液），最终在砂土孔隙中快速析出碳酸钙胶凝结晶，改善地基力学性能。微生物注浆加固技术具有注浆压力低、传输距离远、扰动小、工期短、加固效果明显和低耗能等优势，是目前液化地基加固研究的前沿问题。本文主要通过标准动三轴及振动台试验来检测微生物注浆技术是否能够用于液化地基加固，并针对试验中发现的问题，对微生物注浆配方及注浆方案进行了调整。首先，概要介绍了微生物注浆加固技术的原理、方法以及国内外研究现状，，给出了适用于液化砂土地基加固的微生物注浆方法。其次，通过标准动三轴及小型振动台试验，研究了微生物注浆加固液化砂土的动力反应，尤其是抗液化性能，并与传统的碎石桩挡墙加固地基进行了对比。试验结果表明，微生物注浆加固液化砂土的抗液化性能显著提高，且固化效果高于碎石桩挡墙。最后，针对国内外微生物注浆技术在液化砂土加固研究中存在的问题与不足，笔者对固定液浓度、砂土颗粒级配、注浆速度、砂土相对密实度、平均粒径等因素对微生物传输的影响进行了详细的研究。实验结果表明，固定液浓度对微生物在砂土内的传输影响较大，易造成微生物的不均匀分布。根据这一研究结果，笔者对微生物配方及注浆方案进行了调整，并通过动三轴试验、无侧限单轴压缩UCS试验及不排水三轴压缩CU试验，测试了调整后微生物注浆加固砂样的受力变形性能，尤其对动力反应进行了测试和分析。试验表明，采用25mM/L固定液、1ml/min的注浆速度，有利于提高菌液在砂柱内传输的均匀性。经过2批次注浆后，固化砂样的抗液化强度高于Dr=85%的密砂砂样；经4批次注浆后，固化砂样在CSR=0.5时，动力加载3000次，轴向应变仅为0.3%，且孔压无明显变化。可见，调整后的微生物注浆技术，菌液用量及注浆批次都有大幅减少，固化时间缩短至1-2d，且CaCO3胶凝分布不均匀现象有所减缓，固化强度能够得到充分发挥。这为该技术应用于实际工程迈出了重要的一步。
[Abstract]:Microbial grouting reinforcement technology is a new development of microbiological metallogeny, that is, microorganism induced calcium carbonate crystallization technology. Through the transport of microorganism cells and nutrient salts (urea and CaCl2 mixture) to the loose sand foundation, the calcium carbonate cementitious crystallization was rapidly precipitated in the pores of sand soil. Improve the mechanical properties of the foundation. Microbial grouting reinforcement technology has the advantages of low grouting pressure, long transmission distance, small disturbance, short construction period, obvious reinforcement effect and low energy consumption. It is the frontier problem of liquefaction foundation reinforcement at present. This paper mainly through the standard dynamic triaxial test and shaking table test to test whether the microbial grouting technology can be used in liquefaction foundation reinforcement and to solve the problems found in the test. The formula and scheme of microbial grouting were adjusted. Firstly, the principle, method and research status of microbial grouting reinforcement technology are introduced briefly, and the microbial grouting method suitable for liquefaction sand foundation reinforcement is given. Secondly, through standard dynamic triaxial test and small shaking table test, the dynamic response, especially the liquefaction resistance, of microorganism grouting reinforced liquefaction sand is studied. The experimental results show that the liquefaction resistance of the soil reinforced with microbial grouting is significantly improved and the solidification effect is higher than that of the gravel pile retaining wall. Finally, in view of the problems and shortcomings of microbial grouting technology in the study of liquefaction sand reinforcement at home and abroad, the author of fixed liquid concentration, sand particle grading, grouting speed, sand relative compactness. The effect of average particle size on microbial transport was studied in detail. The experimental results showed that the concentration of fixed solution had a great effect on the microbial transport in sand. It is easy to cause the uneven distribution of microorganisms. According to the results of this study, the formulation and grouting scheme of microorganism are adjusted, and the dynamic triaxial test is carried out. Unconfined uniaxial compression UCS test and undrained triaxial compression CU test were used to test the mechanical and deformation properties of sand samples strengthened by microbial grouting, especially the dynamic response was tested and analyzed. The results show that the injection rate of 25 mm / L fixed liquid / min is beneficial to improve the uniformity of the bacterial liquid transport in the sand column. After 2 batches of grouting. The liquefaction resistance of solidified sand samples is higher than that of dr-85% dense sand samples. After 4 batches of grouting, when CSR = 0.5, dynamic loading is 3000 times, axial strain is only 0.3 and pore pressure has no obvious change. It can be seen that after the adjustment of microbial grouting technology, the amount of bacterial liquid and grouting batches have been greatly reduced, the curing time is shortened to 1-2 days, and the uneven distribution of CaCO3 gelation phenomenon has been slowed down. The solidification strength can be given full play, which is an important step for the application of this technology in practical engineering.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU472

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