微生物灌浆加固液化砂土地基的动力反应研究

Dynamic response of liquefiable sand foundation improved by bio-grouting

饱和松砂地基在地震等周期性荷载作用下易发生液化,而松砂边坡在降雨或地下水位上升过程中易发生"静态"液化,这些都易造成路基沉陷、滑坡、地下管道及隧道的上浮等与液化相关的工程灾害。相对传统的地基加固技术,微生物灌浆加固技术是利用一项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,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。微生物灌浆加固技术具有扰动小、工期短、加固效果明显和低耗能等优势,是目前地基加固研究的前沿问题。通过标准动三轴及振动台试验来检测微生物灌浆是否能够用于液化地基加固。首先,概要介绍了微生物灌浆加固技术的原理、方法以及国内外研究发展水平,给出了适用于液化砂土地基加固的微生物灌浆方法。其次,通过标准动三轴及小型振动台试验,研究了微生物灌浆加固液化砂土的抗液化性能,以及其它动力性能,并与传统的液化地基加固方式进行了对比分析。试验结果表明,微生物灌浆加固砂柱及模型地基的抗液化性能显著提高。可以说,微生物灌浆技术在液化砂土地基加固方面具有潜在的工程实用价值和广阔的应用前景。

The liquefaction induced in loose and saturated sand foundations by dynamic loading such as earthquakes and the ＂static＂ liquefaction induced during rainfall and groundwater rise in loose sand slopes can lead to catastrophic damages such as the subsidence of road embankments,landslides and the floating of embedded structures like pipelines and tunnels.Compared with the traditional ground improvement methods,one of advances in bio-mineralization enables the rapid microbial induced carbonate precipitation,which is introduced by transporting the bacterial cells and nutrient solutions into loose sand foundations for the purpose of ground improvement.This new ground improvement process is called bio-grouting.It is the leading edge of ground improvement research,which has many advantages such as small disturbance,short construction period,notable reinforcement and low energy consumption.This study is attempted to investigate whether the bio-grouting is applicable to the improvement of liquefiable ground through dynamic triaxial tests and shaking table tests.First,a brief introduction to the research,development of microbial induced carbonate precipitation and bio-grouting technology is presented,and a practical bio-grouting treatment method applicable to improvement of liquefiable sand foundations is described.Second,the anti-liquefaction performance and other dynamic performance of the bio-grouting sand ground are studied through dynamic triaxial and small scaled shaking table tests,and a comparison between the bio-grouting and the traditional ground improvement methods is made.The test results show that the anti-liquefaction performance of bio-grouting samples and models is greatly improved.In short,the bio-grouting technology has potential to be used in engineering applications and broad application prospect in liquefiable sand foundations.