土体环境对微生物诱导碳酸钙沉积加固海相粉土的影响研究

生物地基处理技术利用微生物诱导碳酸钙沉积来加固土体,符合环境保护和可持续发展的要求,具有良好的发展前景。目前已取得的研究成果主要是针对简单离子化学环境下的松散砂土,对不同环境下的细粒土研究的较少。以江苏东部沿海地区的海相吹填粉土为研究对象,选用巴氏芽孢杆菌进行微生物注浆试验,定量分析温度、pH值、氯化盐含量、土体中胶结阳离子含量等土中的环境因素对加固效果的影响规律。结果表明:随着温度的升高、试样中生成的碳酸钙增加,但无侧限抗压强度并不是呈现出一直提高的趋势,而是存在一个峰值。偏碱性的环境有利于巴氏芽孢杆菌的工作,但过高的pH值会影响加固效果。土中的氯化盐含量过高时会抑制细菌的活性从而对加固产生不利影响。土中的胶结阳离子含量对微生物注浆的影响很小,可忽略不计。本次试验研究结果能为现场环境下采用MICP技术加固粉土提供有效的依据。

Effects of Soil Environment on Microbially Induced CalcitePrecipitation in Marine Silt

Biomediated soil improvement utilizes certain bacteria to precipitate calcite among soil particles, which has a bright prospect because it is in accordance with the requirements of sustainable development. The existing research results mainly focused on improving the soil composed of coarse particles such as sand; however, the fine-grained soil formed in different environments has not been well investigated. In the present study, bio-grouting experiments using Sporosarcina pasteuring were conducted to treat the marine silt collected from the eastern coastal areas of Jiangsu, China. The influences of environment temperature, pH value, the content of chlorate, and the contents of cementing cations were analyzed by quantitative tests in laboratory. The results indicated that the calcium carbonate precipated in the soil specimen increased with the rise of temperature, but the unconfined compression strength had a peak value instead of a linear increase with temperature. The meta-alkalescence environment is favorable for the work of Sporosarcina pasteuring; nevertheless, the reinforcement effect may be affected if the pH is too high. An exorbitant content of chlorate salt in the soil would prevent the activity of bacteria, and thus had an adverse impact on the strength of sample. The influence of cementing cation concentration in soil was so small that could be ignored. The research results may provide an effective guidance for actual soil grouting reinforcement using the method of microbial induced calcite precipitation.