基于微生物诱导碳酸钙沉积技术的黏性土水稳性改良

Water stability improvement of clayey soil based on microbial induced calcite precipitation

采用微生物诱导碳酸钙沉积(MICP)技术对黏性土进行改性处理,以改善其水稳性与抗侵蚀能力.利用喷洒法将配制的微生物菌液及胶结液先后喷洒至黏性土表层进行MICP处理,并开展一系列崩解试验,通过数字图像处理技术对土样的崩解过程进行定量分析和评价.通过颗粒分析试验研究MICP改性前后土样粒度组分的变化,通过扫描电子显微镜(SEM)分析土样的微观结构特征.结果表明:1)素土在浸水后发生快速崩解,而在相同的时间内MICP改性土样则能较好地保持原始结构,水稳性更强;2)崩解指数是描述土体崩解过程和评价土体水稳性的定量指标.MICP改性土样的崩解速率远低于素土,且最终稳定后的崩解指数仅为素土的50%;3)MICP改性能显著改变土样的粒度组分,具体表现为细颗粒质量分数减少,粗粒土质量分数增加;4)微生物诱导所产生的碳酸钙填充了土样中的大孔隙,并在土颗粒之间形成有效的胶结,极大提高土颗粒之间的联接强度,这是MICP技术提高土体水稳性的主要作用机制.

Microbial induced calcium carbonate precipitation(MICP)technology was adopted to improve the water stability and the erosion resistance of clayey soil.The prepared microbial solution and the cementation solution were sprayed to the surface of clayey soil by a spraying method for MICP treatment.A series of disintegration tests were carried out,and the digital picture processing technique was used to quantitatively analyze and evaluate the disintegration process.The grain size test was used to determine the change of particle size composition before and after MICP treatment,and the microstructure of the soil samples was further analyzed by the scanning electron microscope(SEM).Results showed that compared with the rapid disintegration of the raw soil after being immersed in water,the MICP treated soil sample can maintain its original structure in the same time,and the water stability is stronger.The slaking index(SI)is a quantitative indicator of describing the process of soil slaking and evaluating the water stability.The disintegration rate of the MICP treated soil was far lower than that of the raw soil,and the final SI of the MICP treated soil was only half of that of the raw soil.The MICP treatment can significantly change the particle size composition of the soil sample,i.e.the mass fraction of fine particles was reduced and the mass fraction of coarse particles was increased.Calcium carbonate precipitated by microorganisms,fills large pores of the soil,and the effective cementation between the soil particles greatly improves the strength of the connection between the soil particles,which is the main mechanism for MICP to improve the soil water stability.