生物酶辅助氧化镁碳化过程砂土加固试验研究

Experimental study on enzyme enhanced magnesia carbonation process for soil stabilization

基于微生物或酶诱导碳酸盐沉积(即MICP和EICP)过程的固土技术具备固化强度高、环境友好等特点,但是目前也存在处理效率低、耗时长等局限。为克服这些局限,研究一种新型高效的生物固土技术,即基于植物脲酶辅助氧化镁碳化(酶辅助碳化)过程的固土法,探索其处理方法、效果和作用机理,并与单纯的氧化镁碳化、EICP和水泥等方法进行比较。结果表明,采用酶辅助碳化加固法时,一遍处理强度可达0.92 MPa,且试样的强度显著高于单纯氧化镁处理(0.30 MPa)、EICP处理(0.28 MPa)和水泥处理(0.69 MPa)。酶辅助碳化加固法处理试样的制备方式对强度影响较大。与注入法相比,采用拌和法处理的试样强度高了3倍。此外,添加少量脱脂奶粉后,酶辅助碳化加固法处理试样的强度进一步提升了约70%,达到1.30 MPa。通过微观结构和矿物成分分析发现,酶辅助碳化处理后,固化物填满了砂颗粒之间的孔隙,将砂颗粒结合在一起,形成稳定网格空间结构,与不添加脲酶的试样相比,其中的水合碳酸镁混合物含量较高,中间产物水镁石含量较低。

The soil solidification technology based on microbial-or enzyme-induced carbonate precipitation process has the characteristics of high strength and environmental friendliness.However,it has limitations such as low treatment efficiency and time-consuming.This paper studies the treatment method,effect and mechanism of another biological soil solidification technology based on the urease-enhanced magnesia carbonization process.Comparisons were made against pure magnesia carbonation,enzyme-induced calcium carbonate precipitation(EICP) and Portland cement.The results show that when the urease-enhanced magnesia carbonization treatment method is used,a higher strength(0.92 MPa) can be obtained after one treatment,and the strength of the sample is significantly higher than that of the samples treated with pure magnesia(0.30MPa),EICP(0.28 MPa) or Portland cement(0.69 MPa).The preparation method of the urease-enhanced magnesia carbonization treatment sample also has great influence on the strength.Compared with the one-phase injection method,the strength of the sample treated by the pre-mixed method was 3 times higher.In addition,the strength of the urease-enhanced magnesia carbonization treatment sample was further improved by about 70%,and the highest strength reached 1.30 MPa,with the addition of small amount of non-fat milk powder.Through microstructural and mineralogical analysis,it was found that after urease-enhanced magnesia carbonization treatment,the solidified materials filled the pores between the sand particles,cemented the sand particles together,and formed a stable spatial structure.It could also be seen that soil treatment by ureaseenhanced magnesia carbonization led to higher hydrated magnesium carbonates content,and lower brucite content.