镁的引入对微生物加固砂土试验影响

微生物沉积碳酸盐技术（MICP）是土木工程领域中一种新型的地基处理技术，该技术主要通过微生物诱导产生的碳酸盐沉淀胶结砂土颗粒，从而提高其力学性能。目前，MICP加固过程中Ca2+作为生成CaCO3沉淀的主要来源，但是对其他金属离子和矿化产物以及矿化产物之间结合作用的相关研究较少。本文选取了6种不同的Mg2+/Ca2+摩尔比工况，通过碳酸盐沉淀试验和无侧限抗压强度试验，分析了MICP技术处理砂土影响的效果。利用扫描电子显微镜和X射线衍射仪，初步探讨了微生物固化砂土的机理。结果表明，随着Mg2+/Ca2+摩尔比的增加，固化后砂样的碳酸盐含量降低；较低Mg2+/Ca2+的摩尔比提高了其无侧限抗压强度；在Mg2+/Ca2+=0.1/0.4时，砂样的强度获得最大值；但较高Mg2+/Ca2+的摩尔比抑制了碳酸盐的析出，降低了其强度；随着镁/钙摩尔比的增大，矿物成分含有方解石、球霰石和镁方解石等各种混合物，矿物成分发生了变化。

Study on the Effect of Magnesium on the Experiment of Microbial Reinforcement of Sand

Microbially induced carbonate precipitation (MICP) is a new technology of foundation treatment in the field of civil engineering. The technology improves the mechanical properties mainly through carbonate precipitation and cementation of sand particles induced by microorganisms. At present, Ca2+ is the main source of CaCO3 precipitation in the process of micp reinforcement, but there are few studies on the interaction between other metal ions and mineralized products. In this paper, six different conditions of Mg2+/Ca2+ molar ratio are selected. By?means?of?carbonate?precipitation?test?and?unconfined?compressive?strength test, the effect of micp on sand solidification is analyzed. The mechanism of microbial solidification of sand was preliminarily discussed by means of scanning electron microscope and X-ray diffractometer. The results show that with the increase of Mg2+/Ca2+ molar ratio, the content of carbonate in solidified sand decreases; the lower molar ratio of Mg2+/Ca2+ increases the unconfined compressive strength; and the strength reaches the maximum value when Mg2+/Ca2+=0.1/0.4; but with the increase of Mg2+/Ca2+ molar ratio, the precipitation of carbonate is inhibited and the strength is reduced; With the increase of Mg2+/Ca2+ molar ratio, the mineral composition contains various mixtures such as calcite, globular aragonite and magnesium calcite, and the mineral composition changes.