微生物固化含黏粒花岗岩残积土的强度机理研究

微生物诱导碳酸钙沉淀(MICP)可以改善花岗岩残积土的工程力学特性,但其固化效果受黏粒含量的影响较大。在花岗岩残积土中掺加不同黏粒进行MICP固化试验,对固化后的土样测定其碳酸钙含量,并进行无侧限抗压强度试验,研究不同黏粒含量对固化效果的影响。在此基础上,开展了固化后试样的核磁共振试验(NMR),从细观角度研究黏粒含量对花岗岩残积土的固化机理。结果表明：微生物固化土样的强度主要包括土体骨架强度和碳酸钙胶结强度两部分,前者受土体自身孔隙率影响,后者则通过碳酸钙晶体的沉积量影响固化土样的强度；随着黏粒含量的提高,试验土样内孔隙率缩小,碳酸钙的沉积量也随之减小,固化后的强度提高不明显；掺加适量的红黏土(最优黏粒含量为60%),在不改变土样其他性能条件下可以获得较高的固化强度。

Study on strength mechanism of clay-bearing granite residual soil solidified by microorganism

Microbially induced calcium carbonate precipitation (MICP) can significantly improve the engineering mechanical properties of granite residual soil, but its solidification effect is greatly affected by the clay content. MICP curing test was carried out by adding different clay particles in granite residual soil. The calcium carbonate content of solidified soil samples was measured, and the unconfined compressive strength test was carried out to study the effect of different clay content on the curing effect. On this basis, nuclear magnetic resonance (NMR) test was carried out to study the curing mechanism of clay content on granite residual soil from the microscopic point of view. The results show that the strength of microbial solidified soil samples mainly includes the strength of soil skeleton and the strength of calcium carbonate cementation. The former is affected by the porosity of soil itself, and the latter affects the strength of solidified soil samples through the deposition of calcium carbonate crystals. With the increase of clay content, the porosity in the test soil sample is reduced, and the deposition of calcium carbonate is also reduced, and the strength after increase significantly. Adding appropriate amount of red clay (optimal clay content is 60%) can obtain higher curing strength without changing other properties of soil samples.