利用微生物矿化技术加固粉土试验研究

Experimental Study on Reinforcing Silt by Microbial Mineralization

利用微生物矿化技术加固土体已成为土木工程的研究热点,但目前的处理对象主要为松散砂土,关于加固粉土的研究比较缺乏.本文以海相粉土为研究对象,选用巴氏芽孢杆菌为微生物、采用尿素和氯化钙为胶结液对粉土进行处理.由于微生物难以渗入孔喉尺寸小的粉土,采取将菌液与粉土拌合制样,然后入渗若干轮胶结液的加固方法.水稳定性和无侧限抗压强度试验表明,该方法能对粉土进行整体加固,胶结液浓度和入渗轮数对加固效果有明显影响.随着胶结液入渗轮数和浓度的增加,试样中沉积的CaCO_(3)逐渐增多,但高胶结液浓度1.5 mol/L时的强度较低.针对试样处理后强度增幅有限的问题,对试验方法进行了改进:菌液在土中密封贮留12 h后即开始入渗后续的胶结液.对比发现,改进方法后试样的无侧限抗压强度得到了明显提高.处理后试样的扫描电镜(SEM)结果表明,改进后土中沉积生成的六面体碳酸钙晶体尺寸更大,能更有效地将土颗粒进行胶结.

Reinforcing soil with microbial mineralization technology has become research focus in civil engineering.However,the treatment mainly concentrates on loose sand,and the research of silt treatment is not sufficient so far.In this study,Sporosarcina pasteurii was selected as bacteria and the cementation solution was comprised of urea and calcium chloride.Due to the difficulty of bacteria penetrating into silt pore throat,the method of premixing bacteria with soil followed by cementation solution percolation repeatedly was adopted.Water stability and unconfined strength tests indicate the samples can be reinforced by this method,and the concentration and number of treatments of cementation solution have significant influence on improvement effect.The amount of precipitated CaCO_(3) increased with treatments and concentration of cementation solution,nevertheless the strength decreased remarkably when the concentration reached 1.5 mol/L.In view of the limited strength increase of samples,the treatment method is improved:the cementation solution percolate into sample right after bacterial fluid has rested in sample for 12 hours in sealing condition.The results shows that the strength with improved method has been significantly increased.The SEM results of the treated samples show that the size of hexahedral calcium carbonate crystals deposited in the improved soil is larger and the soil particles can be cemented more effectively.