为了探究微生物诱导碳酸钙沉淀(MICP)技术改良膨胀土膨胀特性的效果和作用机理,利用产脲酶菌CGMCC 1.368 7,开展了MICP拌和法处理膨胀土的膨胀特性试验。通过正交试验研究了反应液配比和Ca2+浓度对MICP拌和法处理膨胀土自由膨胀率、无荷膨胀率、CaCO3百分生成量的影响及其变化规律,揭示了MICP改良膨胀土的微观机理。结果表明:经MICP拌和法处理后,膨胀土的膨胀特性得到显著改善;当反应液配比为1∶1、Ca2+浓度为2.0 mol/L时,膨胀土自由膨胀率最大降低了44.4%;当反应液配比为1∶3、Ca2+浓度为2.0 mol/L时,体膨胀率减小了92.2%,膨胀含水率降低了24.9%。MICP技术通过胶结土颗粒、充填土体孔隙和离子置换作用,降低膨胀土颗粒的亲水性,减小土颗粒间的排斥作用,减弱膨胀土的膨胀势。研究成果验证了基于MICP技术拌和法改良膨胀土膨胀特性的可行性。
Abstract
The effectiveness and mechanism of MICP (Microbial Induced Calcium carbonate Precipitation) improving the expansion characteristics of expansive soil were investigated via test of expansive soil mixed with urease-producing bacteria CGMCC 1.368 7. The effects of reaction solution ratio and Ca2+ molar concentration on the free expansion rate, unloaded expansion rate, and percentage generation of CaCO3 of expansive soil treated with MICP were studied by orthogonal experiments, and the microscopic properties of MICP-modified expansive soil were revealed. The swelling characteristics of expansive soil treated with MICP can be improved remarkably: when the ratio of reaction solution is 1∶1 and the concentration of Ca2+ is 2.0 mol/L, the free expansion rate of expansive soil is reduced by 44.4% at most; when the ratio of the reaction solution is 1∶3 and the concentration of Ca2+ is 2.0 mol/L, the volumetric expansion rate is reduced by 92.2%, and the expansion moisture content is reduced by 24.9%. MICP technology reduces the hydrophilicity of expansive soil particles, hinders the repulsion between soil particles, and weakens the expansion potential of expansive soil by cementing soil particles, filling soil pores and ion replacement. The research results verify the feasibility of improving the swelling properties of expansive soil by mixing based on MICP technology.
关键词
膨胀土 /
自由膨胀率 /
无荷膨胀率 /
MICP /
微观分析
Key words
expansive soil /
free swelling rate /
unloaded swelling rate /
MICP /
microanalysis
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基金
国家重点研发计划项目(2017YFC1501201);安徽省引江济淮集团有限公司科技项目(YJJH-ZT-ZX-20191031216)
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