盐蚀环境下微生物矿化岩土材料的冻融特性研究

基于MICP技术将松散砂粒改良成微生物矿化岩土材料,通过室内冻融循环实验,研究矿化材料在4种不同的冻融环境中的表观形貌、质量损失率、饱和含水率、无侧限抗压强度随冻融循环周期的变化规律,以及利用NMR测试手段分析材料的孔隙变化。结果表明:随着冻融周期增加,在4种冻融液中矿化材料均伴随剥落现象,无侧限抗压强度均呈逐渐减小趋势,质量的损失和饱和含水率的增加严重影响了材料的抗冻性能,且在5%Na₂SO₄溶液中矿化材料的粉化速度较快,质量损失最大,劣化速度最快,NMR图谱中弛豫时间大于200 ms的未冻水含量在冻融过程变化最大,是造成样本质量的损失和强度的破坏的主要原因;在去离子水溶液中样本的抗冻能力也较弱,次于Na₂SO₄溶液;在3%NaCl溶液和混合溶液中由于NaCl的存在降低材料的凝固点,使得材料的抗冻能力延长,此研究为微生物矿化岩土材料在寒冷地区的工程应用提供基础实验依据。

Study on Freeze-thaw Properties for Microbial MineralizationGeotechnical Materials in Salt Corrosion Environment

Based on MICP technology, the loose sandy soil was improved into microbial mineralized material. The changing rules of freeze-thaw properties of microbial mineralization materials, such as the apparent morphology, mass loss ratio, saturated water content, and unconfined compressive strength, with freezing and thawing cycles were studied through indoor freeze-thaw cycles experiment. Four different freeze-thaw solutions were used in this study. The results show that mineralized material appears spalling phenomenon in aqueous solution and salt solution with the increase of freeze-thaw cycles. Unconfined compressive strength decreases in the whole process of experiment. The loss of mass and the increase of saturated water content heavily affect the anti-frost properties of material. In 5% Na₂SO₄ solution, mineralization material''s pulverization rate is faster and the quality loss rate is the largest, the damage is the fastest and most serious; in the NMR spectrum, when the relaxation time is longer than 200ms, the change of the unfrozen water content is the largest in the freeze-thaw process, which is the main reason for the loss of the quality of the specimens and the destruction of the strength. The frost resistance of the specimens in the deionized aqueous solution is also weaker than in Na₂SO₄ olution. The freezing point of the mineralization material reduces and the freezing resistance prolongs due to the presence of NaCl in the 3% NaCl solution and the mixed solution. This research provides basic experimental evidence for the engineering application of microbial mineralized material in cold regions.