基于微生物矿化的砂体胶结强度及耐久性试验研究

Experimental Study on Cementation Strength and Durability of Sand Body Based on Microbial Mineralization

微生物诱导碳酸钙沉淀技术(MICP)是岩土工程领域中新兴的新型绿色环保地基加固技术之一。基于砂土固化的力学性能和微观测试,研究了MICP技术的固化效果。研究结果表明,微生物水泥胶结砂柱最高强度可达37.9 MPa,抗渗性能可从胶结前的1.72×10-2 cm/s提高至7.66×10-7 cm/s;经100次冻融循环后,试件外观完整,无明显缺陷和掉砂;冻融50次时强度损失率为17.0%,胶结砂体具有良好的抗冻耐久性能。40 mm×40 mm×160 mm棱柱体标准试件抗压强度为13.5 MPa,抗折强度为4.5 MPa;70 mm×70 mm×70 mm立方体标准试件抗压强度为8.6 MPa。微观结构检测可知,石英砂表面与颗粒之间沉积着不同数量的方解石,随着胶结强度的增加,方解石沉积量逐渐提高至趋于稳定,生成量为10%~25%,砂柱孔隙率由34.8%逐渐降至12.1%,且微观孔结构逐渐细化、密实。

Microbial-induced calcium carbonate precipitation(MICP)is a new environmental protection foundation treatment technology emerging in the field of geotechnical engineering in recent years.The solidification effect of MICP technology is studied based on the mechanical properties and microcosmic test of sand body solidification.The results show that the maximum strength of microbial cement cemented sand column can reach 37.9 MPa,and the impervious property can be increased from 1.72×10-2 cm/s to 7.66×10-7 cm/s;after 100 freeze-thaw cycles,the specimen has a complete appearance without obvious defects and sand removal;the strength loss rate is 17.0%after 50 freeze-thaw cycles,indicating the cemented sand body has good frost resistance and durability.The compressive strength and flexural strength of standard specimens of 40 mm×40 mm×160 mm cylindrical body are 13.5 MPa and 4.5 MPa respectively.The compressive strength of standard 70 mm×70 mm×70 mm cube specimen is 8.6 MPa.According to the micro structure examination,different amounts of calcite are deposited between the quartz sand surface and particles.With the increase of cementation strength,the calcite deposition gradually increases to a stable amount of 10%-25%,the porosity of sand column gradually decreases from 34.8%to 12.1%,and the microscopic pore structure gradually becomes refined and dense.