微生物胶结砂土三轴试验及微观结构研究

微生物固化(microbial-induced calcite precipitation,简称为MICP)技术是岩土工程领域新兴的一种地基处理技术。利用该技术可胶结松散土颗粒,改善土体的力学特性。基于一系列试验(X射线衍射、扫描电镜、CD剪切、碳酸钙定量化学试验)测试分析了胶结砂样微观结构与力学性能提高的联系、胶结物含量与砂样c'、φ'值之间的关系。研究结果表明:微生物诱导沉积产生的碳酸钙晶体主要粘附在骨架颗粒接触部位,并高度聚集封堵颗粒孔隙形成连接键,从而产生胶结作用提高试样的力学性能;菌液浓度、注液时间、营养盐浓度会影响碳酸钙的沉积量;碳酸钙含量与砂样的力学性能提高有较好关联性。试验中胶结砂样的碳酸钙含量达到5.39%时,其抗剪强度、凝聚力、内摩擦角可分别提高423%,333%,35.7%。

Triaxial test and micro analysis of microbial cemented sandy soil

A new ground treatment technique, microbial-induced calcite precipitation (MICP), has recently emerged in geotechnical engineering，which utilizes the MICP to cement loose particles together and therefore the mechanical properties of soil can be enhanced. Based on the test (X ray diffraction, scanning electron microscopy, triaxial shear test, CaCO3 quantitative chemical tests), the connection between the change of microstructure and the improvement of mechanical properties of cemented sandy soil, and the relationship between the cement content and sandy soil physical mechanical indexes are obtained. From the test results, it is found that the calcite crystal mainly adheres on particle contact face and highly aggregates, thus blocking the pore and forming link bonds, then the mechanical properties of the samples are improved by the cementation of the particles. The concentration of bacteria liquid，the time of injection and the concentration of nutrients can affect the content of settled calcite. A good correlation between the content of calcite and the improvement degree of mechanical properties of the sandy soil is obtained. In the test, when the calcite content of cemented sandy soil samples reach to 5.39%, the strength, cohesion and internal friction angle will increase by 423%, 333% and 35.7%,respectively.