微生物诱导碳酸钙沉淀胶结加固泥岩试验研究

Experimental Study on Mudstone Reinforcement by Microbial Induced Calcium Carbonate Precipitation Cementation

在水环境作用下,泥岩容易发生软化、崩解等现象。应用微生物诱导碳酸钙沉淀(MICP)技术处理重塑泥岩试样,研究了试样颗粒粒径、制备方式及MICP处理方式对碳酸钙沉淀物的影响,探讨了MICP方法治理泥岩稳定性的可行性。基于X射线衍射(XRD)、扫描电镜(SEM)、X射线能谱分析(EDS)、直接剪切等试验测试胶结试样,分析了胶结试样微观结构及力学性能的变化。结果表明,选用直径为0.25~1 mm的20 g重塑泥岩制备环刀样,在相同浓度营养盐条件下采用一次浸泡菌液的方式可以在试样中形成方解石型碳酸钙晶体;碳酸钙晶体沉积在颗粒接触处或填充在孔隙中形成“胶结桥”,产生胶结效果而增强试样的力学性能;不同垂直压力下胶结试样强度逐渐增加而趋于稳定值,表现为应变硬化的特征,黏聚力与内摩擦角分别提高288%、8.66%,说明微生物胶结泥岩具有较好的应用价值。

In a watery environment,mudstone is easy to be softened and disintegrated.The microbial induced calcium carbonate precipitation(MICP)technology was used to treat remolded mudstone samples.The effects of sample particle size,preparation method,and MICP treatment method on calcium carbonate precipitation were studied,and the feasibility of MICP method to control mudstone stability was discussed.The cemented samples were tested by X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray energy spectroscopy(EDS),direct shear test,etc.The microstructure and mechanical properties of the cemented samples were analyzed.The results show that remolded mudstone with a diameter of 0.25~1 mm was selected to prepare the ring knife sample,and calcite-type calcium carbonate crystals could be formed in the sample by using a single soaking solution under the same concentration of nutrient salt.Calcium carbonate crystals were deposited at the contact of the particles or filled in the pores to form a“bonded bridge”,which produced a cementation effect and enhanced the mechanical properties of the sample.The strength of cemented samples increased gradually and tended to be stable under different vertical pressures,which was characterized by strain hardening.The cohesion and internal friction angles increased by 288%and 8.66%,respectively,indicating that microbial cemented mudstone has good application value of engineering.