围海造陆工程中MICP技术固化黑砂硬壳层的基础研究

Fundamental Study of Black Sand Crust Cementation Using MICP in Artificially Made Land Projects

在围海造陆工程中,采用真空预压法固化淤泥质地基时需要在淤泥表层铺设一层黑色细砂层,来满足施工机械对地基承载力的要求。采用MICP技术固化这种黑砂,在快速增强其承载力的同时大大节约黑砂用量。主要研究了胶结溶液的静置时间、浓度、流速等对MICP固化黑砂的影响,分析了钙离子的利用率、固化砂柱碳酸钙的分布和无侧限抗压强度。试验结果显示,采用MICP技术固化黑砂是可行的,能够快速将砂柱的抗压强度提高至1.91 MPa,满足工程应用需要。试验数据结果显示,固化后砂柱的无侧限抗压强度与碳酸钙含量呈现幂指数关系。根据分析,MICP固化黑砂过程中适宜采用的胶结溶液的静置时间为3h,浓度为0.75 M,流速为10mL/min。

In the artificial made land project,the soft marine cohesive soils usually require improvement and the vacuum preloading is a frequently used soil improvement method.Before the vacuum can be applied,a layer of black fine sand is applied over the soft mucky clay so that a working platform can be created for the construction equipment.This paper presents the cementation of black fine sand by using Microbial-Induced Calcite Precipitation（MICP）method to reduce the thickness of the sand without reducing the bearing capacity.The effect of solution set up time,concentration and the velocity on the MICP sand cementation is evaluated by analysis the calcium ion utilization,distribution of calcium carbonate in the solidified sand column and the unconfined compressive strength.The results indicate that it is feasible to use MICP method for the rapid sand cementation.The solidified sand column can reach an unconfined compressive strength of 1.91 MPa in a short period of time.The results also show that the unconfined compressive strength has an index relationship with the concentration of calcium carbonate in the solidified sand column.The best result from the solution with 3 hour set up time,concentration of 0.75 M with a velocity of 10 ml/min.