生蚝壳作为微生物固化砂土钙源的试验研究

微生物诱导碳酸钙沉淀（microbial induced calcium carbonate precipitation，MICP）是一种新兴的环保地基加固技术，使用该技术需消耗大量化学分析级试剂，如尿素、钙盐等，对环境等造成一定的不良影响。基于利用废弃资源的理念，选取厨余垃圾生蚝壳作为MICP固化砂土钙源，并与用硝酸钙、氯化钙作为钙源进行对比。通过无侧限抗压强度试验、渗透试验、碳酸钙质量分数测试、干密度试验和扫描电镜试验（SEM）等探讨该方法的可行性。试验结果表明，以生蚝壳为钙源的MICP固化砂柱的平均孔径最大，但其表观孔隙率最低，无侧限抗压强度、渗透系数、碳酸钙质量分数、干密度等物理力学指标均优于化学钙。SEM试验结果显示，不同钙源固化砂柱砂颗粒表面均有碳酸钙沉淀生成，生蚝壳钙源获得的碳酸钙沉淀晶体形态是表面比较粗糙，伴有微小孔隙的球体形态；硝酸钙获得的碳酸钙沉淀是介于球状和棱柱体之间的多棱角的簇状；氯化钙获得的碳酸钙沉淀呈现颗粒相互交错堆积的簇状。

An Experimental Study of Oyster Shell as Calcium Source for Microbial Solidification

Microbial-induced calcium carbonate precipitation (MICP) is an emerging environmentally friendly foundation reinforcement technology that requires the consumption of a large number of chemical analysis-grade reagents, such as urea, calcium salts, etc., which have certain adverse effects on the environment. Based on the idea of utilizing waste resources, oyster shells from kitchen waste were selected as calcium sources of MICP solidified sandy soil and compared with chemical calcium sources such as calcium nitrate and calcium chloride. Through unconfined compressive strength test, permeability test, calcium carbonate content test, dry density test and scanning electron microscopy (SEM), the feasibility of oyster shells as calcium source of MICP solidified sand was discussed. The experimental results show that the MICP solidified sand column with raw clam shells as the calcium source has the largest average pore size, but the lowest apparent porosity, and the physical strength indexes such as unconfined compressive strength, permeability coefficient, calcium carbonate content and dry density are all higher than chemical calcium. SEM test results show that different calcium source solidified sand column sand particles have calcium carbonate precipitation on the surface, and the calcium carbonate precipitated crystal obtained from the raw clam shell calcium source has a relatively fine surface with a small pore shape; and nitric acid obtained from calcium carbonate precipitate is in a cluster of polygonal angles between the spherical and prismatic bodies; and calcium chloride obtained from calcium carbonate precipitate exhibits clusters in which the particles are interlaced with each other.