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高校地质学报 ›› 2021, Vol. 27 ›› Issue (6): 746-753.DOI: 10.16108/j.issn1006-7493.2020106

• 微生物岩土与地质工程专辑 • 上一篇    下一篇

基于石灰石粉钙源的微生物固化砂土试验研究

程瑶佳,唐朝生*,刘 博,泮晓华,王殿龙,吕 超,李 昊   

  1. 南京大学 地球科学与工程学院,南京 210023
  • 出版日期:2021-12-20 发布日期:2022-01-07

Experimental Sthdy on Microbial Solidified Sand Based on Calcium Source Extracted from Limestone Powder

CHENG Yaojia,TANG Chaosheng*,LIU Bo,PAN Xiaohua,WANG Dianlong,LYU Chao,LI Hao   

  1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
  • Online:2021-12-20 Published:2022-01-07

摘要: 微生物诱导碳酸钙沉积(MICP)作用是一种新型的土体改良技术。钙源作为MICP反应中重要的反应物,对微生物诱导碳酸钙沉积的效果有重要的影响。目前应用最广泛的钙源——氯化钙(CaCl2),具有成本高,环境污染性大的缺点。为此,文章提出利用石灰石粉提取钙源,通过在石灰石粉中加入乙酸溶液,释放钙离子用于微生物固化土体。通过开展无侧限抗压强度试验以及微观结构的扫描电镜观测、碳酸钙含量测定等分析,验证利用石灰石粉提取的钙源用于微生物诱导碳酸钙沉积作用固化土体的可行性,同时与醋酸钙和氯化钙固化砂柱进行了对比分析。研究结果表明:(1)石灰石粉用于微生物固化土体具有可行性,固化后砂柱的强度和碳酸钙含量较高,结构完整性高;(2)不同钙源固化砂柱的力学特性不同但均呈典型的脆性破坏模式,其中醋酸钙固化砂柱的无侧限抗压强度略高于石灰石钙源固化砂柱,氯化钙固化砂柱的无侧限抗压强度则远低于前两者且表面更加粗糙,孔隙更多,破坏后的完整性更低;(3)不同钙源固化砂柱的碳酸钙含量不同。醋酸钙和石灰石钙源固化砂柱的碳酸钙含量相近,而氯化钙固化砂柱中碳酸钙含量较低。不同钙源固化砂柱的碳酸钙含量和无侧限抗压强度基本呈正相关关系;(4)醋酸钙和石灰石钙源固化砂柱中砂土颗粒的表面和接触点间均沉积大量碳酸钙,碳酸钙晶体主要为薄片状堆叠的方解石。氯化钙固化砂柱中碳酸钙沉积量低于前两者,碳酸钙晶体主要为六面体状的方解石;(5)不同钙源主要通过影响微生物成矿过程的晶型、晶貌、晶体含量、晶体分布及胶结特征来改变固化效果。

关键词: 微生物诱导碳酸钙沉淀, MICP, 石灰石粉, 强度, 碳酸钙, 微观结构

Abstract: Microbial induced calcite precipitation (MICP) is a new soil improvement technology. As an important reactant in MICP reaction, calcium source has an important effect on the effect of microbial induced calcite precipitation. At present, the most widely used calcium source— calcium chloride (CaCl2), has the disadvantages of high cost and high environmental pollution. Therefore, this paper proposes to extract calcium source from limestone powder by adding acetic acid solution to limestone powder for microbial solidification of soil. The unconfined compressive strength test, scanning electron microscope observation of microstructure and calcium carbonate content test were carried out to verify the feasibility of using calcareous powder to extract calcium source for microbial induced calcite precipitation. The results show that: (1) It is feasible to extract calcium source from limestone powder for microbial solidification of soil. The strength and calcium carbonate content of sand column after solidifying is high and the structural integrity is high. (2) The mechanical properties of solidified sand columns treated by different calcium sources are different. The sand columns solidified by three kinds of calcium show typical brittle failure mode. But the unconfined compressive strength of sand columns solidified by calcium acetate is slightly higher than that of sand columns solidified by calcium source from limestone, and the unconfined compressive strength of sand columns solidified by calcium chloride is much lower than that of the first two. Sand columns solidified by calcium chloride are rougher and have more pores on the surface than the other two. They also have lower integrity after destruction. (3) The content of calcium carbonate in solidified sand columns treated by different calcium sources is different. Sand columns solidified by calcium acetate and calcium source from limestone have almost no difference, but sand columns solidified by calcium chloride have less calcium carbonate content. There is a positive correlation between calcium carbonate content and unconfined compressive strength of sand columns solidified by different calcium sources. (4) A large amount of calcium carbonate is precipitated between the surface and contact point of sand particles in the sand column solidified by calcium acetate and calcium source from limestone. Calcium carbonate crystal is mainly thin stacked calcite. Sand columns solidified by calcium chloride have less calcium carbonate precipitation than the first two, and calcium carbonate crystal is mainly hexagonal calcite. (5) Different calcium sources change the soildifying effect mainly by affecting the crystal appearance, crystal content, crystal distribution and cementation characteristics of microbial mineralization.

Key words: microbial induced calcite precipitation, MICP, limestone power, strength, calcium carbonate, microstructure

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