Microbially induced cementation to control sand response to undrained shear
Microbially induced cementation to control sand response to undrained shear
复制标题
DOI：
10.1061/(asce)1090-0241(2006)132:11(1381
复制
发表时间：
2006-11-01
影响因子：
3.9
通讯作者：
Nusslein, Klaus
中科院分区：
文献类型：
--
作者：
DeJong, Jason T.;Fritzges, Michael B.;Nusslein, Klaus
目前改善砂工程性能的方法在方法、处理均匀性、成本、环境影响、场地可达性要求等方面多种多样。所有这些方法都有优点和缺点，并且仍然需要探索土壤改良的新可能性，特别是在适合开发的土地变得更加稀缺的情况下。本文介绍了一项研究结果，其中利用自然微生物生物过程在最初松散的湿陷性沙子中设计了胶结土基质。微生物诱导方解石沉淀（MICP）是利用微生物巴氏芽孢杆菌（一种普遍存在于天然土壤沉积物中的需氧细菌）实现的。将微生物引入到用尿素和溶解的钙源修正的液体生长培养基中的沙样本中。随后对样本进行胶结处理，以增加砂粒基质的胶结水平。通过使用弯曲元件测量剪切波速，对 MICP 和石膏水泥样本的结果进行无损评估。一系列各向同性固结不排水压缩（CIUC）三轴试验表明，经过 MICP 处理的试件表现出非塌陷应变软化剪切行为，与未经处理的松散试件相比，具有更高的初始剪切刚度和最终剪切能力。这种行为类似于石膏胶结样本的行为，代表了典型的胶结砂行为。 SEM 显微镜证实了胶结砂基质的形成，其中沉淀的方解石浓度在颗粒与颗粒接触处形成键。 X 射线成分图证实观察到的水泥粘结剂由方解石组成。
Current methods to improve the engineering properties of sands are diverse with respect to methodology, treatment uniformity, cost, environmental impact, site accessibility requirements, etc. All of these methods have benefits and drawbacks, and there continues to be a need to explore new possibilities of soil improvement, particularly as suitable land for development becomes more scarce. This paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose, collapsible sand. Microbially induced calcite precipitation (MICP) was achieved using the microorganism Bacillus pasteurii, an aerobic bacterium pervasive in natural soil deposits. The microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source. Subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix. The results of both MICP- and gypsum-cemented specimens were assessed nondestructively by measuring the shear wave velocity with bender elements. A series of isotropically consolidated undrained compression (CIUC) triaxial tests indicate that the MICP-treated specimens exhibit a noncollapse strain softening shear behavior, with a higher initial shear stiffness and ultimate shear capacity than untreated loose specimens. This behavior is similar to that of the gypsum-cemented specimens, which represent typical cemented sand behavior. SEM microscopy verified formation of a cemented sand matrix with a concentration of precipitated calcite forming bonds at particle-particle contacts. X-ray compositional mapping confirmed that the observed cement bonds were comprised of calcite.