Meter-scale MICP improvement of medium graded very gravelly sands: Lab measurement, transport modelling, mechanical and microstructural analysis
Meter-scale MICP improvement of medium graded very gravelly sands: Lab measurement, transport modelling, mechanical and microstructural analysis
复制标题
中等级配非常砾石砂的米级 MICP 改进：实验室测量、传输建模、机械和微观结构分析
DOI：
10.1016/j.enggeo.2023.107275
复制
发表时间：
2023
影响因子：
7.4
通讯作者：
Sang G
中科院分区：
文献类型：
--
作者：
Sang G
微生物诱导碳酸盐沉淀法是一种很有前途的地基加固方法。迄今为止，大多数研究都集中在均匀干净砂的MICP处理上，很少有研究在大规模上对更能代表原位沉积物的级配良好的土壤进行。本研究提出了一个实验室米级的中级配非常砾石砂的MICP测试。MICP处理在径向流动池（直径：10.1 m;厚度：10.15 m）中进行，注入井位于中心，恒定水头位于外边界，以复制现场条件。连续监测流动池内流出物样品的水性化学。运输建模和废水采样监测的电导率和pH值表明，在一般情况下，有良好的交付和反应的细菌和化学品在径向流动池，与一些优先的流动路径存在。MICP处理的土壤进行了一系列的水力和力学试验和微观结构分析。有趣的是，对于给定的方解石含量（9.2-15.1%），生物水泥中级配极砾砂的强度（UCS值为2.6-7.4 MPa）高于处理均匀土壤的可比研究中的强度。这可以归因于较高的初始密度的颗粒与颗粒的接触点中的中等等级的土壤，和一个高颗粒的棱角性，导致颗粒联锁和较长的颗粒与颗粒的接触表面，可以看出，从扫描电子显微镜图像。两个核心的固结排水三轴试验表明，在100千帕的有效围压下的峰值偏强度为5.9 MPa和3.7 MPa，剪切过程中剪切带的清晰形成，相比，峰值偏强度为0.5 MPa的未处理的土壤。MICP处理明显提高了材料的剪切强度和刚度。研究表明，优先流动路径的形成可能是一个挑战，在现场应用中产生均匀的生物胶结的MICP。我们建议，成功的MICP治疗异质土壤将需要一个精心设计和执行良好的现场调查计划，可以识别，先验，任何显着的高或低渗透性的特点，在土体内的几何形状，以告知最终的MICP治疗策略。
Microbially induced carbonate precipitation (MICP) is a promising biogrouting method for ground improvement. Most studies to date have focused on MICP treatment of uniform clean sands, with few studies having been conducted at large-scale on well-graded soils more representative of in situ deposits. This study presents a laboratory meter-scale MICP test on medium-graded very gravelly sands. The MICP treatment was conducted in a radial flow cell (diameter: ∼1 m; thickness: ∼0.15 m) with an injection well located at the centre and a constant hydraulic head at the outer boundary to replicate field conditions. Aqueous chemistry of the effluent samples inside the flow cell was continuously monitored. Transport modelling and effluent sampling monitoring of the electrical conductivity and pH show that, in general, there was good delivery and reaction of the bacteria and chemicals in the radial flow cell, with some preferential flow paths being present. The MICP-treated soil was subjected to a series of hydraulic and mechanical tests and microstructural analysis. Interestingly, the biocemented medium-graded very gravelly sands had higher strengths (UCS values of 2.6–7.4 MPa) for a given calcite content (9.2–15.1%) than those in comparable studies where uniform soils have been treated. This can be attributed to the higher initial density of grain-to-grain contact points in the medium-graded soil, and a high grain angularity which resulted in particle interlocking and longer grain-to-grain contact surfaces, as can be seen from Scanning Electron Microscopy images. Consolidated-drained triaxial tests on two cores showed peak deviatoric strengths of 5.9 MPa and 3.7 MPa under an effective confining stress of 100 kPa, with the clear formation of shear bands during shearing, compared to a peak deviatoric strength of 0.5 MPa determined for the untreated soil. MICP treatment clearly enhanced the shear strength and stiffness of the material. The study shows that formation of preferential flow paths may be a challenge for producing uniform biocementation in field applications of MICP. We propose that successful MICP treatment in heterogeneous soils will require a well-designed and well-executed site investigation programme that can identify, a priori,the geometry of any significant high or low permeability features within the soil body to inform the final MICP treatment strategy.