HUANG Rongpin,SHAO Guanghui,CHEN Feiyang.Morphological evolution characteristics of cementation area in sand solidified by single point biogrouting[J].Journal of Forestry Engineering,2019,4(06):158-164.[doi:10.13360/j.issn.2096-1359.2019.06.022]





Morphological evolution characteristics of cementation area in sand solidified by single point biogrouting
南京林业大学土木工程学院,南京 210037
HUANG Rongpin SHAO Guanghui CHEN Feiyang
School of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China
微生物固土技术 微生物单点注浆 胶结区 形态演变 重力下沉
microbial induced calcite precipitation single point biogrouting cementation area evolution of morphology gravitational force subsidence
微生物注浆加固地基时,胶结区的形态和特性是影响地基承载性能的核心因素。为揭示微生物注浆固土胶结区形态演变特征及其影响因素,采用立式平板试验槽开展微生物单点注浆固化砂土试验,研究不同轮次注浆过程中胶结区形态变化以及微生物诱导胶结矿物的分布规律。试验结果显示:菌液通过注浆孔注入砂土后,在竖直平面内发生二维渗流扩散,细菌浓度以注浆口为中心呈非对称分布,OD600等值线前锋面在水平扩展的同时,向下方偏转。水平方向上,菌液浓度OD600值受土体的反滤与吸附作用控制,在水平的扩散路径上沿程衰减,受此影响,微生物诱导产生的胶结碳酸钙含量也呈现显著的沿程衰减现象; 竖直方向上,菌液浓度OD600值受细菌重力下沉与土体反滤、吸附作用共同影响,注浆口以下的衰减速度明显低于注浆口以上。胶结液的重力下沉现象明显,使细菌诱导产生的碳酸钙分布与细菌浓度分布衰减规律不再一致,碳酸钙优先在槽底处沉积。经过多轮注浆后,稳定加固体底部的碳酸钙生成量最高,表层的碳酸钙生成量最低。受碳酸钙空间分布的影响,胶结区在无侧向边界约束时呈堆积锥体扩展,而在有侧向边界约束时呈U形叠加扩展。研究结果表明,影响胶结区形态演变的主要因素是土体对细菌的反滤与吸附作用、细菌的重力下沉、胶结液的重力下沉,这些因素也是导致微生物注浆固土胶结不均匀的内在原因。
The key factors which influence the bearing performance of foundation during the biogouting treatment are morphology and properties of cementation area.For revealing the morphological evolution characteristics of cementation area and related factors, the repeated single point biogrouting experiments were conducted in a vertical test tank, and the morphological variation of cementation area and distribution of calcite induced by microbe were investigated.The experimental results showed that two-dimensional seepage diffusion of bacterial liquid occurred in the vertical plane, and the bacteria was asymmetrically distributed around the injection point when the bacterial liquid was injected into sand through a grouting hole.The contour front of OD600 deflected downward as it expanded horizontally.As observed in the horizontal direction, the bacterial concentration was attenuated along the diffusion path with the effect of soil filtration and adsorption.This resulted in the calcite precipitation to decrease gradually with the increase in the distance from injection point.However, owing to the self-weight of bacteria, soil adsorption and filtration, the decay rate of bacterial concentration below the injection point was lower than that above the injection point from the vertical observation.The gravity subsidence of cementation solution was obvious, so that the distribution of calcite induced by microbe was no longer consistent with the distribution of bacteria.Therefore, the calcite was deposited preferentially at the bottom of the test tank.After several rounds of the grouting, the calcite precipitation at the bottom of the reinforcement became the highest, whereas the calcite on the top surface of the reinforcement was the lowest.Influenced by the spatial distribution characteristics of calcite, the shape of cementation area took on a accumulation cone when the grouting boundary was open, and changed to the U shape when the boundary effect existed.Based on the above findings, it is concluded that the main factors to determine the evolution characteristics of cementation area are the spatial distribution characteristics of bacteria and the gravity subsidence of bacteria and cementation solution.In addition, these factors are also the internal causes of uneven cementation by the biogrouting.


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收稿日期:2019-04-09 修回日期:2019-08-10 基金项目:国家自然科学基金(51578293)。 作者简介:黄容聘,男,助理实验师,研究方向为环境岩土和微生物岩土工程。E-mail: njfuhrp@njfu.edu.cn
更新日期/Last Update: 2019-11-10