微生物诱导碳酸钙沉淀修复三合土裂缝效果研究

Repair effect of tabia cracks with microbially induced carbonate precipitation

裂缝是土遗址的一种典型破坏形式,其存在会降低结构的性能。另外,裂缝为雨水渗入土体提供优势路径,显著劣化结构的力学性能。因此,土遗址裂缝的修复是其保护与加固的重要内容。三合土的主要成分之一是碳酸钙,应用微生物诱导碳酸钙沉淀(MICP)技术来修复和保护三合土遗址,不仅具有环境友好性,而且与基材的兼容性良好。将MICP技术在土遗址保护领域进一步扩展,以修复三合土的裂缝为研究目标,提出一种由微生物矿化过程主导的裂缝修复方法,并通过试验手段评价其修复效果。首先,进行MICP影响因素和加固土柱试验,确定修复裂缝的适宜细菌浓度、胶结液浓度、填充颗粒组合和注浆批次等参数。然后,利用以上适宜参数,修复预先破坏的三合土试样,并验证其修复效果。结果表明,当裂缝宽度为5mm时,经过MICP修复后试样的平均抗弯强度和抗剪强度恢复率分别为79.92%和88.54%,显示出令人满意的修复能力。但是,恢复率随着裂缝宽度的增加呈现下降的趋势。另外,静态接触角试验结果说明,MICP不但修复了裂缝,同时还增强了裂缝的疏水性。MICP技术可作为修复三合土裂缝的有效方法。

Cracks as a damage type of earthen sites not only destroy tabia structure integrity but also degrade mechanical properties due to providing preferential paths for rainfall infiltration. Therefore,the repair of tabia cracks is an important part of protection and reinforcement of earthen sites. Due to that calcium carbonate is one of the main components of the tabia,the use of microbially induced carbonate precipitation(MICP) technical to repair and protect the tabia is not only environmentally friendly but also compatible with the substrate. In this paper,a crack repair method dominated by MICP was proposed to repair the cracks of the tabia,and the repair effect was evaluated by experimental test. First,the influencing factors of MICP test and the reinforced soil column test were carried out to determine the suitable parameters for repairing cracks,including the concentrations of bacteria and cementation reagent,filled soil particles and the number of grouting cycles. Then,the pre-damaged tabia samples were repaired using MICP with the suitable parameters,and the repair effect was verified. The results show that,when the crack width is 5 mm,the recovery ratios of the average flexural strength and shear strength of the specimens repaired by MICP are respectively 79.92% and 88.54%,showing a very satisfactory repairing ability,while that the recovery ratio tends to decrease as the crack width increases. In addition,the static contact angle test results show that the MICP not only repairs the crack but also enhances the hydrophobicity of the crack. MICP technology can be used as an effective method to repair cracks in the tabia.