基于ERT技术的微生物矿化固砂过程监测研究∗

Study on the Cementation Process of Microbial‑induced Calcite Precipi‑ tation Treated Sand Using ERT Technique

摘要:

微生物诱导碳酸钙沉淀(MICP)技术在土体改良方面具有良好的应用前景，同时兼顾了生态环境效益。为了对 MICP 固砂过程进行实时监测，提出将高密度电阻率层析成像技术(ERT)与 MICP 相结合的方法，通过开展相应的室内试验，验证方法的可行性。试验过程中，将石英砂填入高度 60 mm、直径 176 mm 的圆柱模具，并在四周设计了 16 个电极，采用喷洒工艺在砂土表面限定区域进行了三轮 MICP 处理，利用自主研发的 ERT 系统对不同处理阶段的试样进行了电阻率测试，对比分析了 MICP 处理过程中试样内部电性参数的空间变化规律。结果表明：(1) MICP 处理过程中，处理区域呈现低电阻率特征，低电阻区的范围与电阻率大小主要与菌液和胶结液在砂土介质中的入渗扩散过程有关。(2)对 MICP 固化砂样进行洗盐风干后，之前处理区域由低电阻区转变为高电阻区，主要是因为微生物诱导生成的碳酸钙胶结作用导致砂土介质的密实度增大。(3)利用 ERT 技术可以有效追踪 MICP 处理过程中砂土内部电阻异常区的形成与扩展，并与 MICP 固砂过程与固化效果建立联系，说明采用 ERT 技术监测 MICP 固砂过程具有可行性，为研究 MICP 固砂机制和评价固化效果提供了新的技术思路。

Abstract:

Microbial-induced calcite precipitation (MICP) technique has promising application pros? pects in soil improvement field for its ability to take into account the ecological environmental benefits. In order to study the cementation process of MICP-treated sand， a method combining the electrical re? sistivity tomography (ERT) technique and MICP technique is proposed. An indoor experiment was carried out to verify the feasibility of the method. Quartz sands were filled into a cylindrical mold with a height of 60 mm and a diameter of 176 mm， and 16 electrodes were inserted around it. Three rounds of MICP treatments were performed on the specified area of the sand sample surface with the spraying method. The self-developed ERT system was used to test the resistivity distribution of the sample at different treatment stages， and then the variation of internal electrical parameters of the samples was analyzed during the MICP process. The results show that：(1) In the process of MICP treatment， the treated sand area presents low resistivity. The range and resistivity value of the low-resistivity area mainly depend on the infiltration and diffusion process of bacterial solution and cementation solution in the sand sample.(2) After washing off the salt from the MICP-treated sand， the resistivity value of the MICP-treated sand increased， resulting in an increase of density.(3) ERT technique can effective? ly track the formation and expansion of the sand area with abnormal resistivity during the MICP pro? cess and establish a connection between the MICP curing process and the cementation effect， which shows that the ERT technique is feasible for monitoring the MICP process. This study provides new technical ideas for studying the mechanism of MICP-treated sand and evaluating the cementation effect.