MICP与MgO联合加固粉土试验

Experimental study on the combined effect of MgO and MICP for reinforcing silt

微生物诱导碳酸钙沉积(MICP)技术利用特定微生物分解尿素产生碳酸根离子,与钙离子结合沉积生成碳酸钙,可对土体进行胶结加固。相比传统的化学加固,MICP具有环境友好、使用灵活等优点,但也面临处理步骤较多、加固效果不够稳定等问题。提出将活性MgO与MICP相结合,利用MICP反应提供氧化镁碳化所需的CO_(2),进一步提升加固效果。溶液试验表明,加入MgO会使溶液pH有所增加,使尿素水解速率降低;用MgO替代CaCl_(2)时的碳酸盐生成量低于使用CaCl_(2)时的生成量。粉土的加固试验结果表明,在粉土中掺入MgO然后进行MICP注浆处理,可有效降低试样崩解率并提高无侧限抗压强度,且掺入高活性MgO的效果更好。当MgO掺量在5%~20%时,试样加固强度与MgO掺量成线性正相关关系。相比仅使用MICP进行处理或仅在粉土中拌入MgO,MgO与MICP联合加固的强度更高,需要的处理次数更少。微观测试结果表明,MgO与MICP联合加固的试样中生成大量花瓣状或片状碱式碳酸镁,广泛分布在颗粒间和颗粒表面,起到了更强的胶结作用。

Specific microorganisms are utilized to decompose urea and produce carbonate ions by microbial induced calcite deposition(MICP) technology,which combines with calcium ions to deposit and form calcium carbonate for reinforcing soil.MICP has advantages such as environmental friendliness and flexible usage compared to traditional chemical methods,but there exist disadvantages such as more treatment steps and unstable reinforcement effects.As a low-carbon technology,active MgO carbonization is applied in the reinforcing soil.CO_(2) required for MgO carbonization is provided by MICP reaction.Thus,active MgO was combined with MICP to further improve the reinforcement effect in this study.Experimental research on the combined effect of MgO and MICP to reinforce silt was carried out.The results show that the pH of solution is increased by adding MgO,which decreases the hydrolysis rate of urea.The amount of carbonate generated when replacing CaCl_(2) with MgO is lower than when using CaCl_2.The reinforcement tests of silt show that the sample disintegration rate can be reduced effectively by mixing MgO into soil and conducting MICP treatment,which improves the unconfined compressive strength.The reinforce effect is better when is at high activity MgO content.The reinforced strength is linear positive correlated with the MgO content when it is in the range of 5% to 20%.Compared to the samples treated by pure MICP or by mixing only MgO in silt,higher strength is provided by the combined effect of MgO and MICP,which reduces process steps.XRD test shows that a considerable amount of basic magnesium carbonate is generated in the combined reinforced sample,indicating that sufficient carbonization reaction occurs.The microscopic test results indicate that large amounts of petal or sheet basic magnesium carbonate are generated in the sample reinforced by MgO and MICP,which are widely distributed in the gap and on the surface of particles,enhancing cementation effect.The common problem of uneven reinforcement when using only MICP treatment can be effectively improved by the combination of MgO and MICP method.