【作者】 王亮；

【导师】 刘松玉；

【作者基本信息】 东南大学 ， 岩土工程， 2019， 硕士

【摘要】 使用水泥作为土体固化材料会产生大量碳排放,活性MgO是有效的水泥替代品,经碳化后可以取得良好的固化效果,且实现了二氧化碳循环利用,具有很高的环境效益。现有MgO搅拌土碳化多局限于处理浅层地基,本文基于东南大学岩土所关于MgO碳化的已有研究成果,首次提出通过透气管桩通气碳化MgO搅拌土的碳化复合桩技术。进行了室内单元体试验、模型试验和现场单点试验,验证了该方法的可行性。论文的主要研究内容和成果如下:（1）采用三轴柔性壁室内渗透试验对活性MgO碳化固化粉土和粉质黏土的渗透特性进行了系统研究,发现固化后土体渗透系数处于10^-510^-6 cm/s数量级。活性MgO碳化土的渗透系数随MgO掺量的增加而降低,与相同掺量下水泥固化土的渗透系数处于同一数量级;MgO碳化粉土的渗透系数明显大于碳化粉质黏土的渗透系数;当MgO固化粉土和粉质黏土碳化6.0 h时,相应的渗透系数达到最小(10^-6 cm/s);通气压力对MgO碳化固化土的渗透系数影响不大。（2）通过室内单元体试验,证明了透气管桩碳化法可以取得与三轴密闭碳化基本接近的碳化效果。透气管桩的有效影响范围内,不同距离的搅拌土所能获得的碳化效果基本一致。碳化时间较短或碳化通气压力较小时,近距离处碳化效果更好。碳化过程对透气管桩强度增长有益,碳化6.0 h后可达初始强度的1.6倍。（3）通过室内模型试验,对透气管桩碳化法在粉土和淤泥质土中的应用效果进行了研究。通过温度、物理力学特性等指标对碳化效果进行了评价。试验结果表明通气碳化前需要预留足够的MgO水化时间;透气管桩碳化法的碳化效果沿深度基本均匀;受土颗粒、水分等阻碍,且由于气体运动方向的不定性,透气管桩碳化法存在有效碳化距离和最大碳化距离。本试验中200 kPa通气压力下有效碳化距离至少可达40 cm。（4）基于室内试验和现场单点试验,总结得出透气管桩碳化法的不同反应阶段特征,初步提出了透气管桩碳化法的现场施工工艺。更多还原

【Abstract】 The disadvantage of cement as soil solidifying material is that it produces a large amount of carbon emissions.Reactive MgO can achieve good curing effect after carbonization,and realization of carbon cycle,which has high environmental benefits.Therefore,it is an effective cement substitute.Based on the existing research results of MgO carbonization method from Institute of Geotechnical Engineering,Southeast University,the technology of carbonized composite pile based on permeable pipe pile was first put forward.Laboratory unit cell test,model test and field single-point test were carried out.The feasibility of this method is verified.The main contents and conclusions were drawn as follows:（1）The permeability characteristics of reactive MgO-carbonized silt and silty clay were systematically studied by using the triaxial flexible wall chamber permeability test.It was found that the permeability coefficient of the soil after carbonization was in the order of magnitude of10^-510^-6cm/s.The permeability coefficient of reactive MgO-stabilized soils decreases with the increase of MgO content.It is in the same order of magnitude compared with PC-treated soil with the same curing agent content.The permeability coefficient of carbonated silt is obviously larger than that of carbonated silty clay.When both the MgO-stabilized silt and silty clay are carbonized for 6.0 hours,the corresponding permeability coefficient could reach the minimum(10^-6cm/s).Ventilation pressure has little effect on the permeability coefficient of carbonated reactive MgO-stabilized soils.（2）Through the laboratory test,it is proved that the carbonization method of the permeable pipe pile can achieve the carbonization effect basically similar to that of the three-axis closed carbonization.Within the effective influence range of the permeable pipe pile,the carbonation effect of soil stirred at different distances is basically the same.With short carbonation time or small carbonation ventilation pressure,near carbonation effect is better.The carbonization process is beneficial to the strength growth of the permeable pipe pile.After 6 hours,it can reach 1.6 times of the initial strength.（3）The application of carbonization method of permeable pipe pile in silt and silty soil was studied through laboratory model test.The carbonization effect was evaluated by temperature,physical and mechanical properties.The results show that sufficient time for MgO to be hydrated before carbonization should be guaranteed.The carbonization effect using permeable pipe pile on mixed soil at different depths is basically the same.Due to soil particles,moisture and the uncertainty of gas movement direction,there are effective and maximum carbonization distances in this method.In this research,the effective carbonization distance can reach at least 40 cm under the ventilation pressure of 200 kPa.（4）Based on the laboratory test and field single point test,the characteristics of different reaction stages of carbonization method of permeable pipe pile are summarized.The site construction technology of carbonization method of permeable pipe pile is put forward preliminarily.更多还原