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以合肥典型膨胀土为研究对象,利用石灰与十六烷基三甲基溴化铵(CTMAB)混合物作为添加剂对膨胀土进行改良,通过界限含水率试验、直剪试验、不固结不排水三轴压缩试验、自由膨胀率试验和扫描电镜(SEM)试验,对比分析了两种不同膨胀潜势膨胀土改良前、后基本物理力学性质变化情况和改良效果,并基于双电层理论进行改良微观机制分析。试验研究结果表明:膨胀土改良后,黏粒含量减小,粉粒含量增多,塑性指数降低,亲水性减弱,膨胀潜势得到有效抑制,自由膨胀率低于40%,变为非膨胀土,抗剪强度得到提高。通过SEM观察微观结构发现:改良土土粒产生团聚作用并胶结成整体,土颗粒间胶结力增强,水稳定性提高。CTMAB与石灰相互促进、激发,形成协同作用,通过离子交换、吸附、包裹、胶结等一系列复杂的表面物化反应,使土粒扩散层厚度变薄,膨胀土对水“敏感性”降低,强度提高,工程性质得到明显改善。
Taking Hefei typical expansive soil as the research object, the expansive soil was modified by the mixture of lime and cetyltrimethylammonium bromide (CTMAB) as an additive, which was tested by the limit moisture content test, direct shear test, unconsolidated undrained Axial compression test, free-expansion test and SEM test. The changes of basic physical and mechanical properties and the improvement effect of the two expansive expansive expansive soils before and after the modification were compared. Based on the theory of electric double layer, Mechanism analysis. The experimental results show that: after the expansive soil is improved, the clay content decreases, the content of the powder increases, the plasticity index decreases, the hydrophilicity decreases, the expansion potential is effectively inhibited, the free expansion rate is less than 40% , The shear strength is improved. SEM observation of the microstructure showed that the improvement of soil particles produced agglomeration and cementing into a whole, the cementing force between soil particles increased and the water stability improved. CTMAB and lime mutually promote, stimulate and form a synergistic effect. The thickness of the diffusion layer of soil particles is thinned by a series of complex surface physicochemical reactions such as ion exchange, adsorption, wrapping and cementing, and the expansive soil has a lower water sensitivity , Strength increased, the nature of the project has been significantly improved.