石灰-沸石粉改良膨胀土强度特性及微观机理研究

Strength Characteristics and Microscopic Mechanism of Expansive Soil Improved by Lime-Zeolite Powder

针对膨胀土胀缩性造成的工程病害问题及石灰改良膨胀土产生的污染问题,以河南南阳地区膨胀土为研究对象,制备素膨胀土及不同石灰和沸石粉掺量的改良土试样。对试样进行无侧限抗压试验、自由膨胀率试验、三轴试验、X射线衍射(XRD)分析和扫描电子显微镜(SEM)测试,研究石灰-沸石粉复合改良膨胀土的强度特性及微观加固机理。结果表明:石灰改良和石灰-沸石粉复合改良均能有效增强土体的强度并降低自由膨胀率,复合改良效果更好,石灰和沸石粉的最佳掺量分别为6%(质量分数)和12%(质量分数);石灰改良土和复合改良土的应力-应变曲线转化为应变软化型;石灰的加入显著提升了膨胀土的黏聚力,随着沸石粉掺量的递增,复合改良土三轴抗剪强度不断增大,内摩擦角呈先增大后减小的趋势;沸石粉与石灰发生火山灰反应,生成大量胶凝物质,填充土体孔隙并使微观结构更加密实,增强土颗粒间的摩阻力,宏观层面上土体强度增强。

Aiming at the engineering disease problems caused by expansion and contraction of expansive soil and the pollution problems caused by lime improved expansive soil,this paper taked the expansive soil in Nanyang area of Henan province as the object of study,and prepared the specimens of vegetal expansive soil and improved soil with different dosages of lime and zeolite powder.The unconfined compressive test,free expansion rate test,triaxial test,X-ray diffraction(XRD)analysis and scanning electron microscope(SEM)test were carried out to study the strength characteristics and microscopic reinforcement mechanism of the lime-zeolite powder composite improved expansive soil.The results indicate that lime improvement and lime-zeolite powder composite improvement can effectively improve the strength of soil and reduce the free expansion rate,and the composite improvement effect is better.The optimum content of lime and zeolite powder is 6%(mass fraction)and 12%(mass fraction),respectively.The stress-strain curves of lime improved soil and composite improved soil are transformed into the strain-softening type.The addition of lime significantly improves the cohesion of the expansive soil.With the increase of zeolite powder content,the triaxial shear strength of composite improved soil increases continuously,and the internal friction angle increases first and then decreases.Zeolite powder reacts with lime to form a large amount of cementitious material,which fills the pores with soil and makes the microstructure more dense,increases the frictional resistance between soil particles,and increases the strength of the soil at the macro-level.