【摘要】 【目标】为解决膨胀土用作路基填料时易导致路基膨胀变形和沉陷等工程问题，以枣潜高速公路某施工路段的膨胀土为研究对象，选取草木灰和粉煤灰为膨胀土的改性材料。【方法】通过自由膨胀率试验、无荷载膨胀率试验及直接剪切试验，研究不同改性配比条件下的改性膨胀土膨胀率和抗剪强度的变化规律，并通过XRD测试和扫描电镜观测，从细观角度探索改性膨胀土的微观改性机理。【结果】掺入草木灰和粉煤灰将改变膨胀土内部的颗粒成分和结构，有效降低其膨胀性，并显著提高其抗剪强度。当采用草木灰和粉煤灰联合改性时，10%草木灰和14%粉煤灰的改性土的自由膨胀率从48%降低至34%;在100 kPa和300 kPa的竖向压力下的抗剪强度分别提升了46.70%和42.71%;改性土的黏聚力和内摩擦角分别从14.20 kPa和22.57°提升至23.61 kPa和30.20°。经改性后的膨胀土试样出现了C—S—H、C—A—H等新的水化物。改性土的内部由于改良材料和水化物的填入致使孔隙率明显减少，大孔径几乎消失，土颗粒之间接触更紧密，从而提升了膨胀土的强度，降低了膨胀率。【结论】研究结果将为解决膨胀土路基变形问题提供科学依据，为实现固废资源在路基改性中的应用提供新的思路，具有良好的工程应用前景。更多还原

【Abstract】 [Objective] This study investigates the swelling deformation and settlement of swelling soil subgrade. It took the swelling soil from Zaoyang-Qianjiang expressway as the study object, as well as taking plant ash and fly ash as modifying materials. [Method] This study carried out experiments on free swelling ratio, unloaded swelling ratio and direct shear strength. It analyzed the variation rules of swelling ratio and shear strength of modified swelling soil with different proportions of modifying materials. Meanwhile, the micro-modification mechanism of swelling soil was investigated from a fine-grained point of view through X-ray diffraction tests and scanning electron microscopy observations. [Result] The incorporation of plant ash and fly ash changed the particle composition and structure within soil, which effectively suppressed the swelling of soil and significantly increased the shear strength. The free swelling ratio decreased from 48% to 34% when modified with 10% plant ash and 14% fly ash; the shear strength increased by 46.70% and 42.71% respectively under 100 kPa and 300 kPa of vertical pressure; the cohesion of modified soil increased from 14.20 kPa to 22.57 kPa; and the angle of internal friction increased from 23.61° to 30.20°. The modified swelling soil exhibited new hydration products, e.g., C—S—H and C—A—H. The internal porosity of modified soil was significantly reduced due to the filling of modifying materials and hydrates. The large pore size almost disappeared. The contact among soil particles was more compact. It improved the strength of swelling soil and reduced the swelling ratio. [Conclusion] The findings will provide a scientific basis for solving the deformation of swelling soil subgrade; as well as provide a new idea for realizing the application of solid waste resources in subgrade improvement, which has good engineering application prospects.更多还原