工业固废磷石膏可以很好的提升土体强度，但会增加土体脆性，而纤维加筋技术可以改良土体塑性，两种材料协同可起到互补作用。以陕西杨凌黄土为研究对象，通过无侧限抗压强度试验探究磷石膏改良黄土的最优掺量；基于该掺量开展直剪试验探究纤维加固黄土的最优掺量；最后通过扫描电镜试验（SEM）探究磷石膏协同聚丙烯纤维改良黄土的微观机理。研究结果表明：当磷石膏单掺黄土进行改良加固时，随磷石膏质量占比增大，改良后黄土的无侧限抗压强度先增大后减小，磷石膏掺入黄土的最优掺量为12%。基于磷石膏改良黄土的最优掺量，掺入聚丙烯纤维，发现随着聚丙烯纤维掺比增大，试样的峰值强度、粘聚力和残余强度先增大后减小，内摩擦角持续增大；微观试验表明磷石膏改良黄土和聚丙烯纤维协同磷石膏改良黄土均可以增大土粒间的胶结作用，填充土粒间孔隙；聚丙烯纤维在黄土中会形成纤维团将土颗粒包裹，从而为土粒提供拉应力，提升土样塑性。

Phosphogypsum, as one of the industrial solid wastes, can enhance the soil strength but will increase soil brittleness. While the fiber reinforcement technology can improve the soil plasticity. The synergy of the two materials, i.e., phosphogypsum and fiber, can play a complementary role in improving the mechanical properties of soils. The loess from Yangling, Shaanxi Province, is used to explore the optimal mix ratio of phosphogypsum in the loess by unconfined compressive strength tests. And then, the optimal mix ratio of fiber in the mixture of phosphogypsum and loess was investigated by the direct shear test based on the mixture ratio above. Finally, the microscopic mechanisms of loess improvement with phosphogypsum and polypropylene fibers was examined through scanning electron microscopy (SEM). The results showed that the unconfined compressive strength of the loess increases first and then decreases with an increase in the phosphogypsum mass when the phosphogypsum is mixed with the loess for reinforcement. And the optimal mix mass ratio of phosphogypsum in the loess is 12% in this study. The polypropylene fibers were then mixed into the mixture of phosphogypsum and loess based on the optimal mix mass ratio of phosphogypsum in the loess. It can be found that the peak strength, cohesion, and residual strength of the mixture sample increase first and then decrease, while the internal friction angle increase, with an increase in the polypropylene fiber content. The microscopic test results also indicated that the phosphogypsum and polypropylene fibers significantly enhance the cementation and fill the void among soil particles. Polypropylene fibers in loess can forms fiber clumps to wrap the soil particles. Thereby, it can provide tensile stress and improve the plasticity for the soil sample.

TU375.4

国家自然科学基金项目青年项目，中国博士后科学基金，陕西省自然科学基础研究计划资助项目