发泡颗粒轻量土长期交通荷载下渐进性变形机制及破坏标准

A lot of silt are generated in water conservancy projects, shipping projects and water environment management projects in China every year. Waste plastic foam has the characteristics of light weight, large volume, difficult degradation. The waste soil pollution and white pollution have restricted the sustainable development of economic society in China. As a kind of filling material, foamed particles in light weight soil can be made from Weihe River silt, EPS particles (expanded polystyrene), Portland cement. It can turn waste into treasure, and protect environment. Based on soil mechanics, non-continuous medium mechanics, elastic-plastic mechanics, progressive deformation mechanism and failure criteria of foamed particles in light weight soil under long-term traffic loading are researched by dynamic triaxial tests, digital camera visualization tracking technology and digital image processing technology, and particle flow numerical simulation. After research the dynamic stress-strain relationship and the damping characteristics, the soil surface crack extension evolution law, and the interaction mechanism between EPS particles soft inclusion and solidified soil particles, the relationship between the macro mechanical properties and the microstructure is discussed, then the progressive deformation mechanism of foamed particles in light weight soil under long-term traffic loading are revealed. Base on the traditional soil failure criterions, combining with the microstructure characteristic parameters evolution law, and the stress field, the displacement field among the particles, the dynamic strength difference mechanism caused by the different failure criterions is studied, then a new dynamic failure criterion of light weight soil is proposed. The results provide theoretical support for the promotion of the use of light weight soil, and it has a great significance for efficiently dealing with dredging silt and waste plastic foam.

我国每年在水利工程、航运工程和水环境治理工程中都会产生大量清淤淤泥，加之废弃塑料泡沫质量轻、体积大、难降解，废土污染与白色污染已经严重制约我国经济社会可持续发展。采用渭河疏浚泥、发泡聚苯乙烯颗粒、水泥，制备发泡颗粒轻量土作为填土材料，可以变废为宝，保护环境。本项目以土力学、非连续介质力学、弹塑性力学为理论基础，采用动三轴试验、高清数码摄像及数字图像处理技术、颗粒流数值仿真等方法，从动应力-应变关系与阻尼特性、土样表面裂纹扩张演化规律、EPS颗粒软夹杂与固化土颗粒相互作用机制三方面，探索宏观力学特性与细观结构之间的关系，阐明轻量土长期交通荷载下渐进性变形机制。以传统土壤破坏标准为基础，对照细观结构特征参数演化规律，以及颗粒间应力场、位移场情况，分析不同破坏标准所引起的动强度差异机制，建立轻量土的破坏标准。成果为轻量土推广使用提供理论支持，并且对于高效稳定利用疏浚泥与废弃塑料泡沫具有重要意义。

我国每年在水利工程、土木工程中都会产生大量清淤淤泥，加之废弃塑料泡沫质量轻、体积大、难降解，废土污染与白色污染已经严重制约我国经济社会可持续发展。采用渭河疏浚泥、发泡聚苯乙烯颗粒、水泥，制备发泡颗粒轻量土作为填土材料，可以变废为宝，保护环境。通过无侧限抗压强度试验、三轴试验、动三轴试验，研究了发泡颗粒混合轻量土的力学特性。成果：（1）建立了轻量土配方公式，为轻量土配合比设计与产业化施工提供了理论依据。（2）建立了轻量土最优含水量模型与击实密度模型，并且通过试验检验了模型的正确性。（3）建立了轻量土在最优含水量、流动上限、流动下限3种界限含水量时混合土的力学指标的数理关系。（4）提出了轻量土一维固结理论三大假设：EPS不能完全视为孔隙；假设EPS的比重为1来计算轻量土的孔隙比；当环境应力小于结构强度时，轻量土可以视为均质饱和土。（5）建立了静力荷载作用下轻量土破坏取值标准，从理论上推导出了各种常规标准之间的数理联系，并且通过试验检验了破坏取值标准的合理性。（6）提出了静力荷载作用下轻量土强度机理：轻量土总强度=凝聚力±剪胀+摩擦+挤碎与重排列。（7）采用不同应力状态试验进行验证，比较试验骨干曲线理论值与实测点，相同应变对应动应力差值小于10kPa，说明Hardin-Drnevich模型能够用来描述EPS颗粒混合轻量土的骨干曲线。（8）EPS颗粒混合轻量土在动荷载作用过程中，动应变增长比较平稳，没有出现变形急速陡转的情况，而且压应变明显大于拉应变，所以选择5%压应变作为破坏标准。随着围压和水泥掺入比的增大，EPS颗粒混合轻量土动强度增大；随着EPS颗粒掺入比的增大，EPS颗粒混合轻量土动强度减小。相比较于重塑黄土动强度，不同配比的EPS颗粒混合轻量土的动强度增大幅度为20.8%～232.9%。（9）水泥掺入比和EPS颗粒掺入比对EPS颗粒混合轻量土的动强度参数均有较大的影响，振动次数对动粘聚力的影响较大而对动内摩擦角的影响甚微。研究成果可为轻量土推广使用提供理论支持。