土石混合料的应力应变特性及其本构模型研究

At present, the mountainous area high fill engineering has been widely used in the construction of the airport. Its subgrade post-construction settlement control is more difficult, which leads to settlement diseases and stability problems. The rock-soil aggregate mixture is used in the airport high fill engineering widely. But it contains different mixing proportion of earth and rock. And it will make the mechanical property of the rock-soil aggregate mixture be more complex. The subgrade settlement deformation and stability problems of airport high fill engineering can be rational analyzed whether or not. It largely depends on that the used constitutive model whether to objectively reflect the stress-strain characteristics of rock-soil aggregate mixture. But now, there is few research for this kind of constitutive model. So in the subject, from the angle of earth-rock mixture ratio and through experimental research, some laws that the basic features of rock-soil aggregate mixture under different earth-rock mixture ratio such as pore characteristics, compression, dilatancy shear shrinkage regularity, are concluded. And the influence of earth-rock mixture ratio on the stress-strain characteristic of the rock-soil aggregate mixture is analyzed. And combined with the unified hardening model (UH model), the simple, reasonable and practical three-dimensional elastic-plastic constitutive model of rock-soil aggregate mixture is developed which can consider the influence of the earth-rock mixture ratio on the stress and strain characteristic. And the material module development in the finite element software is completed. Finally, it is used for the simulation analysis of the subgrade deformation and stability problem of high fill airport engineering and the determination of the initial optimal earth-rock mixture ratio, which provides the guidance for practical engineering construction.

目前，山区机场建设中大量采用高填方工程，其地基工后沉降控制较难，导致出现沉降病害和稳定性问题，高填方工程中多采用土石混合料，由于其中含有不同混合比例的土和石，力学特性复杂，能否对机场高填方工程地基沉降变形及稳定性问题进行合理分析，很大程度上取决于所采用的本构模型是否客观反映了土石混合料应力应变特性，而目前对于这种本构模型的研究还很少。因此，本课题拟从土石混合比角度入手，通过试验研究，总结出不同土石混合比的土石混合料的孔隙特性及压缩、剪胀剪缩等基本特性规律，分析土石混合比对土石混合料的应力--应变特性的影响规律；结合统一硬化模型（UH模型），发展能够考虑土石混合比对应力应变特性影响的土石混合料的简单、合理、实用的三维弹塑性本构模型；并完成该模型在有限元软件中材料模块的开发；最后用于模拟分析机场高填方工程地基变形及稳定性问题及最优初始土石混合比的确定，为实际工程施工提供指导依据。

目前山区机场建设大量采用高填方工程，高填方地基沉降变形和稳定性问题是个亟待解决的重要问题。高填方工程中多采用土石混合料，由于其中含有不同比例的土和石，其力学特性复杂，能否对机场高填方工程地基沉降变形和稳定性问题进行合理分析，很大程度上取决于所采用的本构模型是否客观反映了土石混合料应力应变特性。含石量是影响土石混合料抗剪强度的重要因素，影响着内摩擦角和粘聚力，如果在本构模型中考虑含石量，将含石量和粘聚力及内摩擦角的关系引入进来，则能够更加合理的反映土石混合料的抗剪强度和应力应变特性，使得对实际高填方工程问题的分析更加合理。.因此，本课题基于统一硬化模型（UH模型），通过研究含石量与内摩擦角和粘聚力的关系，并基于扩展SMP准则和变换应力，将含石量引入到UH模型中，建立了考虑含石量的三维UH土石混合料模型，完成了对UH模型的改进，实现了土石混合料本构模型的建立；并应用当前屈服面与平均主应力轴的交点的变化规律作为考虑含石量UH模型加卸载的判断准则，实现了硬化和软化的统一考虑；并采用半隐式回映应力更新算法，将加卸载准则应用到应力更新算法中，实现了考虑含石量UH模型的有限元应用；然后应用考虑含石量UH模型的有限元程序对土石混合料的大型三轴试验进行了有限元分析，通过对计算结果和实测结果的比较，验证有限元程序的正确性，并分析了不同含石量和不同围压下土石混合料的应力应变规律；最后应用考虑含石量UH模型的有限元程序，对山区机场高填方地基进行了三维有限元分析，得到了地基沉降监测点的竖向位移随时间的变化曲线，并和不考虑含石量UH模型、修正剑桥模型（MCC模型）计算得到的曲线以及工程实测数据进行了比较，并得到了高填方地基的竖向位移云图、侧向位移云图、孔隙水压力云图和孔隙水压力随时间的变化曲线，从而得到了机场高填方地基的位移和孔隙水压力变化规律，并分析了不同含石量及填筑高度下机场高填方地基的安全稳定规律，说明了考虑含石量UH模型在分析山区机场高填方地基变形和稳定性方面的合理性，可为实际山区机场高填方地基工程施工提供指导依据，也可推广到高土石坝、高速公路和铁路等土石混合料路堤的沉降分析。