高、低应力下粗粒土的破碎演化规律及统一本构模型研究

应力作用下粗粒土的破碎不仅影响土工结构的整体服役性能，而且挑战了经典土力学中土颗粒不可压缩不可破碎的基本假设。现有粗粒土破碎问题的研究主要集中在常应力水平，尚未建立粗粒土在高、低应力下的统一本构特性描述。本项目以钙质砂和堆石料两种典型粗粒土为研究对象，以破碎表征指标、破碎指标演化规律、破碎本构模型三大关键步骤为研究主线。首先，基于高应力侧限压缩试验及大应变环剪试验，揭示粗粒土极限级配的影响因素，提出合理的破碎表征指标。其次，开展不同应力路径三轴试验，定量描述不同荷载类型下粗粒土的破碎演化规律，建立考虑不同类型荷载对破碎发展差异的统一破碎演化模型。最后，提出适用于高、低应力下粗粒土的压缩模型、状态参数及临界状态线随破碎发展的动态演化模型，并最终建立高、低应力下的统一本构模型。预期成果可为我国在大工程建设领域提供重要的技术支撑，还将丰富粗粒土的理论研究体系。

Particle breakage of granular soils subjected to external loading not only affects the overall performance of civil infrastructures, but also challenges the theory of classic soil mechanics that soil particles are incompressible and unbreakable. To date, the studies on particle breakage of granular soils mainly focus on the constant stress level, a unified constitutive description of granular soils under low and high stresses has not been established. In this project, two typical granular soils (i.e., carbonate sand and rockfill material) are adopted as the research objects, and the three key steps (i.e., the breakage index, the evolution of breakage index, and the constitutive modelling of particle breakage) are taken as the main research lines. Firstly, a series of 1D-compression tests at high stresses and ring shear tests at large shear strains are conducted to explore the influencing factors of the ultimate gradation, and then to propose a reasonable breakage index. Secondly, a series of triaxial tests with different stress paths are carried out to quantitatively describe the evolution of particle breakage of granular soils subjected to different load types, and then to develop a unified evolution law considering of the load types. Finally, the compression model, the state parameter, and the dynamic evolution model of the critical state line as particle breakage progresses are proposed for the granular soils. A unified constitutive model is then developed for the granular soils under both low and high stresses. This project will not only offer many important technical advantages for the construction of large civil infrastructures, but also enrich our understanding of granular soils from the perspective of theoretical research.