高应力作用下粗粒土细观力学及坝工特性研究

More and more super-high dams have been under construction in the recent years, which causes great concerns about the mechanical properties of coarse grained soil under high stress. This project employs the self-developed inter-particle contact testing apparatus and micro visualization system into an investigation on the contact mechanics properties and rheological properties of coarse grained soil with a combination of macro and microscopic methods. (1)Through contacts and rheological test, intergranular contact model and rheological model of the coarse grained soil are established. Discrete element numerical simulation would be used to disclose the connection between macro and microscopic mechanics. (2) A visual large direct shear test would be used to reveal the grain crushing evolution and macro-microscopic mechanics mechanism of the coarse grained soil. (3)Through visual centrifuge test and the discrete element numerical simulation, the intergranular contact model and rheological model would be verified, as well as analyzing the inner link between the microscopic mechanics and macroscopic mechanical response of the coarse grained soil. (4) Based on the measured data, discrete and continuous hybrid numerical method would be employed to analyze the weakness of coarse grained soil dam, which would reveal the mechanical mechanism of super-high dam during the failure process. This research would provide microscopic mechanics foundation for the further research of coarse grained soil under high stress, which provides theory basis for analysis and evaluation about the performance of super-high dam.

近年我国超高坝建设发展较快，对在髙应力下粗粒土力学和坝工特性的研究引起较多学者的关注。本项目拟采用自主研发的试验装置及可视化细观测试分析系统，利用多种试验手段和数值模拟，从细观层面入手、细宏观相结合来研究在髙应力作用下粗粒土细观力学及坝工特性：(1)通过粒间接触和流变试验，建立髙应力下粒间接触模型和流变模型，结合离散元数值模拟揭示粒间接触细宏观力学之间的联系；(2)通过可视大型直剪试验，揭示粗粒土的颗粒破碎演化规律和细观力学机理；(3)通过可视离心机试验，验证粒间接触模型和流变模型，揭示接近实际应力场条件下粗粒土破坏的细观力学机理及与宏观力学响应之间的内在联系；(4)结合实际工程，采用离散-连续混合数值方法，分析超高土石坝结构薄弱环节的细观演化规律，从细观角度揭示超高土石坝破坏过程的力学机理。本研究可为髙应力下粗粒土的深入研究提供细观力学基础，为超高土石坝工程性能的分析和评价提供理论依据。

近年我国超高坝建设发展较快，对在髙应力下粗粒土力学和坝工特性的研究引起较多学者的关注。本项目在课题组前期研究的基础上，利用自主研发的试验装置及可视化细观测试分析系统，进行了室内高应力颗粒接触试验和离心机模型试验，并结合离散元数值模拟，从细观层面入手、细宏观相结合系统研究了在髙应力作用下粗粒土细观力学及坝工特性。. 通过粒间接触和流变试验，揭示了粗粒土颗粒接触特性的力学机理，发现板岩和石膏的法向接触刚度值相差4倍，球-面接触试验的法向接触刚度是球-球接触试验的法向接触刚度的1.7倍。建立了弹性核尺寸与球形颗粒材料力学性质和颗粒尺寸相关的经验公式。建立了球形颗粒球-球法向接触破碎准则和石膏颗粒三点接触下颗粒破碎强度准则。建立了髙应力下粒间接触模型和流变模型，结合离散元数值模拟揭示了粒间接触细宏观力学之间的联系，实现了对颗粒内部破碎的细观过程和弹性核发展过程的观测。. 通过可视大型直剪试验，揭示了粗粒土的颗粒破碎演化规律和细观力学机理。通过对大型直剪数值试验中颗粒的细观运动规律进行分析发现，在剪切过程中剪切带的形成与发展并不是严格按照上下盒之间的剪切缝展开，而是沿着向上突起的拱形滑动面发展。.通过可视离心机试验，验证了粒间接触模型和流变模型，揭示了接近实际应力场条件下粗粒土破坏的细观力学机理及与宏观力学响应之间的内在联系。通过对不同粒径大小的粗粒土坝体，在不同离心加速度下进行模型试验，发现离心加速度对于粗粒土的粒径具有明显的放大作用。. 本课题从粗粒土颗粒接触角度研究颗粒破碎的力学机理，开辟了研究粗粒土颗粒破碎的新途径，不仅为髙应力下粗粒土的深入研究提供了细观力学基础，也为超高土石坝工程性能的分析提供理论依据。本项目组已获得国家实用新型专利一项，发表学术论文9篇，其中SCI、EI论文8篇。