岛礁机场跑道压实钙质砂路基安定性机理及长期累积变形模型研究

The airfield is a siginificant infrastructure which is necessary for the development and construction of coral reefs in South China Sea, and the post-construction settlement of subgrade with compacted calcareous sand under its runway is critical for the regular operation of airfield in the coral reefs. So far, there is not yet a suitable model to make a resonable description of the long-term cumulative deformation behavior of compacted calcareous sand. A substantial amount of evidence in literature shows that to get a comprehensive knowledge of inherent mechanism of cumulative deformation of calcareous sand, it is necessary to thoroughly investigate particle crushing of calcareous sand under repeated loads of airplane’s passage. The investigation will be carried out from the macroscopic and mesoscopic scales in this project by means of the laboratory test, theoretical investigation and numerical simulation. At first, the evolution of particle crushing, shakedown mechanism and cumulative deformation of calcareous sand will be investigated through a series of laboratory tests. And next, an analysis method of shakedown limit, a cyclic deterioration model and its quick integration strategy for calcareous sand will be constituted by using some theoretical analysis of the test results, and meanwhile a prediction approach and its calculation program for the cumulative deformation of subgrade with compacted calcareous sand will also be developed and incorporated into ABAQUS software. At last, the abovementioned prediction approach will be verified by some experimental evidence and measured results in the field. A large number of numerical simulations will be conducted to explore the essential link between particle crushing of calcareous sand and evolution of stress and deformation of subgrade with compacted calcareous sand (or inter-particle’s contact force and displacement) with time-spatial variation in the operation period of airfield runway in the coral reefs. The research findings in this project can present theoretical and technical supports to resolve some troublesome problems, such as the optimization of construction technology, prediction of long term cumulative deformation and evaluation of safe operation of subgrade with compacted calcareous sand under the airfield runway in the coral reefs.

机场是南海岛礁开发建设所需的重大基础设施，而其跑道压实钙质砂路基工后沉降大小是岛礁机场能否正常运营的关键。迄今为止，尚未有模型能够合理地描述钙质砂的长期累积变形行为。研究表明：若不从细观层面深入研究钙质砂的颗粒破碎行为就无法透彻了解其累积变形的内在机理。为此，本项目联合室内试验、理论分析和数值模拟手段，从宏、细观两尺度开展相关研究：基于室内试验研究钙质砂颗粒破碎、安定性机理和累积变形规律，基于理论分析构建钙质砂的安定性分析方法和循环劣化模型以及快速积分算法，同时研发长期累积变形预测方法并嵌入ABAQUS软件。该方法经验证后用于实体工程模拟，全面探讨岛礁机场跑道运营期钙质砂路基的应力/变形（或颗粒接触力/位移）时空演化规律及其与钙质砂颗粒破碎的本质联系。研究成果可为珊瑚岛礁机场跑道压实钙质砂路基的施工工艺优化、长期累积变形预测和运行安全评估等关键问题提供理论支撑与技术支持。

机场跑道是南海岛礁开发建设所需重大基础设施，而跑道下路基压实钙质砂在飞机荷载下长期累积沉降量的大小是岛礁机场能否正常运营的关键。本项目采用试验研究、理论分析和数值模拟相结合的方法，从宏/细观两个层面开展压实钙质砂路基长期累积变形特性研究。通过各类试验，分析获得了飞机荷载下钙质砂颗粒破碎与路基累积变形规律及二者的内在联系；基于理论分析，构建了钙质砂广义塑性模型及长期累积变形预测简化算法；通过数值模拟，分析获得了飞机荷载下压实钙质砂路基动应力与长期累积变形演化规律，并与试验结果和简化算法预测结果进行了对比分析；基于机理分析，揭示了岛礁机场跑道压实钙质砂路基安定性及长期累积变形宏细观机理。研究成果丰富了特殊土工程性质研究内涵，在规范化处理后即可用于解决岛礁机场跑道压实钙质砂路基施工工艺优化、长期累积变形预测和运行安全评估等工程技术问题。