反复荷载作用下软土地基长期沉降机理研究

In recent years, with the development of grain logistics construction, civil engineers often encounter cyclic deformation of soft clay due to the application of repeated loading. The demands for deformation control of soft clay foundation about the silos and oil tanks are becoming higher and higher. At the same time the foundation of container terminal and yard also often subject to long-term repeated loading. Because the consolidation theory of soft clay is drop behind the engineering practice, the accumulation settlement and deformation of soft clay foundation caused by the long-term repeated loading has become a very outstanding question. The researcher would study the settlement mechanism of soft clay of zhengzhou and other places under long term repeated loading relying on the key projects of China's grain circulation construction. In term of the specialty of the repeated loading, the technique route of this research includes several kinds of method or means, general analytic method and numerical method or test and field monitoring to solve deformation mechanism problems of soft clay. The chief content of this research mainly includes development of low frequency repeated loading system, constitutive model analysis about the primary consolidation and secondary consolidation deformation of soft clay soil under long term repeated loading based on the results of laboratory test and field data. In this research, we hope develop a theoretical model of soft clay foundation under repeated loading through exploring the relationship of the releasing of water in the consolidation and macroscopically accumulation deformation of soft clay, and put forward a set of soft clay foundation deformation calculation method that can reflect the relatively characteristic of the long time low frequency repeated loading. This research results not only could improve the design theory of soft soil foundation, realize the development of soil mechanics, but also for Henan province, and furthermore, spread all over the whole China's grain logistics facilities construction and operation safety have very important guidance significance to practical engineering.

近年来，随着粮食物流建设的迅猛发展，对筒仓、油罐等地基变形的控制要求越来越高。同时在集装箱码头、堆场等地也存在长期反复荷载的作用。由于软土固结理论落后于工程实践的发展，使得长期低频反复荷载引起的软土地基累积沉降问题日益突出。本项目将依托中国粮食流通建设项目重点工程，拟以郑州等地软土为研究对象，考虑其所受荷载的特殊性，从土体固结释水角度出发，综合运用室内土工试验、理论分析、数值模拟以及现场监测等技术手段，探究软土释水固结与反复变形等宏观行为下的微观机理与内在联系，揭示长期低频反复荷载作用下饱和软土地基的固结流变特性与变形规律，建立理论分析模型，并提出一套能够较为真实地反映长期低频反复荷载下饱和软土地基沉降的计算方法。通过本项目的实施，不仅可以完善该类软土地基的设计理论，实现土力学的发展，而且对于河南乃至我国粮食物流设施建设及其运营安全具有十分重要的工程指导意义。

长期低频反复荷载引起的软土地基累积沉降问题日益突出。本项目依托中国粮食流通建设项目重点工程，以郑州等地软土为研究对象，考虑其所受荷载的特殊性，综合运用室内土工试验、理论分析、数值模拟以及现场监测等技术手段，揭示了长期低频反复荷载作用下饱和软土地基的固结变形规律。通过研制室内低频反复荷载试验装置，结合改装的渗透固结仪器，研究了不同加载频率下软土的变形机制。基于梯形反复荷载周期偶函数的傅里叶级数之上，对其余弦函数半幅展开，取半幅函数的偶延拓，得到广义梯形反复荷载周期波的傅里叶级数展开形式。按照实际荷载的类型与参数赋予级数式中的变量值，就可以得到相应的反复荷载形式，从而代入固结方程求解。有利于编程与数值计算，提高了相关研究的工作效率。基于修正剑桥模型，利用有限元软件，对低频周期荷载作用下仓储设施地基的固结沉降特点进行了理论分析，提出了反映长期低频反复荷载下饱和软土地基沉降的计算方法。研究成果对于河南乃至我国粮食物流设施建设及其运营安全具有十分重要的工程指导意义。