静压群桩挤土效应的关键问题和机理研究

在我国大规模开展的城市工程活动中，静力压桩（静压桩）由于其经济高效、噪音小、污染小等诸多优点获得了日益广泛的应用，该领域也是近年来科学研究的热点。虽然静压单桩挤土效应的相关研究已相当深入，但群桩的沉桩挤土机理迄今为止尚未明确，特别是群桩沉桩的数值仿真模拟研究非常匮乏。申请人在早期的研究中已初步开发了采用有效应力计算框架、具有流固耦合计算能力的大变形有限元计算技术-“混合欧拉-拉格朗日”有限元。本项目拟完善和采用该技术开展群桩沉桩的数值仿真模拟，同时结合新型透明土试验和大比尺模型试验，开展群桩挤土效应综合分析。项目将重点分析群桩挤土效应的三个关键问题-桩体上浮，桩塞，桩侧负摩阻力。通过数值仿真模拟和模型试验分析揭示上述关键问题的作用机理，建立相关的科学计算方法，提出有效的防治措施。研究成果将完善静压桩设计与计算理论，为优化静压桩的设计、施工提供科学依据，具有重要的应用价值。

Due to its high efficiency, low noise and low pollution, the jacked pile is being widely used in a large number of construction projects of China. It is also a subject of much research popularity. Although research on the installation process of the single jacked pile, and the squeezing effect on the soil during installation, is fairly thorough, the governing mechanism involved in the pile group installation remain, at least partially, unclear. There is, in particular, a lack of reliable numerical analysis results. In the prior study of applicant, a hybrid Eulerian-Lagrangian finite element method has been preliminarily developed, which can undertake the large-deformation, pore pressure coupled analysis because of its adoption of the effective stress calculation framework. This project intends to refine and utilize this technique to carry out the three dimensional large deformation finite element simulation of pile group installation, which, combined with the transparent soil tests and large-scale model tests, serve to grasp an in-depth understanding of the squeezing effect of pile group installation on the soil. The particular emphasis of this research is placed on addressing three key problems, namely pile heave, pile derivability degradation, and negative skin friction. Research aims to explore the fundamental mechanism of these problems, propose the relevant scientific calculation methods and establish the effective mitigation approaches. The research results will be helpful in improving the design and calculation theories of jacked pile group, providing scientific basis to optimize its design and construction. It is expected to have important practical implication.