季节冻土区扩底单桩受力性能研究进展与展望

在深季节冻土区， 正冻土和桩相互作用时可能会导致桩基的拔断或整体冻拔破坏。在桩周土冻胀过程中， 等截面直桩主要通过桩和未冻区融土间的摩阻力达到锚固效果。而对于端部直径大于桩身直径的扩底桩来说， 当桩基有整体上拔的趋势时， 扩大头会受到上覆土层的阻力而起到锚固/抗冻拔作用。通过回顾国内外研究文献， 介绍了扩底抗拔桩现有的工程背景及应用情况， 并对季节冻土区桩基的受力性能进行了总结和分析， 主要内容包括： 土体冻胀和桩基的相互作用研究， 切向冻胀力试验研究和理论研究， 切向冻胀力作用下扩底桩基冻胀反力试验研究及理论研究， 切向冻胀力作用下未冻区桩-融土间摩阻力的研究概况等。最后， 结合现有的研究内容， 对季节冻土区扩底桩的应用及研究提出进一步的展望。

Study of mechanical behaviors of pile foundation with enlarged end in seasonally frozen ground regions： progress and review

In deep seasonally frozen ground regions， the interaction between freezing soil and pile may cause frost jacking or failure of pile. In the process of frost heave of soil surrounding the pile， the anchoring effect is mainly carried out through the frictional resistance of pile-thawing soil interface for a uniform-section pile. However， for a pile with enlarged end， whose base diameter is larger than its shaft diameter， will be subjected to the resistance of the overlying soil and play a role of anchoring or anti-frost jacking characteristic when the pile is tend to be pull up. By reviewing the domestic and foreign research literature， the paper briefly introduces the existing engineering background and application of the pile with enlarged end，and summarizes and analyses the mechanical properties of the pile foundation in the deep seasonally frozen ground regions. The main contents include the interaction between frost heave of soil and pile foundation， the experimental and theoretical research on tangential frost heave force， and the experimental and theoretical research on counter-frost heave force of pile foundation with enlarged end， and frictional resistance between pile and thawed soil under the action of tangential frost heave force， etc. In the end， the application and research of the pile foundation with enlarged end in the seasonal frozen ground regions are further prospected.