青藏高原多年冻土区单桩受斜坡地基土原位冻胀影响下的力学特性研究

Study on the Mechanical Properties of Single Pile under the Influence of In-situ Frost Heave of Slope Foundation Soil in Permafrost Region of Qinghai-Tibet Plateau

在青藏高原多年冻土区铁路建设中,由于高原山区地形地貌复杂,建设在斜坡中的桩基础不在少数,地基土经历冻融过程以后桩基常常发生倾斜,严重影响铁路运行安全。为揭示在地基冻胀影响下多年冻土区斜坡单桩的倾斜机理,基于传热学与弹性力学,建立桩体体系热力耦合计算模型并进行室内试验验证计算模型的合理性,考虑地基土原位冻胀、水分相变、大气变暖等因素,进行地基土冻胀影响下斜坡桩基力学特性模拟分析。研究表明:斜坡桩体在地基土冻胀过程受到不均匀水平冻胀力、产生水平位移以及桩体弯矩,且水平位移随着地基斜坡坡度增大而增大;因不均匀水平冻胀引起的桩体应力占总应力的46.3%,对桩体安全性以及工程寿命产生较大影响。进行受到斜坡地基土冻胀影响下单桩力学特性分析,揭示在地基冻胀影响下多年冻土区斜坡单桩的倾斜机理,对多年冻土区斜坡桩基设计及运营有一定的参考价值。

In the railway construction within the permafrost region of the Qinghai-Tibet Plateau,due to the complex topography of the plateau mountainous area,there are many pile foundations built in the slope.After undergoing the freeze-thaw process,the soil foundation often causes the pile foundation to tilt,seriously affecting the safety of railway operations.In order to reveal the inclination mechanism of single pile on slope in permafrost area under the influence of foundation frost heaving,based on heat transfer and elastic mechanics,this paper establishes a thermal-mechanical coupling calculation model of pile system and carries out indoor test to verify the rationality of the calculation model.Considering the factors of in-situ frost heaving of foundation soil,water phase change and atmospheric warming,the mechanical characteristics of slope pile foundation under the influence of frost heaving of foundation soil are simulated and analyzed.The research shows that the slope pile is subjected to uneven horizontal frost heave force,horizontal displacement and pile bending moment in the process of foundation soil frost heave,and the horizontal displacement increases with the increase of foundation slope gradient.The pile stress caused by uneven horizontal frost heave accounts for 46.3%of the total stress,which has a great influence on the safety and engineering life of the pile.In this paper,the mechanical properties of single pile under the influence of frost heave of slope foundation soil are analyzed,and the inclination mechanism of single pile under the influence of frost heave of foundation soil is revealed,which could provide some reference for the design and operation of slope pile foundation in permafrost area.