钻孔灌注桩成孔孔径变化及其卸荷效应机理研究

The Research on the Mechanism of Variation on Diameter of Cavities of Cast-In-Place Bored Piles and Its' Unloading Effect

针对钻孔灌注桩钻孔的卸荷效应及孔周土体的粘弹性,分析了孔壁受力变化的机理。结合实际工程成孔检测的数据,分析钻孔卸荷条件下,孔径随时间及深度的变化规律和特性。并针对不同类型的钻孔机具进行分析对比。考虑钻孔卸荷时孔周土体流变特性,以标准线性固体模型中的推广Kelvin体为桩周土的流变模型,推导钻孔卸荷后,孔壁水平应力和位移随时间的变化的公式,对深入研究钻孔的流变特性和卸荷效应对桩体承载机理的影响具有重要意义。

The paper analyzes the mechanism of the variation of load enforced on cavities based on the unloading effect of cast- in-place bored piles and the viscoelastic property of soil around piles. Meanwhile, the variation rule of the diameter of cavities with depth, as well as time, is analyzed under the unloading effect caused by boring, making use of measured data about the diameter of cavities in engineering spot, and then the contrast can be made in allusion to the use of pile drivers of different types. Otherwise, the formula of horizontal geostress and displacement of cavities with time is derived based on H-K rheological model of the soil around piles under the unloading effect, considering the property of relaxation and creep of soil, which has significant meaning to the further study of creep effect of cavities and the influence of the unloading effect on the bearing mechanism of cast-in-place bored piles.