托换桩钻孔施工对既有受荷桩承载机理的影响研究

Study on the Influence of Underpinning Pile Drilling Construction on the Bearing Mechanism of Existing Loaded Pile

托换桩与既有受荷桩之间距离较小,从而导致托换桩钻孔施工过程可能对既有受荷桩承载机理带来一定的影响。以浙江饭店地下车库翻修扩建工程为背景,通过Mindlin原理及Hoek-Brown破坏准则分析了托换桩钻孔施工过程对既有受荷桩桩侧及桩端阻力发挥机理。得出:在上部土层中,既有桩桩侧摩阻力随着钻孔直径的增大而缓慢降低,随着钻孔数量的增加而降低;在下部土层中,既有桩桩侧摩阻力随着钻孔直径的增大而缓慢增大,随着钻孔数量的增加而增加;在托换桩钻孔端部一定范围内,既有桩桩侧将出现负摩阻力;桩孔间距对既有桩桩侧摩阻力的影响可忽略不计;托换桩钻孔数量,钻孔深度,钻孔直径及间距对既有桩桩端阻力的影响可忽略不计。

The drilling construction may have some certain impact on the bearing mechanism of the existing loaded pile, due to their distance is small. This paper analyzes mechanism of the skin and end resistance of the existing loaded pile during the drilling construction of underpinning pile by using Mindlin principle and Hoek-Brown failure criterion, based on the Zhejiang Hotel Expansion Project. The result shows: in the upper soil layer, the skin friction of existing pile decreases slowly with the increase of borehole diameter and decreases with the increase of borehole number;In the lower soil layer, the skin friction of existing pile increases slowly with the increase of borehole diameter and the number of boreholes;the negative friction of existing pile will appear on the end of underpinning pile, side of existing pile;the influence of space on the skin friction of existing pile can be ignored;the influence of the number, depth, diameter and space on the end resistance of the existing pile can be ignored.