LOAD-TRANSFER LAWS OF A SINGLE PILE AND DETERMINATION OF REASONABLE POSITIONS FOR GROUTING ON PILE SIDES
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摘要: 为研究不同加载点及不同加载方向对单桩荷载传递特性的影响,进行了相同条件下的桩端无土顶压桩、桩端有土顶压桩和底托桩的室内模型试验,得到了不同加载方式下桩身轴力、桩侧摩阻力等分布规律。研究结果表明:达到负摩阻力极限值所需要的桩土相对位移比正摩阻力的小,不同加载位置显著影响桩侧摩阻力的分布形式,桩侧摩阻力最大值出现在距离加载点1/3桩长处。对于承受竖向荷载的抗压桩,应充分利用好中上部地层,对承受竖向抗拔荷载的底托桩,应充分利用好中下部地层。为提高单桩竖向承载力进行桩侧注浆时,对于抗压桩,注浆位置宜取在桩的中上部分,而对于底托抗拔桩,注浆位置则宜取在桩的中下部分。Abstract: To study the influence of different loading points and different loading directions on the load transfer characteristics of a single pile, model tests of the axial compressive piles without or with soil at pile tips and bottom-lifted piles in the same conditions were conducted. Then the laws of axial forces and side friction in different loading modes were obtained. The results showed that the relative limit displacement between piles and soil required for negative frictional resistance was smaller than that of positive frictional resistance. Loading positions significantly influenced on the evoluation of pile side friction, and the maximum of the pile side friction appeared at the one-third length of piles away from the loading point. For axial compressive piles, the middle and upper strata should be fully utilized; and for bottom-lifted piles, the middle and lower strata should be fully utilized. When grouting was inplemented on the sides of piles to improve the vertical bearing capacity, the grouting positions beside the upper and middle parts of pile shafts for axial compressive piles and beside the middle and lower parts of the pile shafts for the bottom-lifted piles should be considered.
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Key words:
- axial compressive pile /
- bottom-lifted pile /
- side friction of pile /
- load transfer /
- grouting position
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