劲性复合桩挤土效应及承载力作用机制研究

Soil squeezing effect and bearing mechanism of strength composite pile

劲性复合桩施工工艺复杂,为了明晰其成桩过程中的挤土效应及荷载传递机制,开展了劲性复合桩挤土效应试验、静力触探试验研究,描述了劲性复合桩成桩过程中桩周土体孔隙水压力、总应力、有效应力的变化情况,探讨了劲性复合桩承载力形成机制。试验结果表明:劲性复合桩挤土效应沿桩径方向逐渐减小,沿桩长方向逐渐增大;在劲性复合桩成桩过程中,周围土层的有效应力增长了12%~63%,桩侧摩阻力也因此显著提升;锥尖阻力、侧壁阻力则分别提高了13%~84%、8%~97%。同时,劲性复合桩通过多种不同强度材料的组合,沿桩径方向依次形成了承载力递减的4个受力构件,实现了比常规桩基均质材料更好的承载效能,本质上是契合了桩顶荷载沿桩径方向、桩长方向引起的桩身剪切应力、压缩应力均会逐渐衰减的特性,这也是劲性复合桩显著经济优势的来源。

The construction technology of strength composite pile is very complex.In order to understand the soil squeezing effect and load transfer mechanism in the piling process,the soil compaction effect test and static cone penetration test of strength composite pile were conducted,and the changes of pore water pressure,total stress and effective stress of soil around the strength composite pile were studied.The test results showed that the soil squeezing effect of strength composite pile decreased gradually along the diameter and increased gradually along the length.In the piling process,the effective stress of the surrounding soil layer increased by 12%−63%,and the side friction resistance of pile increased significantly.The tip resistance and side resistance increased by about 13%−84%and 8%−97%,respectively.Additionally,four load-bearing members with decreasing bearing capacity were formed along the pile diameter through the combination of a variety of strength materials,which realized a better bearing efficiency than that of conventional piles with homogeneous materials.It is consistent with the characteristics that the shear stress and compressive stress of piles caused by the pile top load along the diameter direction and length direction will gradually decay,which is also the source of the significant economic advantage of the strength composite pile.