均质砂土中高喷插芯组合桩多界面剪切特性对比试验研究

doi:10.13722/j.cnki.jrme.2021.0315

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摘要采用大型桩基模型试验加载系统，砂雨法施工，对4种不同组合形式(上组合、下组合、分段组合I、分段组合II)的高喷插芯组合桩(简称JPP桩)进行抗压与抗拔承载性能对比模型试验研究，并对不同组合形式的JPP桩进行界面剪切试验研究，分析桩与桩周土、芯桩与水泥土界面剪切规律。研究结果表明：(1) 不同组合形式对承载力有较大影响，抗压试验中分段组合II的极限承载力最高，抗拔试验中下组合抗拔承载能力最高，可见JPP桩实际工程设计时宜分段组合，且组合段宜放在桩体的中下部。(2) 抗拔极限承载力为抗压极限承载力的10%～15%，抗拔荷载下的平均侧摩阻力为抗压下的13%～20%。(3) 抗压与抗拔荷载下的桩侧摩阻力随桩土相对位移的增加而逐渐变大，均呈现出双曲线分布；抗拔荷载下的桩侧摩阻力达到极限值时所需要的位移约2 mm，抗压荷载下的桩侧摩阻力达到极限值时所需要的位移约7 mm。(4) 芯桩与水泥土界面剪切，加载初期，在很小的相对位移下界面摩阻力迅速增加，界面剪切刚度趋于无穷大；随着荷载的增加，界面剪切刚度变小，相对位移增大，进入弹性工作阶段；随着荷载的进一步增加，界面摩阻力增长又加快，并很快达到剪切破坏。(5) 抗压、抗拔荷载下芯桩与水泥土界面剪切刚度约为水泥土与桩周土界面剪切刚度的400，200倍，从而保证芯桩与水泥土协同工作，达到扩大直径、提高承载力的目的。

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	任连伟1
	吕陈陈1
	王新宇1
	顿志林1
	王俊林2

关键词 ：桩基工程, 组合桩, 桩&ndash, 土相互作用, 多界面剪切, 模型试验, 抗压与抗拔

Abstract：Comparative model tests on the bearing capacity and the multi-interface performance of jet grouting soil-cement-pile strengthened piles(JPP) with four different combinations(upper，lower，segment-Ι and segment-II) under compressive and uplift loads were carried out based on large-scale pile foundation load test equipment system. Model piles were buried by sand pour method. Model test results show that：(1) The bearing capacity of JPP piles is affected greatly by combination forms. Particularly，the segment-II combination can achieve the maximum bearing capacity in compressive load test while the lower combination can achieve the maximum value in uplift load test，indicating that JPPs should be segmented and the soil-cement segment should be placed in the lower of JPP piles in the engineering design. (2) The uplift bearing capacity is about 10%–15% of the compressive bearing capacity，and the average side resistance under uplifting load is approximately 13%–20% that under compressive load. (3) The side resistance of JPPs under both compressive and uplift loads increases with increasing the relative displacement between pile and soil in a hyperbolic form. The relative displacements necessary for the side resistance of JPPs reaching the limit value are around 2 and 7 mm under compressive and uplift loads，respectively. (4) At the initial stage of loading，the interface friction increases rapidly with a small relative displacement between core pile and soil-cement，and the interface shear stiffness tends to infinity. With increasing the load，the interface shear stiffness decreases while the relative displacement increases，showing a flexible work stage. As the load increases further，the interface friction increases faster and soon reaches the shear failure. (5) The interface shear stiffness between core pile and soil-cement under compressive and uplift loads is about 400 and 200 times that between cement-soil and soil around JPP，respectively，which ensures that core pile and cement-soil can work together to enlarge the diameter and to increase the bearing capacity.

Key words： foundation engineering composite pile pile-soil interaction multi-interface shear model tests compressive and uplifting load

引用本文:

任连伟1，吕陈陈1，王新宇1，顿志林1，王俊林2. 均质砂土中高喷插芯组合桩多界面剪切特性对比试验研究[J]. 岩石力学与工程学报, 2022, 41(4): 822-835.
REN Lianwei1，LV Chenchen1，WANG Xinyu1，DUN Zhilin1，WANG Junlin2. Model tests on multi-interface shear performance of jet grouting soil-cement-pile strengthened piles in homogeneous sand. , 2022, 41(4): 822-835.

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http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2021.0315 或 http://rockmech.whrsm.ac.cn/CN/Y2022/V41/I4/822

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