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桥梁桩基工程施工由于影响因素较多,断桩事故时有发生。为研究黄泛区大直径超长桩的承载性状及侧摩阻力发挥性能,对黄泛区桥梁超长钻孔灌注桩进行单桩静载试验,并与断桩处理后试验结果进行对比。结果表明:黄泛区xh1#试桩与处理后xh2#试桩声测结果符合Ⅰ类桩的相关要求,Q-s曲线均呈缓变型,变化规律基本类似;在相同地层条件下,断桩处理后承载力较xh1#试桩有所增大,说明采用桩芯凿井法处理断桩方案可靠有效。当桩顶施加荷载较小时,桩顶荷载完全由桩侧摩阻力承担。在极限荷载作用下,桩端阻力承担10%左右的桩顶荷载,这与中短桩明显不同。除表层粉土外,试桩所得极限侧摩阻力大于规范推荐值,反映出黄泛区桩基具有较高的承载能力。2根试桩侧摩阻力变化规律类似,说明桩芯凿井法施工对桩周土影响较小,符合试桩工程相关要求。利用现行规范进行超长桩承载力计算,其结果与静载试验结果相差较大,建议黄泛区桩基设计宜将规范侧摩阻力建议值进行一定的修正。
Bridge pile foundation construction due to many factors, broken pile accidents have occurred. In order to study the bearing properties and lateral frictional resistance performance of large-diameter super-long piles in the Yellow River, the static load test of single-piles of ultra-long bored piles in the Yellow River and compared with the experimental results after broken piles. The results show that the sounding results of xh1 # test pile and xh2 # test pile in the flood plain area are in accordance with the relevant requirements of pile type Ⅰ. The Qs curves show a gradual changing pattern and the variation law is basically similar. Under the same strata condition, Bearing capacity than xh1 # test pile has increased, indicating the use of pile core sinking method to deal with broken pile is reliable and effective. When the top load is small, the load on the top of the pile is completely absorbed by the friction on the pile side. Under the action of ultimate load, the pile end resistance takes about 10% of the pile top load, which is obviously different from that of medium and short piles. Except for the surface silt, the ultimate lateral friction obtained from the test pile is greater than the recommended value of the specification, which indicates that the pile foundation in the Huanghe River has a high carrying capacity. The variation of side friction resistance of two test piles is similar, which shows that the construction of pile core pounding has less influence on the soil around the piles, which accords with the relevant requirements of test piling project. The calculation of the bearing capacity of the extra-long piles using the current codes is quite different from the results of the static load tests. It is suggested that the recommended values of the normalized frictional resistance should be modified to some extent in the design of the pile foundation in the Huanghe River.