大直径随钻跟管桩竖向抗压承载性能试验研究

随钻跟管桩是一种桩侧后注浆的非挤土PHC管桩桩型，是近年研发出的新型大直径桩基础。为了研究这种新桩型的竖向抗压承载性能，对现场5根直径1m的随钻跟管桩进行静载和高应变承载力试验。研究结果表明：以静载试验结果为校核标准，高应变承载力检测误差可控制在±10%以内；嵌岩0.5m的随钻跟管桩极限承载力可达到20000kN，比同等直径泥浆护壁灌注桩的承载力经验计算值大13%～23%；桩侧后注浆工艺和桩端嵌岩深度能有效提高随钻跟管桩的侧阻力发挥，实测值比灌注桩的规范计算值大28%以上；虽然现场4根随钻跟管桩均嵌入中风化花岗岩0.5m，但端阻比小于30%，呈现摩擦型桩的承载性状。试验成果有助于进一步揭示随钻跟管桩的竖向抗压承载机理，可为其工程设计与工艺优化提供依据。

Vertical bearing capacity characteristics of large-diameter DPC pipe piles based on field tests

The drilling with pre-stressed concrete (DPC) pipe pile is a large-diameter and non-soil-squeezing PHC pipe pile with pile shaft grouting, which is a new type of pile foundation developed in recent years. To study the vertical compressive bearing capacity of the new type of pipe, the static load and high-strain dynamic field tests on five DPC pipe piles with a diameter of 1m are carried out. The field test results show that the high-strain dynamic test can be used for detecting the bearing capacities of pile foundations, and its testing error is within 10%. The vertical ultimate bearing capacities of four DPC pipe piles embedded in rock strata with a depth of 0.5m may reach 20000kN, which shall be 13%～23% larger than those empirical values predicted from the slurry protected cast-in-place pile of the same diameter. The pile shaft grouting and rock-socketed/embedment depth of pile can effectively improve the shaft friction resistance of DPC pipe piles, and the measured value are more than 28% larger than the recommended value calculated from the Code of pile foundation for slurry protected cast-in-place piles. Although all the four piles are embedded into the moderately weathered rock about 0.5m, the tip resistance ratios are less than 30%, exhibiting the bearing behavior of friction-type piles. Based on the field test results, the vertical bearing mechanism of DPC pipe piles can be revealed, which shall be beneficial to the design and optimization of DPC pipe piles. 