砾卵石层中桩底灌浆钻孔灌注桩承载性质研究*

  从泥浆护壁钻孔灌注桩施工及承载过程中存在的问题出发。依据现场试验结果，探讨了桩底持力层为砾卵石层时桩底灌浆钻孔灌注桩的承载特性。指出桩底持力层为砾卵石层中长径比为54.1～57.1的中长桩时，桩底灌浆钻孔灌注桩的桩侧阻较常规桩提高2倍，桩的沉降量大幅度减小，桩端阻存在滞后反应。此外桩底灌浆钻孔灌注桩在承载过程中主要以弹性变形为主，残余变形很小。所得结论来源于现场试验结果，对工程实践能够起到指导的作用。

STUDY ON BEHAVIOR OF BORED PILES WITH GROUTED-BASE ON GRAVEL STRATUM

Slurry drilling method is widely employed in pile construction. Sediments at base and clay slurry along hole shaft cannot be avoided in construction procedure with this method. Engineering practice proves that base sediments and slurry can severely reduce the pile’s bearing capacity and increase the settlement of the bored cast-in–situ piles. Based on the results of the field experiments，the bearing features of cast-in-situ bored piles with grouted toe in gravel bearing stratum are analysed. It is pointed out that the friction of cast-in-situ bored piles (lenth/diameter ratio of 54.1～57.1) with grouted toe in gravel bearing stratum is three times of that of the commom bored piles. The settlement of the bored cast-in-situ piles with grouted toe can be largely decreased. Most of deformation of bored cast-in-situ piles with grouted toe is elastic，and residual deformation is quite small. The experiment results can give some references to pile construction and design.