桩端桩侧后注浆钻孔灌注桩承载性能试验研究

Experimental Study on Bearing Capacity of Bored Piles Using Pile Tip and Side Post-grouting Technology

从钻孔灌注桩竖向承载机理及其承载能力影响因素出发,考虑桩端桩侧复式后注浆施工对钻孔灌注桩端土层和桩侧泥皮的加固效应,初步探讨了郑州地区复式后注浆钻孔灌注桩的承载能力和变形特性,通过郑州某工程复式后注浆钻孔灌注桩现场足尺寸静载荷试验,研究了后注浆对钻孔灌注桩桩端阻力、桩侧摩阻力的提高效应,对桩端桩侧荷载分担比以及对沉降变形和整体竖向承载力的影响等。结果表明:桩侧注浆很好地改善了桩土界面力学能质,使侧阻力得到有效发挥;桩端注浆使沉渣层等桩端土层得以加固,桩端阻力提前发挥;复式注浆作用使桩土界面塑性位移减小,桩顶沉降变缓,灌注桩承载能力得到明显提高。

In view of the vertical bearing mechanism of bored cast-in-place piles and the influencing factors of their bearing capacity, considering the reinforcement effect on pile tip soil and pile side mud cake by compound post-grouting at pile tip and side, the bearing capacity and deformation property of compound post- grouted bored piles in Zhengzhou area are preliminary discussed. By full-scale static loading test on the post- grouted bored piles of a project in Zhengzhou, the improving effect of pile tip resistance and pile side frictional resistance, the load share of pile tip and side by composite post-grouting, and its influence on settlement deformation as well as the whole vertical bearing capacity are researched. The results show that （1） grouting at pile side has improved the mechanical property of interface between pile and soil, which made the resistance of pile side play effectively ; （2） grouting at pile tip has reinforced soil layer of pile tip such as sediment layer, which made the resistance of pile tip play in advance; （3） compound grouting has decreased the plastic displacement of interface between pile and soil, which made pile tip settlement slowly and obviously improved the bearing capacity of bored piles.