苏州地区大直径超长后注浆钻孔灌注桩试验研究

大直径超长后注浆钻孔灌注桩单桩合理注浆量和极限承载力的确定成为设计所面临的问题。介绍了后注浆钻孔灌注桩后注浆的加固机理和注浆方式。着重介绍了苏州中心广场项目不同桩径、不同持力层的大直径超长后注浆钻孔灌注桩的试桩数据,并结合苏州金鸡湖周边其他4个超高层项目大直径超长后注浆钻孔灌注桩的试验数据,分析了大直径超长后注浆钻孔灌注桩的承载性能。根据《建筑桩基技术规范》(JGJ 94—2008)和上海市《地基基础设计规范》(DGJ 08-11—2010)中的相关公式,估算了单桩注浆量和单桩极限承载力标准值,并将其估算结果与试验数据进行对比,给出了苏州地区类似地质条件下直径1000mm大直径超长后注浆钻孔灌注桩桩端后注浆量的合理范围为2～4t的建议,提出了大直径超长后注浆钻孔灌注桩试桩之前的单桩极限承载力标准值可按《建筑桩基技术规范》(JGJ 94—2008)中桩侧阻力和桩端阻力增强系数的上限值进行估算。研究结果可为苏州地区大直径超长后注浆钻孔灌注桩的类似工程设计提供参考。

Experimental study on large-diameter super-long post-grouting bored cast-in-place pile in Suzhou

The determination of reasonable grouting volume and ultimate bearing capacity of single pile for large-diameter super-long post-grouting bored cast-in-place pile has become the problem in design. The reinforcement mechanism and grouting method of post-grouting bored cast-in-place pile were introduced. The test pile data of the large-diameter super-long post-grouting bored cast-in-place piles with different pile diameters and embedded in different bearing layers in Suzhou Central Plaza Project were emphatically introduced. The bearing performance of the large-diameter super-long post-grouting bored cast-in-place pile was analyzed combined with the test data of large-diameter super-long post-grouting bored cast-in-place piles of 4 super high-rise buildings around Jinji Lake in Suzhou. According to the relevant formulas in Technical code for building pile foundation(JGJ 94-2008) and Foundation design code of Shanghai(DGJ 08-11-2010), the single pile grouting volume and single pile standard value of ultimate bearing capacity were estimated, and the estimations were compared with experimental data. This suggestion is provided that the reasonable range of grouting volume of pile end of the large-diameter super-long post-grouting bored cast-in-place pile with a diameter of 1000 mm is 2~4 t under similar geological conditions in Suzhou, and that the single pile standard value of ultimate bearing capacity of the large-diameter super-long post-grouting bored cast-in-place pile before the pile test can be estimated according to upper limit value of pile side resistance and pile end resistance enhancement coefficients in Technical code for building pile foundation(JGJ 94-2008). The research results can provide reference for similar engineering design of large-diameter super-long post-grouting bored cast-in-place pile in Suzhou.