不同持力层钻孔桩桩底后注浆应用效果分析

本文首先简单介绍了钻孔桩桩底后注浆的机理和工艺技术。采用分层位移迭代法对不同桩基持力层注浆前后的Q-s曲线进行了理论分析,发现持力层从粘土→粉砂→砾石层,颗粒越粗,桩底后注浆的效果越好。还通过试桩作了注浆前后的对比静力试验,得出了以下结果:桩的承载力的增幅注浆后比注浆前一般可提高20%30%,对砾石持力层,可超过40%,且沉降量明显减少;注浆后桩身轴力可发挥更大潜力;注浆后桩侧摩擦力能明显提高。文末,并对砾石层、粉砂层、粘土层及基岩四种持力层的钻孔桩桩底后注浆的适用性和应用效果给出了分析结论。

The Application Effect Analysis of Post grouting Under Bored Piles with Different Bearing Strata

The mechanism and technology of post grouting in bearing stratum under bored pile tip are briefly introduced at first in this paper. The layerwise displacement iteration method is used to analyze theoretically the Q s curves of post grouting bored pile with different strata, it is found that the bearing strata from clay to silty sand to gravel are, the more coarse the grain of bearing stratum, the better the effect of post grouting. Through the comparable static loading test of piles before and after post grouting under pile tip, the following results are obtained: the bearing capacity of pile after grouting can be increased by 20%～30% for silty sand stratum, and more than 40% in the case of gravel stratum, while the settlement is obviously decreased; the potential of axial force of pile shaft can be fully utilized after grouting; the side frictional resistance after grouting is distinctly increased as well. Finally, some conclusions about the applicability and application effect of post grouting under bored piles with four kinds of bearing strata, i.e. gravel, silty sand, clay and bedrock strata, are drawn.