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天津市某主塔楼桩基选用后压浆超长钻孔灌注桩,为了掌握超长后压浆钻孔灌注桩在该地层的工程特性,共设计了2组(共8根)试桩进行单桩竖向抗压静载试验。试桩中安装了振弦式钢筋计和分层沉降管以反映桩侧摩阻力和桩身分层沉降状态。对试验数据进行对比分析和计算结果表明,桩侧注浆可以明显提高超长桩的侧摩阻力;采用预压加载可以增强超长桩的弹性,减少桩顶的沉降;卸荷稳定后试桩具有桩侧阻力,桩身上段所受阻力为负摩阻力,下段为正摩阻力,同时具有的桩身轴力使试桩产生一定的压缩,其压缩量为残余变形量的重要组成部分。
In order to grasp the engineering characteristics of the extra-long post-grouting cast-in-place bored pile in this stratum, a total of two groups of 8 test piles were designed for single Pile vertical compression static load test. The vibrating wire reinforcement meter and the stratification settlement pipe are installed in the test pile to reflect the frictional resistance of the pile and the stratified settlement of the pile body. The comparative analysis of the test data and the calculation results show that the pile side grouting can obviously increase the lateral friction of the super-long pile; the pre-compression loading can enhance the elasticity of the super-long pile and reduce the settlement of the pile top; With the side resistance of the pile, the resistance of the upper section of the pile body is negative frictional resistance, the lower section of the pile is the positive frictional resistance, and the axial force of the pile body causes a certain compression of the test pile. The compression amount is an important component of the residual deformation.