不同注浆压力下复合式后注浆桩承载性能室内模型试验研究
Indoor Model Experimental Study on the Bearing Performance of Composite Post-Grouted Piles under Different Grouting Pressures

为探究注浆压力对复合式后注浆钻孔灌注桩承载力的影响，本文采用室内模型试验的方法和自行设计的压力注浆系统探究了在兰州黄土地基中，不同注浆压力下4根室内模型桩的承载特性和端、侧阻发挥性状。室内试验研究表明：复合式后注浆对灌注桩的承载力有着显著的提高，提高幅度在255%~436%之间；注浆压力通过增加浆液的上返高度来提高侧摩阻力，注浆压力越大，上返高度越高；复合式后注浆钻孔灌注桩的桩端阻力和桩侧摩阻力的发挥是不同步的，较小的桩–土相对位移下，注浆压力越大，侧阻发挥越迅速；但是端阻的发挥与注浆压力的大小无明显关系；当注浆量一定时，注浆压力过大，复合式后注浆桩的承载力提高幅度减小。
In this paper, to investigate the influence of grouting pressure on the bearing capacity of post-grouted bored piles with composite grouting technique, indoor model experiments were conducted using a specially designed pressure grouting system. The bearing characteristics and the development of end and side resistance of four indoor model piles in Lanzhou loess foundation under different grouting pressures were explored. The experimental results demonstrate that the composite post-grouting technique significantly enhances the bearing capacity of bored piles, with an improvement range of 255%~436%. The grouting pressure increases the side friction by increasing the upward migration height of the grout; the higher the grouting pressure, the greater the upward migration height. The development of end resistance and side friction resistance in post-grouted bored piles with composite grouting is asynchronous. At smaller pile-soil relative displacements, the higher the grouting pressure, the more rapid the development of side resistance. However, the development of end resistance has no obvious relationship with the magnitude of grouting pressure. When the grouting volume is constant, excessive grouting pressure reduces the improvement in the bearing capacity of composite post-grouted piles.