带扩大桩靴桩侧同步灌浆桩成桩过程试验研究

Experimental study on pile driving process of grouted enlarged toe pile

针对新型带扩大桩靴桩侧同步灌浆预制桩基础的施工成桩过程,开展透明土模型的试验研究.相较于传统预制桩,新桩型成桩完成后,端部扩大桩靴结构及桩周固化后的水泥浆液可以明显提升基桩端阻力和侧摩阻力,使得该新桩型具有较高的抗拔能力.通过透明土材料Laponite RD模拟软黏土施工环境,分别针对常规预制桩、带扩大桩靴预制桩及带扩大桩靴桩侧同步灌浆预制桩开展对比模型试验,采用粒子图像测速(PIV)技术进行成桩施工过程的可视化后处理,以探明该新桩型的成桩过程机理,为新桩型的进一步推广应用提供理论支撑.研究结果表明,新桩型施工挤土位移场的分布形式不同于常规预制桩,呈涡旋状,挤土位移的影响范围小于桩靴同直径的预制桩. X、Y方向的位移云图显示,扩大桩靴结构和同步灌浆施工技术使得桩周土体表面及内部施工扰动的影响范围更小,这对于挤土型桩基施工而言是十分有益的.

The transparent soil model test was conducted for the construction process of a new grouted enlarged-toe(GET)precast pile.The end resistance and side friction resistance can be significantly improved because of the expansion of the enlarged toe structure at the end and the solidification of the cement slurry around the pile,which makes the new pile type have higher uplift resistance compared with traditional prefabricated piles.Then the transparent soil material Laponite RD was used to simulate the construction environment of soft clay,and comparative model tests were conducted on conventional precast piles,precast piles with enlarged toe,and grouted enlarged-toe(GET)precast pile.Particle image velocimetry(PIV)technology was used to visualize the post processing of the pile construction process in order to explore the mechanism of the pile formation process of the new pile and provide theoretical support for the further promotion and application.Results showed that the distribution of soil displacement field in the construction of new pile types was different from that of conventional prefabricated piles,showing a vortex shape.The influence range was reduced by the enlarged toe structure and synchronous grouting technology of surface and internal construction disturbances on the soil surrounding pile,which is very beneficial for the construction of squeezed soil pile foundations.