超深黏土层超高压旋喷桩工艺试验

Test of Ultra-high Pressure Rotary Pile Process in Extra-deep Clay Layer

以张靖皋长江大桥为依托,分两阶段试验对SJT、RJP工艺在70 m深黏土层施工桩体的成桩质量、抗压强度、基底摩擦系数、抗渗性能以及地基承载力方面进行研究。结果表明:超高压旋喷地基加固工艺在桩体强度、基底摩擦、抗渗及承载力方面均满足施工设计要求,具备实施可行性;通过现场取芯分析,在桩体咬合处SJT的成桩效果优于RJP,结合SJT工艺在质量控制以及提高工效方面的优势,故选取SJT工艺开展深层地基加固;通过对比成桩质量及施工成本,可选用水泥掺量40%~45%、喷浆流量280 L/min、喷射压力48 MPa、喷嘴直径5 mm、提升速度7 cm/min作为实际施工时的施工参数。

Relying on the Zhang-Jing-gao Yangtze River Bridge,a two-stage experiment is conducted to study the construction technology of SJT and RJP in 70 m deep clay layer,pile forming quality,compressive strength,friction coefficient of base,anti-seepage performance and bearing capacity of foundation.The results show that:the ultra-high-pressure rotary jetting foundation strengthening process can meet the requirements of design and construction in terms of pile strength,substrate friction factor,impermeability and bearing capacity,thus is feasible.The results of field core analysis show that the pile formation effect of SJT process is better than that of RJP process at the pile occlusion.Combined with the advantages of SJT process in quality control and improvement of work efficiency,the SJT process is selected to carry out deep foundation strengthening.By comparing the pile quality and construction cost,the construction parameters of the 40%~45%cement mixture,280 L/min slurry flow rate,48 MPa injection pressure,5 mm nozzle diameter and 7 cm/min lifting speed could be chosen during actual construction.