高速铁路CFG桩+挤密桩工程实践及研究

Engineering Practice and Research on the High Speed Railway Composite Foundation with CFG Pile + Compaction Pile

研究目的：高速铁路CFG桩＋挤密桩复合地基是近年新兴的针对上部为湿陷性土地层、下部为松软土地层的湿陷性黄土地基处理技术，在国内外均无成熟的实践经验，需要结合工程实践对其布桩组合形式、计算方法、施工工艺及沉降控制经验系数等进行系统地研究。研究结论：（1）CFG桩＋挤密桩长短桩复合地基沉降计算复合模量宜采取复合模量法结合承载力比值的确定方法；（2）该技术处理的湿陷性黄土地基主沉降一般在3—6个月可完成总沉降量的90％-95％；（3）沉降计算经验修正系数在模量当量值大于15MPa宜取0．3，模量当量值大于20MPa时宜取0．2—0．25；（4）湿陷性黄土地基长短桩采用正方形布置形式更便于现场施工和质量控制，宜优先采取正方形布置方案处理地基；（5）为减小缩孔缩径断桩影响，作为长桩的CFG桩宜采取较高无侧限抗压强度的桩体材料；（6）该研究成果对湿陷性黄土地区高速铁路路基的地基处理具有推广应用价值。

Research purposes： In recent years, the high speed railway composite foundation with CFG pile ＋ compaction pile is the emerging foundation treatment technology for the collapsible loess ground with upper wet - soil layer and bottom soft -soil layer. There is no mature practical experience at home and abroad. The cloth pile combination form, calculation methods, construction technology and sedimentation control empirical coefficient all need the validation from engineering practice. Research conclusions： （ 1 ） The composite modulus of the composite foundation with long - short - piles of CFG pile ＋ compaction pile are appropriate to take the composite modulus method in combination with the determination of bearing capacity ratio. （2） Under this technical treatment, 90% - 95% of the total collapsible loess foundation settlement can commonly be settled in 3 - 6 months. （3） The value of correction coefficient in settlement calculation can take O. 3 when the modulus quantity is greater than 15 MPa, the value of correction coefficient in settlement calculation can take 0.2 - 0.25 when the modulus quantity is greater than 20 MPa. （4） Using a square layout in the collapsible loess long - short- pile is easier for site construction and quality control, so a square layout should be preferred to the ground treatment scheme. （5） To reduce the effect of shrinkage, hole shrinkage and broken pile on the CFG pile of the long pile, pile materials with the higher unconfined compression strength are the first choice. （6） The research result has higher application value to promote the foundation treatment of high speed railway in collapsible loess areas.