褥垫层厚度对复合地基CFG桩土应力比影响的试验研究

褥垫层厚度设置是否合理,对水泥粉煤灰碎石桩（CFG桩）复合地基的承载与变形特性将产生较大的影响。在江西某高速公路采用CFG桩加固软土地基试验现场,对不同褥垫层厚度工况下的桩土应力比进行了现场静载试验测试,并模拟各个工况对桩土应比和土体沉降进行了定量数值计算,研究结果表明：数值计算结果与实测值较为接近,具有相似的变化规律,在桩长和桩间距一定的条件下,桩土应力比随垫层厚度的增加而减小,但褥垫层超过一定水平,厚度对桩土应力比的影响较小。在路堤荷载作用下,当桩间距为1.5 m,褥垫层采用中粗砂时,厚度宜为30～40 cm。该研究成果可为该地区高速公路CFG桩加固软土地基的设计提供参考。

Experimental Study on Effect of Cushion Thickness to Pile Soil Stress Ratio of CFG Composite Foundation

The design of cushion thickness will produce bigger effect on the bearing and deformation of cement fly ash gravel pile（CFG pile） composite foundation.Pile-soil stress ratio of CFG pile composite foundation was measured under the condition of field static load test with variable cushion thickness in one expressway in Jiangxi province,and quantitative numerical calculation for the pile soil ratio and settlement of CFG pile composite foundation was carried out.The results show that： the numerical calculation results and the measured value are relatively close,with similar changes in the law.Under the certain pile length and pile spacing,the stress ratio of pile-soil decreased with the increase of cushion thickness.But when the thickness of cushion is above a certain value,it influenced less on the stress ratio of pile-soil.Under the load of embankment,the thickness of cushion,which was made up of coarse sand,should be 30 cm to 40 cm while the pile spacing was 1.5 m.The research results could provide reference for the design of CFG pile composite foundation in the freeway of this area.The research results in this paper could be used as a reference for the design parameters of CFG-pile composite foundations for freeway soft foundation in this region.