深厚软土桥梁桩基荷载传递特性及沉降控制效果研究

通过杭甬铁路客运专线柯桥特大桥单桩静载试验,桩身应变、桩身压缩量及桥墩沉降的测试,研究深厚软土地区桥梁桩基的荷载传递特性及沉降控制效果。结果表明:桩侧摩阻力先于桩端阻力发挥作用;尽管桩端置于强风化凝灰质砂岩上,但在试验荷载下2根超长试验桩的端承比均小于1.5%,桩的承载特性表现为摩擦桩的性质;单桩静载试验实测的桩身压缩量占桩顶沉降量的85%以上;桥墩浇筑完成后经过753d的沉降观测,2个试验墩实测沉降量分别为3.00和3.41mm,其中,无砟轨道铺设后300d的实测沉降分别为0.11和0.25mm,表明在深厚软土地区采用超长钻孔灌注桩控制桥梁基础沉降的效果显著。

Study on the Load Transfer Characteristics and Settlement Control Effect of Bridge Pile Foundation in Deep Soft Soil

The load transfer characteristics and settlement control effect of bridge pile foundation in deep soft soil was investigated through single pile static load test,pile strain test,pile shaft compression test and bridge pier settlement test on Keqiao super large bridge of Hangzhou-Ningbo passenger dedicated line.The results show that the frictional resistance of pile side plays its role prior to pile end resistance.Although the ends of two super-long tested piles are embedded in the strongly weathered tuffaceous sandstone,their end-bearing ratios under various test loads are less than 1.5%.The bearing properties of the piles present as that of friction pile.The compressions of pile shaft accounts for more than 85% of the settlement at pile top during single pile static load test.After 753 days’ settlement observation on the two tested piers since their completion,the measured settlements of two tested piers are only 3.00 and 3.41 mm respectively.Among them the measured settlements 300 days after the laying of ballastless track are 0.11 and 0.25 mm respectively,which illustrates that super long bored piles can effectively control the settlement of bridge foundation in deep soft soil.