基于旁压试验的桩基承载力计算分析

Calculation and analysis of bearing capacity of pile foundation based on PMT

非洲某工程桥梁基础穿越深厚砂性土,为了研究砂性地层钻孔桩承载特性,选取了主桥的TP-1和TP-2两根2.0 m直径的桩基进行现场试验及对临近钻孔进行旁压试验。试验结果表明,深厚砂性土会对成桩质量产生影响,砂性土越厚,桩端沉渣越显著。桩端沉渣会显著影响桩基沉降,使桩端阻力产生弱化和强化特性。此外,基于欧洲规范(BS EN 1997—2)旁压试验预测桩基承载力,会高估95%~140%桩基承载力,而公路桥涵规范计算的承载力也明显大于实测值。通过对旁压试验进行三段线性分类,可得到一种直接利用旁压试验预测桩基承载力的方法,相较于欧洲规范和公路桥涵规范更适用于深厚砂性土桩基承载力预测。

The foundation of a bridge in Africa passes through thick sandy soils.In order to study the bearing characteristics of bored piles in thick sandy soils,two 2.0 m-diameter pile foundations(TP-1 and TP-2)of the main bridge are chosen to conduct field tests,and pressuremeter tests(PMT)on adjacent boreholes are performed.The test results show that the thick sandy soils have an important influences on pile quality,and the thicker sandy soils will induce serious pile base sediment.The pile base sediment will significantly affect the settlement of the pile foundation,resulting in weakening and strengthening of the pile base resistance.In addition,the prediction of the bearing capacity of piles based on the PMT of European Code(BS EN 1997—2)will overestimate about 95%~140%of the bearing capacity of the pile foundation,and the bearing capacity calculated by the China’s specification for design of foundation of highway bridges and culverts is significantly larger than the measured value.A new method by performing three-stage linear classification of the PMT can directly predict the bearing capacity of piles.The proposed method is more suitable for the prediction of the bearing capacity of piles in thick sandy soil areas than the European Code and the China’s specifications for design of foundation of highway bridges and culverts.