砂土中静压桩挤土时效性的室内应变保持试验研究

LABORATORY STRAIN-HOLDING TESTS OF SET-UP OF JACKED-IN PILES IN SAND

工程实践中发现砂土中的挤土桩承载力亦有时效性,超静孔隙水压力消散理论无法解释该现象。利用应力路径三轴仪进行应变保持试验,模拟沉桩及随后的桩周土体的应力状态和物理性质的改变,经分析试验结果得出,砂土中静压桩承载力时效性是由于桩周土体蠕变膨胀引起桩壁上作用的水平应力增大的结果。

It is well-established that the shaft capacity of piles jacked-in increases with time. In clays, this behaviour arises predominantly from the dissipation of positive excess pore pressures. In sands, this increase in the absence of pore pressure dissipation can＇t be attributed to the aforementioned mechanisms. A series of triaxial strain-holding tests are conducted, and a hypothesis is proposed to explain pile set-up in sand that an increase in radial stress due to restrained creep dilation of the soil close to the pile shaft causes an increase in Shaft resistance.