钢绞线逐根张拉下锚墩基床沉陷所致锚索预应力损失问题

在预应力锚索锚墩下部地基岩土的基床系数较低情况下,采用钢绞线逐根张拉来施加预应力会导致较大的预应力损失以及各钢绞线较显著的预应力不均。基于锚墩基床岩土体的弹性压缩模型,理论探讨了钢绞线逐根对称循环张拉下的锚索预应力损失,及钢绞线的预应力均匀性问题。分析表明,基床系数越低,逐根张拉下的锚索预应力损失越大,且其所含各钢绞线预应力的均匀性越差;而同样荷载和基床系数下,锚索所含钢绞线根数越多, 逐根张拉后的预应力损失和不均匀性也越大。但采用分级循环张拉、正序张拉及调整、锚墩下部一定扩散角填石等工序及措施有助于减轻预应力损失和解决不均匀性问题。

TENSION LOAD LOOSENING OF PRE-STRESSED ANCHOR CABLE WHEN ANCHOR BLOCK SUBGRADE COMPRESSED ACCOMPLY WITH TENSION LOADS APPLIED TO STEEL STRANDS ONE BY ONE

When the coefficient of subgrade reaction of soils under the anchor block is low, if the tension loads were applied one by one to steel strands of the cable, tension load loosening of pre-stressed anchor cable will occur. And lead to distinct different tension loads among steel strands. Based on elastic compressing model of the subgrade under anchor block, when tension loads were applied one by one to steel strands, the tension load loosening of pre-stressed anchor cable can be discussed. By means of this theoretic mechanical model, conclusions can be drawn: the lower the coefficient of subgrade reaction, the evidently the tension load loosening, and more distinct difference of tension loads among steel strands. The amount of strands in the cable more, the load loosening and the difference of loads evidently. It indicated that, applying load by stages, by a just sequence, and stuffing rocks under anchor block, conduce to abating the tension load loosening and increasing unanimous of loads to an extent.