基坑预应力锚索初始张拉锁定值取值规律探讨

Discussion on selection law of initial stretch locking value of prestressed anchor cables in foundation pits

针对基坑工程中预应力锚索的特点,采用理论推导、算例计算、数值模拟及实例分析的方法,对拉力型、压力型、荷载分散型锚索及锚拉桩上多排预应力锚索的锁定值取值规律进行了探讨。结果表明:由于锚头刚度的差异,拉力型锚索的锁定值宜取规范规定范围的小值,而压力型锚索宜取相应的大值;荷载分散型锚索应分组张拉锁定,各分组钢绞线的锁定值与锚索自由段长度、分散间距及锚头位移有关,且离孔口距离越远,分段承载体锚索锁定值越大;锚拉桩上的多排预应力锚索应考虑锚索的张拉顺序采取不同的锁定值,基于各排锚索张拉锁定后产生的真实锚头位移的差异,上排锚索宜取较小的锁定值,下排锚索宜取较大的锁定值。相关规律可为基坑锚索的张拉锁定施工提供有益的参考。

According to the characteristics of prestressed anchor cables in foundation pit, the principles of selecting the locking values of the tensile anchor cable, pressure anchor cable, scattered-load anchor cable and multi-row anchor cable were discussed through the methods of theoretical derivation, analytical calculation, numerical simulation and example validation. Due to the difference in the stiffness of the anchor head, the results show that according to the specification range, the small locking value is adopted for the tensile anchor cable, but the pressure anchor cable requires the large locking value. Scattered-load anchor cables should be tensioned and locked by groups, and the locking value of steel strand in each group is related to the length of the free segment, dispersion distance and displacement of anchor head. The locking value of the segment bearing body increases with the enlargement of the distance away from the orifice. Different locking values are applied for multi-row anchor cables considering the cable tension locking sequence. Based on the difference of the real anchor head displacement after each row anchor cable is locked, the smaller locking value should be adopted for the upper anchor cables, but the larger locking value is for the lower anchor cables. Therefore, the obtained relevant laws can provide useful references for the stretch locking construction of anchor cables in foundation pit.