小浪底水库排沙洞工程预应力混凝土衬砌方案选择

Selection of Pre Stressed Concrete Lining System for Sediment Tunnels for Xiaolangdi Multipurpose Dam Project

小浪底工程排沙洞预应力混凝土衬砌原设计为有粘结筋方案．在招投标期间，承包商提出采用无粘结筋作为替代方案．为了对两种方案进行慎重选择，在现场进行了１∶１室外模型试验．试验结果表明，无粘结筋方案具有张拉时摩擦损失小，可采用双圈布置，预压应力均匀，结构受力性能好，张拉槽数量少，施工简单、方便，节省材料等优点．

Bonded tendons for pre stressing of concrete sediment tunnel liners were proposed in the original design documents of the Xiaolangdi Project.The contractor suggested to use unbonded tendons instead of bonded ones at the time of tender.Full scale (1∶1) in situ tests were performed for the selection of the best scheme.Test results indicated that unbonded tendons developed less friction loss after stressing.Other advantages,were also shown,for example,better stress distribution.better load resistance,lower number of block outs due to double loop layout,easy and convenient use in construction,lower cost and less time consumption,etc.