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小浪底水利枢纽工程的３ 条排沙洞， 洞身７０％ 以上采用后张法无粘结预应力混凝土衬砌。其张拉系统的施工主要包括钢绞线的就位、固定， 锚具槽、锚具及张拉设备的安装， 张拉等步骤， 施工工艺严谨。三维有限元分析结果表明， 张拉时锚具槽附近将出现明显的应力集中， 为此， 采取了分步张拉、加箍筋等措施， 达到对预应力的控制， 也避免了产生贯穿性裂缝。为了保证锚索及锚具的防腐、抗磨性， 采用了套管和封闭构件及控制过水面不平整度等措施。小浪底工程排沙洞采用这种衬砌结构的经验可供其他工程借鉴。
Xiaolangdi Water Control Project of the three sand discharge tunnel, more than 70% of the hole body using post-tension method of unbonded prestressed concrete lining. The construction of its tensioning system mainly includes the installation of steel strands in place, fixing, anchoring groove, anchoring and tensioning equipment, and tensioning. The construction process is rigorous. The results of three-dimensional finite element analysis show that there will be obvious stress concentration near the groove of the anchor during tensioning. Therefore, some measures such as step-by-step tensioning and stirrup reinforcement are adopted to achieve the prestressing control and prevent the occurrence of penetrating crack. In order to ensure the anti-corrosion and abrasion resistance of the anchor cable and the anchorage, the casing, the closed components and the control of the unevenness of the water surface are adopted. Xiaolangdi project sediment discharge tunnel lining of this experience can be used for other projects.