高拱坝坝踵应力实测与弹性计算结果差异原因分析

坝踵应力是关系到混凝土坝是否开裂和安全的一个重要指标，不管是用结构力学法还是有限元法都能计算出坝踵有一定的拉应力，但实际监测中却很少出现。本文从定性和定量两个方面分析造成计算结果和实测结果差异的原因，以小湾特高拱坝为例分析影响计算精度的各项主要因素，在此基础上提出坝踵真实应力的仿真分析方法。结果显示，计算和实测应力差异原因主要在于以下三个方面：1）坝踵位置的定义不同；2）目前监测仪器和方法有局限性；3）计算过程中的不当简化，如自重和水压的施加方式、坝体温度荷载的考虑、库水温度分布以及库盆水压的影响等。改进后的仿真分析结果与监测结果吻合良好，说明该方法能够给出合理的坝踵应力变化规律和比较精确的应力范围。最后，给出了坝踵应力监测仪器和方法的改进建议。

Analysis of Difference Reason Between Monitoring and Elastic Calculating Dam Heel Stress of High Arch Dams

The dam heel stress is a key indicator that is closely related to concrete cracks and dam safety. Tension stress is generally got in a dam heel by structure mechanics methods or finite element methods, while seldom be monitored with instruments. The reason for the difference between simulation and monitoring results is analyzed qualitatively and quantitatively. Main factors affecting simulation accuracy are studied with Xiaowan arch dam as an example, and an improved simulation method is proposed to give more real and accurate dam heel stress. The results show that the reason mainly lie in the following three aspects: different dam heel definition between simulation and monitor, limitation of monitoring methods and instruments, improper simplification in simulation analysis, such as self weight and water pressure consideration, temperature load of a dam, reservoir water temperature distribution and impact of basin water pressure etc. The simulation results got with the improved simulation method are in good agreement with the monitoring results of Xiaowan arch dam. Therefore, reasonable stress variation and accurate stress range can be obtained with the improved simulation method. Finally, some suggestions for improvement of monitoring instruments and methods are given.