坝后背管外包混凝土厚度研究

采用平面非线性有限元法对某水电站下游面钢衬钢筋混凝土压力管道进行了分析，计算中考虑混凝土开裂和地震作用的影响。研究了5种外包混凝土厚度0.5、0.8、1.2、1.5和2.0m的坝后背管在内水压力和地震作用下的承载规律，分析了外包混凝土厚度对管道的动、静力承载性能的影响。结果表明，设计内水压力作用下，外包混凝土厚度较小时，管坝接缝面附近的局部坝体开裂，并使管道钢材应力提高，但其材料强度和变形仍能满足规范要求。地震作用分析表明，外包混凝土越厚，坝后背管结构的基频值越高；但厚度越大，管道钢材动应力值也越大，说明采用较小的外包混凝土厚度有利于减小钢材的动应力。因此，在满足施工要求和安全的前提下，建议在坝后背管设计中采用厚度较薄的外包混凝土。

Study on wall thickness of steel lined reinforced concrete penstock laid on downstream surface of dam

The plane nonlinear FEM is applied to analyze the steel lined reinforced concrete penstock laid on downstream surface of dam in a typical hydropower station. In the analysis, the effect of cracking in concrete and earthquake are taken into account. The bearing capacities of the penstock under the actions of internal water pressure and earthquake for 5 thicknesses of concrete are calculated and the effect of concrete thickness on the static and dynamic bearing capacity of the penstock is analyzed. The results show that in case the thickness of concrete layer is comparatively small, cracking will occur to the concrete of the dam in the vicinity of combination between dam and penstock. In spite of the stress of steel penstock increases, the strength and deformation will not exceed the limit of design criterion. Besides, the more the thickness of concrete, the higher dynamic stress of the steel penstock will happen. It is suggested that a smaller thickness of concrete layer is preferable if the requirements of safety and construction of the penstock are fulfilled.