水电站蜗壳垫层结构研究

应用三维非线性有限元研究了水电站蜗壳垫层的弹性模量、厚度和铺设范围对承载比的影响。为减轻钢蜗壳在上蝶边处的应力集中，提出在蝶形边附近一定范围内不设垫层。如果垫层铺到180°，则恰好该处外包混凝土较薄，易产生混凝土贯穿裂缝，若将垫层下延20°～30°，则该处外包混凝土变厚，可改善垫层末端混凝土受力状态。建议将垫层的厚度与弹模之比作为垫层设计的一个参考指标，并给出厚度与弹模的优化比值，可适用于一定PD值范围的蜗壳，供工程设计参考。

Study on structure of cushion layer for spiral case in hydropower station

The effects of elastic modulus,thickness and placement extent of cushion layer on bearing capacity of spiral case are analyzed using 3 D non linear FEM.It is found that the concentration of stress can be mitigated if the cushion layer at the vicinity of upper fix ring is canceled.Furthermore,if the cushion is extended to the position of 20°-30°,the stress of the surrounding concrete will be greatly improved and the crack depth will be reduced.It is suggested that the ratio of thickness to elastic modulus can be used as an important parameter in the design of cushion layer and the optimal value is recom-mended.