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水电站蜗壳采用垫层埋设技术时,软垫层会削弱混凝土对钢蜗壳的包裹和嵌固作用,影响两者间的接触状态,甚至引起脱空现象。本文首先从结构静力分析的角度定性解释钢衬-混凝土间出现脱空状态的潜在原因;而后借助非线性有限元数值模拟技术,研究可能影响两者间接触状态的结构性因素。结果表明,钢衬-混凝土间较小的摩擦系数、子午断面内垫层较大的铺设包角和垫层较小的压缩刚度是削弱混凝土包裹和嵌固作用的3个主要结构参数,但前两者在常规工程取值范围内的变化不会对钢衬-混凝土间的接触状态产生质的影响;相对而言,垫层压缩刚度对其的影响更为敏感。从保证钢衬-混凝土组合结构的整体性看,设计中适当折减垫层刚度是一种折衷但有益的技术手段。
When the volute of hydropower station adopts the technique of cushion laying, the cushion layer will weaken the wrapping and embedding action of concrete on the steel volute, affecting the contact status between the two and even causing the phenomenon of void. In this paper, we first qualitatively explain the underlying causes of cavities between steel lining and concrete from the perspective of structural static analysis. Then, by means of nonlinear finite element numerical simulation, we study the structural factors that may affect the contact state between the two. The results show that the smaller friction coefficient between steel liner and concrete, the larger laying angle of inner mezzanine cushion and the smaller compressive stiffness of cushion are the three main structural parameters that weaken the effect of concrete encasing and embedding. However, The change of the two within the scope of the conventional engineering will not have a qualitative effect on the contact state between the steel lining and the concrete; in contrast, the compressive rigidity of the cushion is more sensitive to it. From the perspective of ensuring the integrity of the steel liner-concrete composite structure, it is a compromise but useful technical means to properly reduce the stiffness of the cushion in the design.