中文摘要：

保压蜗壳的计算方法在很大程度上影响了结果的精度和对结构受力特性的判断。为深入了解结构的受力特性。本文从施工流程出发，考虑保压缝隙的非均匀性和接触关系，实现了保压蜗壳的施工过程全仿真，并通过算例和理论分析，验证了算法（SUA）对保压缝隙模拟的有效性和准确性。该算法应用于糯扎渡水电站保压蜗壳的施工过程模拟，研究了非均匀保压缝隙的形成机理和接触界面的接触性态，并对外围混凝土应力做了细致分析。结果表明，初始保压缝隙具有非均匀和局部非张开特性，其主要导致原因是结构的非对称性，因此钢蜗壳与外围混凝土之间正好即无缝隙也不传力的理想状态不可能存在。座环上环板、机墩根部和蜗壳进口端腰部混凝土拉应力较大，是裂缝萌生的危险区域。此外，应力对比分析表明，简化算法和仿真算法应力分布规律基本一致，简化算法应力偏小，对结构配筋不利，仿真算法更加符合实际情况。两种算法混凝土环向应力在蜗壳腰部和底部吻合度较高，蜗壳顶部误差次之（个别地方误差达80％），而在座环上、下环板附近相差甚远。

英文摘要：

An improved simulation method base on non-uniform gap and contact is proposed for simulate the construction process of preloaded filling spiral case, called the simulation algorithm（SUA）. The method- ology proposed is effectively to capture the initial gap. It overcomes the limitation of traditional simplifica- tion algorithm which is neglecting gap and contact relationship of spiral case and concrete. By means of the method, the gap value, contact status and stress field of surrounding concrete for Nuozhadu hydropower project is mainly analyzed. The results show that the initial gap is non-uniform and local closed because of the asymmetry of spiral case structure. So, the ideal situation of no gap, no energy transfer between spiral case and surrounding concrete is not existed. The top of stay ring, the roots of turbine pier and the en- trance of spiral case is the dangerous position of crack initiation and propagation. The results indicate that compared with the simplification algorithm（SPA）, the law of stress distribution basically consistent, but the SPA method leans to be insecure, the relative error is big on top of spiral case and stay ring.