By means of software ABAQUS,a spiral case structure of hydropower station was calculated with three-dimensional finite element method so as to discuss the in-plane scope of local cushion layer set in spiral case structure.When the end of the local cushion layer starting at the straight pipe inlet changed between section 45° and section 135°,the bigger the scope was,the better to improve the load status of concrete structure around the spiral case. It was fully capable to limit the width of concrete cracks and reduce the non-uniform displacement of the rise of generator pier effectively as the local cushion layer was set to end at section 45°.Besides, when the cushion layer was set to end at section 45°,the shearing force loaded on the stay ring would increase less basing on that of the complete bearing spiral case structure.This was beneficial to the whole structure. Based on these analysis and considering the simplification of the construction procedure,the local cushion layer set in spiral case structure of hydropower station ending at section 45° was worth to be selected.
