Effect of Temporary Internal Water Pressure on Structural Performance of Spiral Case Structure in Pumped-Storage Power Plants

Abstract

Temporary internal water pressure (IWP) during a construction period fundamentally affects the structural performance of spiral case structures (SCSs) in pumped-storage power plants (PSPPs). However, its actual role is rarely studied. This study focuses on this issue considering the complex construction-to-operation process of SCSs. An ABAQUS-based complete simulation procedure (CSP) is used with contact non-linearity considered. The contact-closing ratio is introduced to quantitively describe the contact status, and different design philosophies for temporary IWP are compared. The results show that the temporary IWP should be no greater than 80% of the minimum static headwater to ensure an overall contact-closing status under normal operating conditions in this study. The findings reveal that the cracking risk of concrete is negatively correlated with temporary IWP, while high temporary IWP is not suggested. Moreover, the stay ring actually shares a certain part of the unbalanced hydraulic thrust, which cannot be ignored. The limitation of this study might mainly lie in the idealized linear-elastic description of concrete. The temporary IWP should be designed with overall consideration of the IWP under normal operating conditions, the IWP-jointly-resisting status and design demands.

Embedment of Steel Spiral Cases in Concrete: Lessons from a Structural Deformation Accident in China

“…The classical coulomb friction model is adopted to simulate the interaction between the SSC and concrete structures. The friction coefficient is defined as 0.25 with overall consideration of the authors' previous work [17], as well as the research of Rabbat and Russell [19], Baltay and Gjelsvik [20], Zhang [21], Hu [22] and Zhang [23].…”

“…Besides, for an average P-type SCS, the mass of the water inside it during pressurization can reach 1 × 10 6 kg, which might help a lot resisting the raising displacement of the SSC during the construction of concrete. However, the current study concerning temporary IWP mainly focuses on its effect on the contact between the SSC and the concrete [14][15][16][17], and the effect of the gravity of water inside has been long neglected. During the construction period of a 700 MW class turbine set with M-type SCS in China, a structural deformation accident happened with the maximum raising deformation of 45 mm of the SSC, and it took over four months to remove about 1200 m 3 concrete before reconstruction, causing severe economic loss [18].…”