Abstract
The mechanical behavior of lining structure of deep-embedded cylinder surge shaft with multifork tunnel is analyzed using three-dimensional nonlinear FEM. With the elastic-plastic constitutive relations of rock mass imported and the implicit bolt element and distributed concrete cracking model adopted, a computing method of complex surge shaft is presented for the simulation of underground excavations and concrete lining cracks. In order to reflect the interaction and initial gap between rock mass and concrete lining, a three-dimensional nonlinear interface element is adopted, which can take into account both the normal and tangential characteristics. By an actual engineering computation, the distortion characteristics and stress distribution rules of the dimensional multifork surge-shaft lining structure under different behavior are revealed. The results verify the rationality and feasibility of this computation model and method and provide a new idea and reference for the complex surge-shaft design and construction.
Highlights
The surge shaft of hydropower station is a typical building in underground engineering
The concrete lining structure is built after excavation and support of surge-shaft chamber, considering the influence of chamber deformation on lining structure; the plastic load {Rp} released from surge-shaft excavation could be divided into two parts:
Comparison is made with the calculated results of considering concrete lining as linear elastic material and nonlinear material with cracking, which indicates that the latter is more efficient to reflect the real stress condition of lining, and the calculating method of concrete lining structure with cracking is shown to have practical significance
Summary
The surge shaft of hydropower station is a typical building in underground engineering. The two most popular methods at present are traditional structural mechanics method and FEM As to the former, the effect of surrounding rocks on lining was reflected by considering the pressure and elastic resistance of rocks, without considering the deformation compatibility and internal force adjustment in the lining-rock interaction, and the results cannot properly reflect the real stress state of structure. Papers [5,6,7,8,9,10] use FEM to analyze the stability of surrounding rocks and operating characteristics of lining in simple formal underground structure but did not involve the analysis of complex multifork surge-shaft structure. By an actual engineering computation, the structural stability, the distortion, cracking characteristics, and the stress distribution of complex multifork surge shaft lining under different condition are revealed, which verifies the rationality and feasibility of this computing method and provides some helpful ideas and references for the structure design and construction
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