| Most of the underground drainage and observation galleries below the bottom of the upper reservoir of Tianhuangping Pumped-storage Power Station (PPS) consist of the precast concrete arch and the on-site cast concrete side wall and floor. During the operation of the power station, cracks which were about O.lmm to 0.15 mm wide occurred along the axial direction of the 7th gallery's floor. The cracks were periling the normal operation of the power station, and the strengthening of the gallery was badly needed.In order to recognize the reasons for cracking and present an effective strengthening scheme, finite element method (FEM) analysis based on the platform of ABAQUS was performed before strengthening. Before and after the strengthening, nonlinear FEM analysis and on-site experiments were implemented, which verified the rationality of the strengthening scheme and the effect of the strengthening.The major content of this thesis are as follows:1) Performed FEM analysis before strengthening, and to find out the reason for the cracking and present a strengthening scheme;2) Performed nonlinear FEM analysis before and after strengthening, and to get the varying rule of the relative displacement between the on-site cast concrete side wall and that between the precast concrete arch and the floor, as well as the stress distribution of the gallery;3) Performed on-site observation experiments on the 7~th gallery, and to get the varying rule of the relative displacement between the on-site cast concrete side wall, as well as that between the precast concrete arch and the floor.4) The results of the computation were compared with those of experiments, which verified the effect of the strengthening.Results showed:1) The dominative reason for the floor's cracking is the over breaking of the gallery;2) The strengthening scheme is reasonable and the effect of strengthening is distinct.
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