Abstract：The engineering scale of tailrace system at Xiangjiaba right-bank underground powerhouse is very huge. Restricted by the terrain and geological conditions，the design and construction face lots of difficult technological problems. According to this actual situation and by means of numerical calculation and physical model test，some advanced design plans such as tailrace tunnel with the ceiling height change and 2 adits merged to 1 tunnel，are adopted；and some special construction plans such as top arch lining first，then excavation down，and small holes in large holes，are adopted. Safety monitoring guides construction to ensure the safety of engineering. Deformation of surrounding rock gradually inclines to be stable after excavation. The maximum measured deformation at top arch is 13.25 mm，close to the theory value of 15.72 mm. The comparative result shows that the design parameters of excavation and support are reasonable；and the sequence and method of construction are successful.
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2012, Vol. 31 
