RESEARCH ON THE DESIGNS OPTIMIZATION OF MAIN FOUNDATION PIT BRACING PROJECT OF LUCHENG STATION IN CHANGZHOU METRO TUNNEL

The depth of excavation in standard section is about 16.49m, and the pit depth of the east and west ends of the well location is about 17.72m and 18.21m respectively, the main soil layer on the foundation pit is cohesive soil and silty clay in Lucheng Railway Station of Changzhou Metro 2. Bored pile with bracing retaining and protection plan was employed in subway station deep foundation excavation project through the optimization design and demonstration, for realizing the design ideas of feasible technology, economical, practical and safe, environment-friendly and fuel-efficient. Three-axis mixing pile(high pressure jet grouting pile is used under the high voltage line) waterproof wall is adopted outside the foundation, and the tube well precipitation(drainage well, decompression well) is utilized inside the foundation. Compared with the diaphragm wall(internal support),the retaining structure of bored pile can reduce the cost of construction by about 30%under the same support condition. The engineering practice proves that the design scheme of the support project has reached the expected goal.