Underlying tuff, bedrock surface buried depth is 8~9m, and bedrock surface fluctuates greatly.
2.
1 Cross-sectional view of single box with three compartments of approach bridge box girder/cm
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The lower layer is distributed with marine silt, gray, with a thickness of 6-10m.
The geological conditions and surrounding environment are complex.
The underlying granite porphyry and tuff are hard, and the bedrock surface is buried 3~6m deep.
The flange plate cantilever is 2.45m, the standard thickness of the top plate is 0.28m, the standard thickness of the bottom plate is 0.25m, and the standard thickness of the web is 0.6m.
The box girder is gradually lifted from small mileage to large mileage.
1.3 Engineering geological conditions The main pier at the north side of Xuanmen Bay Bridge is located in the water area of Xuanmen Port.
The top plate of the box girder is 16.215m wide, the bottom plate is 10.225m wide and 2.2m high, the flange plate cantilever is 2.45m, the standard thickness of the top plate is 0.28m, the standard thickness of the bottom plate is 0.25m, and the standard thickness of the web is 0.6m.
The foundation of the box girder support is partly on the land, partly in the water, partly at the junction of half water and half land.
(2) The single box and two-compartment box girder is generally constructed with the fifth section of the left approach box girder and the seventh section of the right approach box girder.
With the completion of the second phase of Xuanmen Bay reclamation, the water area at the bridge site has become a closed water storage area.
The lower layer is distributed with cohesive soil gravel, brown yellow, with a thickness of about 1~2m.
After comprehensive consideration, the box girder support scheme is selected as follows: Fig.
The geological conditions of the approach box girder bridge site selected for the box girder support scheme are complex.
The filled soil mass may have lateral slip and poor stability.
There is no water exchange with the sea water in the Yueqing Bay outside.
The main pier on the south side of Dumen Port Bridge is located in the water city of Xuanmen Port, and the newly deposited silt, grayish yellow, flowing plastic, is distributed on the surface of the water bottom, with a thickness of about 2~3m.
The water surface is stable, the water level changes little, and the water quality is gradually desalinated.
According to the design drawings, after the removal of Xuanmen Dam, the normal water level is 0.0m, and the navigable water level is 0.2m; Through continuous observation, the water level elevation during construction is about -0.6~-0.3m.
After several attempts, it cannot be filled into the whole land state.
This paper focuses on the design and construction of cast-in-place support for box girder under complex geological conditions, providing reference for similar projects.
1.2 Hydrological conditions The Xuanmen Bay Bridge is located inside the Xuanmen Dam.
There is a steep inclined rock surface in the geological transverse direction of the bridge.
The half land and half water bridge site is located at the foot of the slope near the mountain.
Affected by the horizontal curve of the bridge beam, the top plate of the box girder is 18~19.375m wide, the bottom plate is 12.975~13.475m wide, and the height is 2.2m.
The terminal part crosses the existing access road.
At the end of the box girder, the overpass of the existing access road is connected with the Xuanmen tunnel, and the overpass part needs to be set with a door hole to ensure the passage of vehicles.
The support foundation is located in the states of land, water and half land and half water.
1 Project overview 1.1 Design overview of box girder (1) General layout of box girder of approach bridge There are 4 cast-in-place box girders of approach bridge on the left side of Xuanmen Bay Bridge, of which the split of small stake side is as follows: 3 × 35m+3 × 35m=210m, the split at the side of large pile number is: 2 × 35m+2 × 30m=130m; A total of 6 cast-in-situ approach box girders are set on the right side, of which the split at the small stake side is: 4 × 35m+3 × 35m+3 × 35m+3 × 35m=455m, the split at the side of large pile number is: 2 × 35m+(35m+25m)=130m。 (2) The general structure of the approach box girder (1) The single-box three-compartment box girder is generally composed of the first to second and fourth sections of the left approach box girder, and the first to fourth and sixth sections of the right approach box girder are all of single-box three-compartment structure.
The starting point of the approach bridge is connected with the existing road, and the clearance under the bridge is insufficient.
The newly deposited silt, grayish yellow, flow plastic, is distributed on the surface of the water bottom, with a thickness of about 2~3m.
Abstract: The approach box girder of Xuanmen Bay Bridge and its connection project in Yuhuan City is located along the coast.
