Project name: Dalian Metro Line 5 Lot 04
Constructor: China Railway First Engineering Group Co., Ltd.
Shield model and diameter: China Railway Equipment 12.26m slurry shield
Product used: CONDAT WR90NG; CONADT WR89NG； CONADAT HBW NG

Project overview:

The section between the railway station and the South Barracuda Bay Station is 3316.414 meters long, the large shield section is 2870 meters long, and the small shield section is 446 meters long, of which the large shield section is 2310 meters long, the sea crossing section is 9-14 meters deep, and the seabed is 12.2-22.8 meters away from the top of the tunnel. The single hole double layered lining scheme is adopted. The inner diameter of the segment is 10.8 meters, the outer diameter of the segment is 11.8 meters, the ring width is 2.0 meters, and the segment thickness is 50 centimeters

The geological conditions in the section are complex. The tunnel mainly passes through strongly moderately weathered slate, strongly moderately weathered dolomitic limestone, moderately weathered diabase and other strata. The high risk is mainly reflected in the high hole penetration rate, large scale, and various filling forms
The subsea construction section is faced with long distance full face hard rock excavation, with the highest rock compressive strength of 118 MPa; The deepest distance from the tunnel bottom to the sea level is up to 49m. The crossing stratum is broken, with strong water permeability, and it is connected with seawater. The water head pressure is large, close to 0.5MPa; The shield tunneling will pass through 1538m karst stratum with strong karst development. It will pass through three groups of karst caves (thousands of karst caves), with the maximum karst cave height of 29.8m; The shield tunneling underpasses important facilities such as railway, wharf and waterway. Shield tunneling is very difficult, and the safety risk is very high.

Difficulties:

The shield with large diameter can cross the karst cave group with high water pressure and the hard rock area on the sea floor for a long distance, which is very difficult
The construction control of the section where the shield passes through the karst cave concentrated area, fault structure, special clay and other unfavorable geology
Construction control of shield tunneling under and side crossing railways, bridges, river structures, etc
Control of waterproofing and anti-corrosion of underground structures.