Study on the Reasonable Width of Vehicle Cross Passageways of the Jiaozhou Bay Second Subsea Tunnel

The cross passage for separated double-hole road tunnels plays an important role in emergency rescue. At present, the design research on the width of the cross passage in large-scale subsea tunnel projects in China is still blank. Using the research methods of data investigation, theoretical analysis, and comparative demonstration, the reasonable width of the vehicle cross passages in the design process of the Jiaozhou Bay Second Subsea Tunnel was studied. The research content includes research on the main driving parameters of fire trucks in the subsea tunnel, investigation and analysis of the minimum turning radius of rescue vehicles inside the tunnel, comparison and demonstration of the clear width required for rescue vehicles to enter and exit the main line tunnel from the cross passage, comparative analysis of the width required for rescue vehicles to enter and exit the service tunnel from the cross passage and research on the project cost of different width cross passages, etc. The result shows that (1) when a vehicle turns at right angles, the 3 lane widths of the main line tunnel are (3.75+3.5+3.5) m, which meets the requirement of the minimum width before turning; (2) when the width of the vehicle cross passage is 4.0 m, it needs to be widened locally if fire trucks turn into the cross passage at the edge of the cross passage from the left, middle, and right of the main line; (3) when the width of the vehicle cross passage is 6.0 m, the fire trucks can transfer from the main line tunnel to the vehicle cross passage at one time, and from the vehicle cross passage to any lane of the main line tunnel at one time, which can provide favorable conditions for tunnel rescue; and (4) when the pavement width of the cross passage increases to 8.0 m, it can turn in or out between the cross passage and any lane of the main line tunnel, and it only adds the function of turning into the vehicle cross passage from the left lane at one time compared with the 6.0 m wide pavement. Comprehensively considering the use function, the difficulty of project construction, and the economy, it is recommended that the pavement width of the vehicle cross passage be 6.0 m. The research result can be applied to project design to provide reference for subsequent subsea tunnel project design and construction.