2.4.2 Breaking and Temporary Sealing of the Tunnel...
1）Broken of tunnel door
When the shield reaches the back of the continuous wall，the concrete of the continuous wall in the tunnel door is broken by artificial air pick.The continuous wall chiseling of the tunnel door is carried out twice：For the first time，the palm surface of the hole door is divided into 9 pieces，and the reinforcement outside the continuous wall is cut off from top to bottom，and then the concrete of the main body of the continuous wall is chiseled out to retain the steel bar in the inner layer of the continuous wall.After the second time，the innermost steel bar is quickly removed after the shield opening chamber is checked for no leakage and the joint acceptance is completed.When the steel bar is removed for the second time，it is necessary to check the clearance of the shield to ensure that no steel bar invades the penetration range of the shield.
The continuous wall of the entrance of Nanjing Yangtze River Tunnel is chiseled three times：The outer concrete 10 cm is broken for the first time，and the steel bar in the inner layer of the underground continuous wall is removed.The second break is arranged after the freezing is completed，the concrete is broken 50 cm，and the temperature holes（a total of 35）are drilled on the door to detect whether the freezing has been completed.The third break is carried out in two stages.In the first stage，the thickness of concrete is 30 cm after the detection hole temperature（≤-2℃）meets the design requirements.In the second stage，the remaining 10 cm concrete and the outer steel bar of the underground continuous wall are broken within 2 days，and the exposure time of the frozen palm surface does not exceed 2 days.
2）Temporary sealing of tunnel door
After the shield tunneling，the small machine is used to clean up the mud during the penetration in time，and then the temporary sealing device of the tunnel door is installed.The temporary sealing device of the end tunnel door is similar to that of the beginning，the fixed bolt hole shall be welded outside the flip plate，and the temporary sealing device of the tunnel door shall be tightly affixed to the outer arc surface of the segment by tightening the wire rope pierced through the bolt hole.
After the receiving base is installed and fixed，the shield can push the receiving base slowly.When passing through the temporary sealing device of the tunnel door，butter is applied to the outer ring of the knife plate and the tool to prevent the shield cutter head and the tool from damaging the curtain rubber plate.When the shield is pushed on the receiving pedestal，the temporary sealing device of the tunnel door is tightened every time the shield is pushed forward 2 rings forward，and the outer annular gap of the pipe piece is filled with quick setting slurry through the synchronous grouting system，so as to ensure the correct attitude of the segment.
After the assembly of the last ring segment，the temporary sealing device of the tunnel door is tightened，so that the curtain rubber plate and the outer arc surface of the segment are tightly affixed，and the tunnel door ring is filled with grouting through the segment grouting hole.In the process of grouting，we should pay close attention to the situation of the cave door.As soon as the phenomenon of slurry leakage is found，the grouting should be stopped and the sealing treatment should be carried out to ensure that the grouting at the entrance is dense and the ring sealing of the hole door is tight.