Construction method of tunnel portal water stopping structure for shield excavation and shield arrival

The invention discloses a construction method of a tunnel portal water stopping structure for shield excavation and shield arrival. The construction method includes the steps that firstly, water stopping steel brushes are installed, specifically, before shield tunneling construction, two circles of water stopping steel brushes are installed in the excavation tunnel portal and arrival tunnel portalcorrespondingly, each circle of water stopping steel brushes includes a plurality of water stopping steel brushes arranged on the inner walls of portal steel rings in the circumferential direction and forms inner side water stopping rings; secondly, tunnel portal outer side water stopping structures are installed, specifically, the portal outer side water stopping structures are installed on theouter sides of the tunnel portal steel rings, and each tunnel portal outer side water stopping structure comprises a rubber curtain cloth and a folding pressing plate; thirdly, sealing grease is filled, specifically, each wate