Among the waterproof sealing materials, what sealing materials do we use in shield subway tunnels to achieve the waterproof sealing effect? For sealing materials, water-expandable rubber and non-expandable synthetic rubber that can compress water after swelling with water are generally used. The characteristic of water-expandable rubber seals is that they can make the seal material thinner and improve the sealing effect, and the construction is convenient. Durability is yet to be tested; non-expanded synthetic rubber seals are compressed by elasticity and waterproofed by compressive stress on the contact surface.