A method for reducing the construction risk of subway shield tunnel entrance

Abstract

The invention discloses a method for reducing the construction risk of a subway shield tunnel portal. The constructed subway shield tunnel is divided into an excavation excavation section, a main excavation section and a receiving portal excavation section; The segment ring is the front segment ring; when constructing the subway shield tunnel, it includes the following steps: 1. Shield excavation and segment assembly lining construction; 2. Determination of the length of the excavation section of the receiving portal: Measure the length Ln of the tunneling section of the receiving portal; 3. Adjust the length of the tunneling section of the receiving portal; 4. Adjust the length of the tunneling section of the receiving portal: adjust the length of the tunneling section of the receiving portal through the length adjustment ring; 5. Receive Portal segment ring assembly construction; 6. Portal construction. The method of the invention has the advantages of simple steps, reasonable design, low input cost and good use effect, and the embedding length of the door ring can be easily controlled within the allowable range of the design through the pre-processed length adjustment ring.

Description

technical field [0001] The invention belongs to the technical field of subway shield tunnel construction, and in particular relates to a method for reducing the construction risk of a subway shield tunnel portal. Background technique [0002] After the construction of the shield tunnel is completed, the gate ring needs to be removed for the post-construction of the gate structure. The design generally requires that the embedded length L of the portal needs to meet: 400mm≤L≤800mm, and the embedded length of the portal is the distance between the inner side of the portal end wall structure and the starting portal segment ring or the arriving portal segment ring of the shield tunneling tunnel. length. However, in the actual shield tunneling construction, due to various factors such as different thrusts and different tunnel lengths during the excavation process, it is often impossible to ensure that the embedded length of the door ring is just within the allowable range of the ...

AI Technical Summary

Problems solved by technology

However, in the actual shield tunneling construction, due to various factors such as different thrusts and different tunnel lengths during the excavation process, it is often impossible to ensure that the embedded length of the door ring is just within the allowable range of the design. A great construction risk has been increased, and there are corresponding defects and deficiencies in the following aspects: first, the embedded length of the door ring is too short or too long, and the door ring needs to be chiseled out, which will greatly increase the cost compared with directly pulling out the door ring; second 1. When the stratum permits, the embedded length of the door ring exceeds 800mm, and it is considered to remove it. However, due to the large length of removal, the requirements for grouting reinforcement and water sealing at the door position are extremely high. Once the reinforcement and water sealing effect are not good, there will be Larger safety risk; third, when the ground is not allowed, such as the end of the shield tunnel is a sand layer, the groundwater is abundant, and the water is difficult to stop, etc., out of helplessness, we can only communicate with the design to change it to a convex door. Not aesthetically pleasing, but additional costs for communication and design changes

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