Method for reducing subway shield tunnel portal construction risks

Abstract

The invention discloses a method for reducing subway shield tunnel portal construction risks. A constructed subway shield tunnel is divided into a starting excavation section, a main body excavation section and a receiving tunnel portal excavation section, and a segment ring in the inner frontmost of the main body excavation section is a front-end segment ring. When used for subway shield tunnel construction, the method includes the steps of firstly, performing shield excavation and segment assembling and lining construction; secondly, determining the length of the receiving tunnel portal excavation section, namely, measuring the length Ln of the receiving tunnel portal excavation section before assembling of the front-end segment ring; thirdly, making judgment on length adjustment of the receiving tunnel portal excavation section; fourthly, adjusting the length of the receiving tunnel portal excavation section through length adjusting rings; fifthly, performing assembling construction on receiving tunnel portal segment rings; sixthly, performing tunnel portal construction. The method for reducing the subway shield tunnel portal construction risks has the advantages that the method is simple in step, reasonable in design, quite low in input cost and good in use effect, and a tunnel portal ring embedding length can be controlled within a design allowance range simply and conveniently by the prefabricated length adjusting rings.

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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