Protection method for upper span structure of subway shield tunneling in liquefied soil with ultra-close open excavation

Abstract

The present invention discloses a method for protecting an open-cut upper span structure of a subway shield in liquefied soil at an ultra-close distance, and provides an implementation method capable of controlling the deformation of an existing shield in a soft liquefied soil layer that is extremely sensitive to construction vibrations to meet the safety requirements of an operating subway track. The invention is a multi-technical combination, safe and reliable shield protection method, which mainly includes the comprehensive use of a variety of technical means such as an "M"-shaped MJS reinforcement body, a top-pushing steel pipe curtain (internal grouting), and a "bench structure" to complete the protection of an existing shield section under a liquefied soil layer in a three-in-one manner, thereby meeting the safety requirements of an operating subway.

Description

Technical Field

[0001] The invention belongs to the technical field of underground building construction, and in particular relates to a method for protecting an upper span structure of an open cut implemented by a subway shield in ultra-close distance in liquefied soil. Background Art

[0002] With the development of cities, underground rail transit has become a common public transportation measure in major cities. With the further advancement of urban construction, the construction of new tunnels, sunken plazas and other underground buildings above the operating subway shield will become more and more frequent. In the existing similar cases, the new underground structure is generally far away from the existing shield or the geological conditions are better. It is extremely rare in China to build a new underground structure at a very close distance (the closest distance is no more than 2m) above the shield in the soft liquefied soil layer. In the above situation, the use of conventional protection methods cannot ensure the safety of the operating subway, and the use of a three-in-one multi-technical comprehensive protection measure can effectively meet the safety requirements of ultra-close construction above the subway shield under extremely poor geological conditions. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for protecting the upper span structure of an open cut implemented at an ultra-close distance by a subway shield in liquefied soil, that is, to provide a safe and reliable method for protecting underground structures constructed at an ultra-close distance above an operating subway shield in a soft liquefied soil layer (or similar extremely poor geological conditions), to provide guidance for similar projects in the future, and to solve the deficiencies in the prior art.

[0004] In order to achieve the above object, the object of the present invention is achieved through the following technical solutions:

[0005] A method for protecting an upper span structure of a subway shield tunnel in liquefied soil at an ultra-close distance is provided, comprising the following steps:

[0006] Working pits are constructed on both sides of the subway shield tunnel section, and supporting piles are set up at the bottom of the working pits;

[0007] Constructing an MJS reinforcement body located above the subway shield section, wherein the MJS reinforcement body is in an "M" shape, and the subway shield section is located in the hole of the "M"-shaped structure of the MJS reinforcement body;

[0008] constructing engineering piles, wherein the engineering piles are erected between subway shield sections;

[0009] Before the MJS reinforcement body is fully strengthened, the construction of the top-pushing steel pipe curtain is completed, the top-pushing steel pipe curtain passes through the top of the MJS reinforcement body, and the axial direction of the top-pushing steel pipe curtain is perpendicular to the axial direction of the engineering pile; and,

[0010] After the MJS reinforcement body reaches the required strength, a new underground structure bottom plate is excavated and constructed on the top section of the MJS reinforcement body. The new underground structure bottom plate, the engineering piles and part of the supporting piles of the working pit form a bench structure, and a counterweight is applied above the bench structure.

[0011] For example, in the method for protecting the upper span structure of an open cut implemented by a subway shield at an ultra-close distance in liquefied soil, a retarder is added during the construction of the MJS reinforcement body.

[0012] For example, in the method for protecting the upper span structure of an open cut implemented by a subway shield at an ultra-close distance in liquefied soil, after the construction of the jacking steel pipe curtain is completed, cement slurry or superfluid fine stone concrete is injected into the jacking steel pipe curtain.

[0013] The beneficial effects of the technical solution of the present invention are:

[0014] The present invention provides an implementation method capable of controlling the deformation of an existing shield in a soft liquefied soil layer that is extremely sensitive to construction vibrations to meet the safety requirements of an operating subway track. The present invention is a shield protection method that combines multiple technologies and is safe and reliable. The method mainly includes the comprehensive use of a variety of technical means such as an M-shaped MJS reinforcement body, a top-pushing steel pipe curtain (internal grouting), and a "bench structure" to complete the protection of the existing shield section under the liquefied soil layer in a three-in-one manner to meet the safety requirements of an operating subway. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To further illustrate the above-mentioned objectives, structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0016] Figure 1 This is a node cross-sectional diagram of the subway shield protection measures in the liquefied soil layer of a preferred embodiment of the present invention;

[0017] Figure 2 This is a node plan view of the subway shield protection measures in the liquefied soil layer of a preferred embodiment of the present invention;

[0018] Figure 3 This is a cross-sectional view of the MJS reinforcement, steel pipe curtain and bench structure comprehensive protection above the shield in a preferred embodiment of the present invention;

[0019] In the figure: 1. Metro shield section; 2. Working shaft; 3. Support piles; 4. MJS reinforcement body; 5. Engineering piles; 6. Push-up steel pipe curtain; 7. New underground structure bottom plate; 8. Counterweight. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0021] See also Figure 1 , Figure 2 and Figure 3 As shown, the protection method of the upper span structure of the subway shield in the liquefied soil at an ultra-close distance includes the following steps: firstly, a working well 2 is constructed on both sides of the subway shield section 1, and a supporting pile 3 is set up at the bottom of the working well 2; an MJS reinforcement body 4 is constructed above the subway shield section 1, and the MJS reinforcement body 4 is "M"-shaped, and the subway shield section 1 is located in the hole of the "M"-shaped structure of the MJS reinforcement body 4; engineering piles 5 are constructed, and the engineering piles 5 are erected between the subway shield sections 1; and the MJS reinforcement body 4 is not Before the strength is fully formed, the construction of the top-pushing steel pipe curtain 6 is completed. The top-pushing steel pipe curtain 6 passes through the top of the MJS reinforcement body 4, and the axial direction of the top-pushing steel pipe curtain 6 is perpendicular to the axial direction of the engineering piles 5; and after the MJS reinforcement body 4 reaches the strength, a new underground structure bottom plate 7 is excavated and constructed at the top section of the MJS reinforcement body 4. The new underground structure bottom plate 7 forms a bench structure with the implemented engineering piles 5 and some supporting piles 3 of the working wells 2 on both sides, and a counterweight is applied above the bench structure. The specific size of the counterweight 8 shall be based on the actual construction environment.

[0022] In the preferred embodiment, a retarder is added during the construction of the MJS reinforcement body 4 to ensure the smooth implementation of the jacking steel pipe curtain 6 and to combine with the MJS reinforcement body 4 to form an integrated protection measure.

[0023] After the construction of the top-pushing steel pipe curtain 6 is completed, cement slurry or superfluid fine stone concrete is injected into the top-pushing steel pipe curtain 6 to increase the bending rigidity of the steel pipe curtain.

[0024] The present invention provides an implementation method capable of controlling the deformation of an existing shield in a soft liquefied soil layer that is extremely sensitive to construction vibrations to meet the safety requirements of an operating subway track. The present invention is a shield protection method that combines multiple technologies and is safe and reliable. The method mainly includes the comprehensive use of a variety of technical means such as an M-shaped MJS reinforcement body, a top-pushing steel pipe curtain (internal grouting), and a "bench structure" to complete the protection of the existing shield section under the liquefied soil layer in a three-in-one manner to meet the safety requirements of an operating subway.

[0025] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for protecting the upper span structure of a subway shield machine in liquefied soil at an ultra-close distance, characterized in that: The steps include: Working shafts (2) are respectively constructed on both sides of a subway shield tunnel section (1), and support piles (3) are set up at the bottom of the working shafts (2); Constructing an MJS reinforcement body (4) located above the subway shield section (1), wherein the MJS reinforcement body (4) is in an "M" shape, and the subway shield section (1) is located in a hole of the "M"-shaped structure of the MJS reinforcement body (4); Constructing engineering piles (5), wherein the engineering piles (5) are erected between the subway shield sections (1); During the construction of the MJS reinforcement body (4), a retarder is added, and before the MJS reinforcement body (4) has fully developed strength, the construction of the top-pushing steel pipe curtain (6) is completed, the top-pushing steel pipe curtain (6) passes through the top of the MJS reinforcement body (4), and the axial direction of the top-pushing steel pipe curtain (6) is perpendicular to the axial direction of the engineering pile (5); and, After the MJS reinforcement body (4) reaches a certain strength, a new underground structure bottom plate (7) is excavated and constructed on the top section of the MJS reinforcement body (4). The new underground structure bottom plate (7) forms a bench structure with the engineering piles (5) and some supporting piles (3) of the working well (2), and a counterweight is placed on top of the bench structure.

2. The method for protecting the upper span structure of a subway shield tunnel in liquefied soil at an ultra-close distance according to claim 1, characterized in that: After the construction of the jacking steel pipe curtain (6) is completed, cement slurry or superfluid fine stone concrete is injected into the jacking steel pipe curtain (6).

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