Construction method for asynchronous butt joint of shield in ground

Abstract

The invention discloses a construction method for asynchronous butt joint in a shield ground, which is suitable for shield construction engineering of a long-distance tunnel, and comprises the following steps of: firstly propelling a shield to a designed position or temporarily stopping the shield, and arranging a plurality of nearly horizontal freezing pipes by utilizing advanced grouting holes around a shield shell and opening positions on a shield partition plate; a freezing curtain within a certain range is formed in front of a shield through freezing of circulating refrigerants, excavation of soil in front of the shield and around the shield is conducted under the enclosure effect of the freezing curtain, foam concrete is poured to isolate hydraulic connection between the head of the shield and the surrounding stratum, and therefore the internal structure of the advanced shield is dismantled in advance to form the single-head tunnel. And after the following shield starting from the other end is propelled to the butt joint position, the foam concrete at the head of the preceding shield is directly cut through a cutter head until the following shield is propelled to the interior of the preceding shield, and after receiving and disassembling of the following shield are completed, all tunnels are communicated. According to the method, the construction process of asynchronous butt joint in the shield ground is achieved, the mutual influence between construction of two shield machines can be reduced, the construction cost is saved, and the construction time is shortened.

Description

Technical Field

[0001] The invention relates to a shield underground asynchronous docking construction method, which is applicable to the shield construction field of long-distance tunnels in water-containing soft soil layers. Background Art

[0002] During the construction of urban underground projects, when the length of the tunnel is long, in order to shorten the construction time, two shield machines are often used to excavate towards each other underground to the joint, and the strata are improved by grouting or freezing at the joint position of the two shields to close the joint between the two shields, so as to connect the two shields together and dismantle the internal structure to achieve long-distance tunnel construction. In the current construction method, only after the two shield machines have excavated to the joint position can grouting or freezing be carried out simultaneously at the joint position to close the joint between the two shield machines and achieve the construction conditions for dismantling the internal structure of the shield. Therefore, the construction status of the two shield machines will affect the shield docking construction process. The internal structure of the shield can only be dismantled after the two shields are docked, resulting in a long overall construction time for the shield docking, high construction costs, and a great impact on the surrounding environment during the construction process. Summary of the invention

[0003] In view of the shortcomings of the existing technology, a construction method for asynchronous docking of shield machines in the ground is provided, which uses the method of freezing and reinforcing the ground to excavate the ground, and pours a foam concrete structure at the head of a single shield machine. The foam concrete is used to separate the construction processes of the two shield machines, so that the two shield machines can be excavated to the joint position at different times, and the internal structures of the shield machines are dismantled respectively to complete the construction process of asynchronous docking of the shield machines in the ground. In this way, there is no need to consider the coordination relationship between the construction process of the two shield machines. The two shield machines are constructed independently, and the internal structures of the shield machines are dismantled separately, which facilitates the organization of the shield construction process and shortens the duration of the enclosure structure.

[0004] To achieve the above technical objectives, the present invention provides a construction method for asynchronous underground docking of shield machines, in which a leading shield machine that is constructed first is advanced to the shield docking position, and a frozen curtain formed in front of the shield machine by a freezing method is used to provide support, and foam concrete is poured after excavation of the stratum. The freezing is stopped when the strength of the foam concrete meets the requirements, and the foam concrete is used to isolate the leading shield machine from the surrounding strata. The internal structure of the leading shield machine can be dismantled to form a single-ended tunnel structure. After the following shield machine is advanced to the foam concrete position, the cutter head is directly used to cut the foam concrete and advance into the interior of the leading shield machine. After the internal structure of the following shield machine is dismantled, the tunnel penetration construction can be achieved.

[0005] Furthermore, all the freezing pipes that form the frozen soil curtain in front of the advance shield are constructed inside the shield. The grouting holes and geological exploration holes reserved on the shield structure are used to arrange the freezing pipes in a nearly horizontal manner. The length of the freezing pipes is determined according to the range of the required freezing curtain. If necessary, the internal structure of the shield can be partially penetrated to increase the arrangement of some freezing pipes to strengthen the freezing effect. All freezing pipes are constructed inside the shield and do not require a ground construction environment. Therefore, the construction method can be adapted to strata below the water surface of rivers, lakes, and seas.

[0006] Furthermore, to meet the needs of direct cutting of freezing pipes by the following shield machine, the freezing pipes can be made of plastic, aluminum alloy and other materials, and can be frozen using liquid nitrogen ultra-low temperature methods to speed up the freezing process and further shorten the construction time.

[0007] Furthermore, under the protective effect of the frozen soil in front of the shield, the stratum in front of the shield is excavated to form a certain space, so that foam concrete is poured around the shield head to isolate the hydraulic connection between the shield and the surrounding strata, and to build a normal pressure construction environment inside the shield. At this time, the freezing construction can be stopped. The main purpose of using foam concrete is to meet the needs of direct cutting by the subsequent shield cutter head, and the thickness and range of foam concrete pouring are based on balancing the water and soil pressure outside the shield.

[0008] Furthermore, under the condition that the foam concrete isolates the external hydraulic connection of the shield, the internal structure of the first shield can be dismantled in advance to form a dead-end tunnel, and the end of the tunnel is poured foam concrete. Since the foam concrete can isolate the external hydraulic connection of the shield, the formed dead-end tunnel can remain stable for a long time, waiting for the subsequent shield to advance to the docking position, without taking other construction measures.

[0009] Furthermore, the subsequent shield starts construction from the opposite direction, and the specific start time of construction is not affected by the construction of the preceding shield. The diameter of the subsequent shield is slightly smaller than that of the preceding shield to ensure that the subsequent shield can drill into the interior of the preceding shield. The subsequent shield has the ability to directly cut frozen pipes and foam concrete with the cutter head, thereby achieving direct excavation into the interior of the preceding shield.

[0010] The specific steps are as follows: a. The leading shield machine shall start excavation construction first until it reaches the docking position. The specific docking position can be a pre-designed position or an emergency stop position in case of failure during shield excavation; b. Using the grouting holes and geological exploration holes of the previous shield shell, multiple nearly horizontal freezing pipes are arranged inside the shield. The freezing pipes are made of plastics, alloys and other materials that can be directly cut by the shield, and low-temperature refrigerants such as liquid nitrogen are circulated inside the freezing pipes, thereby forming a freezing curtain in front of the shield; c. Under the protection of the frozen soil curtain in front of the shield, the ground space is excavated and foam concrete is poured in the excavated space, so as to isolate the hydraulic connection with the external ground at the head of the shield. When the strength of the foam concrete meets the requirements of bearing and water sealing, the freezing construction can be stopped; d. Under the protection of the foam concrete at the head of the advance shield machine, the internal structure of the advance shield machine is dismantled to form a dead-end tunnel; e. Later, the rear shield that starts construction from the opposite direction advances to the foam concrete position, directly cuts the concrete and enters the interior of the leading shield, completes the reception construction of the rear shield, and dismantles the rear shield to form a through tunnel structure.

[0011] Beneficial effect: By excavating the stratum and pouring foam concrete under the protection of the freezing curtain formed by freezing, the construction process of the two shields can be completely isolated. The construction of the two shields can be organized separately without considering the order of construction between the two. The leading shield and the succeeding shield can be asynchronously advanced to the docking position and disassembled and constructed separately, thereby ensuring the continuous construction of the succeeding shield. There is no need to wait until the two shields are advanced to the docking position before conducting stratum reinforcement and docking construction. Therefore, the shield docking construction time can be shortened and construction costs can be saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of asynchronous docking construction in the shield tunneling according to an embodiment of the present invention.

[0013] In the figure: 1-advance shield; 2-freezing pipe; 3-internal structure; 4-foam concrete; 5-freezing curtain; 6-rear shield. DETAILED DESCRIPTION

[0014] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0015] like Figure 1 As shown, a construction method for asynchronous docking of shield machines in the ground of the present invention is that the leading shield machine 1 starts construction first, and when it is advanced to the docking position, the shield machine is stopped, and a plurality of nearly horizontal freezing pipes 2 are arranged inside the leading shield machine 1 by utilizing the grouting holes and geological exploration holes on the shell of the leading shield machine 1, and a low-temperature refrigerant such as liquid nitrogen is circulated in the freezing structure pipes 2, so as to quickly form a freezing curtain 5 in front of the leading shield machine 1; under the enclosing effect of the freezing curtain 5, the stratum in front of the leading shield machine 1 is excavated, and the freezing pipes in the excavated space are cut off, and foam concrete 4 is poured in the formed space, and the freezing can be stopped after the strength of the foam concrete 4 meets the conditions for bearing the external water and soil pressure.

[0016] Under the protection of the foam concrete 4, the internal structure 3 of the leading shield 1 is dismantled to form a dead-end tunnel together with the constructed tunnel; after the rear shield 6 is advanced to the position of the foam concrete 4, it directly cuts the foam concrete 4 and drills into the leading shield 1, and through the dismantling of the internal structure of the rear shield 6, the overall penetration of the tunnel is achieved.

[0017] During construction, the freezing curtain range can be designed according to the differences in shield structure, diameter, and burial depth, so that different numbers of near-horizontal freezing pipes can be arranged at different locations, and the length and freezing time of the freezing pipes can be adjusted to meet the needs of balancing external water and soil pressure during stratum excavation. The construction method of asynchronous docking of shields in the ground can adjust the construction time of the leading and trailing shields at any time, facilitate the organization of the construction process, do not require ground construction conditions, and can reduce the volume of frozen soil at the shield docking position, inhibit the impact on the environment during the freezing construction process, save construction costs, and reflect significant economic and social benefits.

Claims

1. A construction method for asynchronous docking of shield tunneling in the ground, characterized by: A closed freezing curtain (5) is formed in front of the leading shield (1) by using a plurality of nearly horizontal freezing pipes (2) arranged inside the leading shield (1). Under the protection of the freezing curtain (5), the ground is excavated and foamed concrete (4) is poured. After the foamed concrete (4) wraps around the head of the leading shield (1) and forms strength, freezing is stopped and the internal structure (3) of the leading shield (1) is dismantled to form a dead-end tunnel. After the rear shield (6) excavated from the opposite direction is advanced to the docking position, the foamed concrete (4) is directly broken by cutting with a cutter head and the front shield (1) is drilled into after it has been dismantled. After the internal structure (3) of the rear shield (6) is dismantled, the tunnel can be penetrated. The plurality of sub-horizontal freezing pipes (2) are constructed inside the leading shield (1), and are drilled using the advance grouting holes around the casing of the leading shield (1) and the reserved exploration holes on the panel of the leading shield (1). The freezing pipes (2) are made of a plastic pipe that can be directly cut by the cutter head of the trailing shield (6). The length of the freezing pipes (2) is adjusted according to the range of forming the freezing curtain (5), and liquid nitrogen ultra-low temperature rapid freezing is used to quickly form the required freezing curtain (5) in front of the leading shield (1). The start time of the excavation construction of the trailing shield (6) can be adjusted freely without considering the construction progress of the leading shield (1). The trailing shield (6) can directly cut the foam concrete (4) and enter the interior of the leading shield to complete the dismantling construction of the trailing shield (6). It is not required to synchronously dock the leading shield (1) and the trailing shield (6) before carrying out the shield docking construction.

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