Keywords

1 Introduction

The TBM must be dismantled after the completion of the construction of the TBM, taking Lot of Beijing New Airport Line as an example, the shield construction uses two Φ9040 mm EPB TBM from China Railway Engineering Equipment Group Co., Ltd. For construction. The screw machine weighs about 55 T and must be dismantled in the tunnel, dismantled tooling will be build in tunnel, and it is difficult to control risks in the tunnel and demolition process. The shield main machine and the shield receiving frame weigh about 870 T and must be translated to the disassembly area for dismantling, and it is difficult to make translation tooling and control the translation process. Gantries retreated to the launching shaft, and the retreat distance is about 3.6 km, and it is difficult to dismantle and retreat. In view of the difficulties in the construction process of the project, such as the demolition of the screw machine, the translation of the main engine, and the retreat of the trailer, the key technologies are studied.

2 Dismantling Sequence of TBM

After the TBM breaking throughout, it is prepared for shutdown, and then the belt of the belt conveyor is cut. Disconnect the high-voltage electricity, retract all thrust cylinders, discharge the hydraulic oil in the main hydraulic tank and the gear oil in the main drive and the water in the system, etc. [1]. Disconnect Gantry1 and erector, and then move Back-up system backward 30, reserving space for dismantling screw conveyor, and the disassembly flow chart [2] (as shown in Fig. 1).

Fig. 1.
figure 1

Sequence of TBM disassembly

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3 Research on Key Technologies for the Main Machine

There are two main technical difficulties when removing the main machine, â‘ Demolition technology of screw conveyor in tunnel translation technology of main machine.

3.1 Demolition Technology of Screw Conveyor in Tunnel

Design Removal Tooling for Screw Conveyor

The large-diameter screw conveyor weighs about 55 tons, and due to the space constraints for demolition in the tunnel, the demolition tooling had to be made in advance [3] (as shown in Fig. 2).

Fig. 2.
figure 2

Screw conveyor removing tooling

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Since the tooling is used in the tunnel, the transportation space is limited, so the individual parts are prepared in advance and then welded in the tunnel as a whole. Part2 is welded to the beam of the assembly machine, the overall width of the fixture is 2810 mm, the height is 3000 mm, and the angle of tilting fixed support is 65°(as shown in Fig. 3). Part3 is welded to the flat plate, the overall width of the fixture is 2200 mm, the height is 6630 mm, and the angle of inclined fixed support is 75°. The width of the vertical beam is 1600 mm, and the maximum φ of the screw machine parts is 1400 mm, which can pass through the screw machine. Through the calculation of the force, the main beam of the tooling is made of HW300 section steel, and the material is S355JR (as shown in Fig. 4).

Fig. 3.
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Demolition tooling of lifting pint 2

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Fig. 4.
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Demolition tooling of lifting piont3

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Description of the Screw Conveyor Dismantling Process

During the dismantling of the screw conveyor, 3 lifting points are set up, lifting points 2 and 3 use 4 × 20 T chain hoists respectively, and lifting point 1 uses 2 × 10 T chain hoists. When the screw conveyor is slowly pulled out, move the trolley of lifting point 3 backwards, so that the center of gravity of the screw conveyor cannot exceed the top force point of lifting point 3 [4]. After the screw shaft completely leaves the front shield body, release the chain hoist at lifting points 2 and 3 to make the front part of the screw conveyor fall, and at the same time continue to tighten the chain hoist at lifting point 1 to make the tail of the screw conveyor continue to lift (as shown in Fig. 5).

Fig. 5.
figure 5

Lift screw conveyor out of front shield

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When adjusting the attitude of the screw conveyor is close to the horizontal state, and the height exceeds the rotary structure of the erector by about 100 mm, use the support to fix the screw machine support on the transport trolley (as shown in Fig. 6). The chain hoist is removed and the screw conveyor is transported to launching shaft for lifting.

Fig. 6.
figure 6

Pulling out process of screw conveyor

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3.2 Main Machine Move and Dismantle

Design Moving Tooling for Main Machine

First, four rows of single 3050 × 625 × 40 mm steel plates are laid on the concrete floor, and the dovetail grooved design is carried out at both ends of each steel plate [5] (as shown in Fig. 7), so that the connection between the steel plates is firmer, and the total laying length of the single row is 51.85 m (as shown in Fig. 8).

Fig. 7.
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Steel plate

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Fig. 8.
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Steel plate laying

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Calculate Force for Moving Main Machine

The large-diameter TBM main machine weighs about 820 tons, and the shield receiving frame weighs about 50 tons. The shield translation force supporting carriers are connected to the steel plate using M30 × 60–12.9 bolts, the preload of the bolt is 432.5 kN, each reaction support seat has a total of 12 bolts (as shown in Fig. 9), and 2 reaction supporting carriers are used when the main engine translation[6].

Fig. 9.
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Connection between reaction support seat and steel plate

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According to the working conditions, take the friction coefficient of the supporting carriers and the steel plate u = 0.1. The friction force ƒ1 when the shield is moved, and two cylinders with thrusting force 200 T and stroke of 1000 mm are used when the shield body is moved;

$$ \begin{gathered} f{1} = {\text{G}} \times {\text{u}} \hfill \\ f{1} = {87}0\,{\text{kN}} \hfill \\ \end{gathered} $$

The friction generated when the main machine slides with the shield receiving frame is 870 kN, and the thrust of the cylinder meets the requirements of the main machine moving.

The friction generated by the pretension between the reaction support seat and the steel plate connecting bolt is Æ’2;

$$ \begin{gathered} f{2} = {2} \times {12} \times {\text{u}} \times {432}.{5}\,{\text{kN}} \hfill \\ f{2} = {1}0{38}\,{\text{kN}} \hfill \\ f{2} > f{1} \hfill \\ \end{gathered} $$

In the case that the bolt does not bear the shear force, the friction generated between the reaction supporting carriers and the steel plate can meet the working conditions of shield moving.

Main Machine Moves Process

Install the translation cylinder and reaction support seat, and push forward the receiving frame of the TBM pushed by the cylinder [7] (as shown in Fig. 10). Two cylinders push the receiving frame, and the cylinder rod is retracted when each cylinder stroke is about 800 mm, and then the cylinder is retracted to dry forward and the jacking supporting carriers are retracted, and the main machine is translated to the disassembly area after repeated pushing.

Fig. 10.
figure 10

Main machine moving

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Main Machine Removal and Precautions

After the main machine is moved to the disassembly area, use the crane to lift out the shield blocks one by one, and disassemble each part of the main machine according to the disassembly sequence of the main machine. Note other items during the removal of the main machine;

  1. 1)

    In order to reduce the disassembly time, some connecting bolts between the cutter head and the main drive M48-10.9 can be removed in advance. The weight of the cutter head is 95 T. By calculation, there are 16 bolts reserved, such as top, bottom, left and right respectively. The pretight force of M48-10.9 is F1 = 1050 kN, and the friction generated by the connection bolts between the main drive and the cutterhead is like cosmos.

    $$ f{1} = {\text{F1}} \times {\text{u}} \times {16} = {168}0\,{\text{kN}} > {95}0\,{\text{kN}} $$
    (1)

    By calculating that the friction force generated by the connecting bolt between the main drive and the cutterhead is about 1.8 times of the cutter head weight, it can meet the requirements of full operation.

  2. 2)

    Since the overall weight of the articulation ring and the thrust cylinders exceeds the lifting capacity of the crane, the grippers of the thrust cylinder is removed first when the main machine is disassembled, and then the thrust cylinder is pulled out one by one. The thrust cylinders is removed in two stages. The upper thrust cylinders are removed first, and the lowerthrust cylinders are removed after the erector is removed.

4 Research on Gantries Removal and Backing Technology

4.1 Gantries Removal Special Tooling Design

Gantries Tooling Design and Manufacture

In the dismantling of the Gantries, the connecting pins should be removed first. At the same time, 4 supporting seats should be welded on the main vertical beam of the Gantry (as shown in Fig. 11). Use a jack to lift the Gantry 100 mm [8].

Fig. 11.
figure 11

Gantry supporting structure

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Force Calculation of Gantry Supporting Beam

According to the supporting force of Gantry on the muck truck, the model was simplified into a simple beam stress model (Fig. 12). F1 = F2 = 17.5 T was calculated, and L1 = L3 = 320 mm and L2 = 2270 mm were obtained according to the structure of the muck truck.

Fig. 12.
figure 12

Simple beam model

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According to the law of balance of couples.

$$ {\text{F}}1 \times ({\text{L}}1 + {\text{L}}2) - {\text{F}}3 \times {\text{L}}2 = {\text{F}}2 \times {\text{L + }} $$
(2)
$$ {\text{F}}3 \times ({\text{L}}3 + {\text{L}}2) - {\text{F}}4 \times {\text{L}}2 = {\text{F}}1 \times {\text{L}}1 $$
(3)

So F3 = F4 = 17.5 T, that is, the pressure of the support seat against the beam is 17.5 T.

SolidWorks was used to build a three-dimensional model, and the model was divided into grids and loaded with 175 kN by external force. The calculation results were obtained through finite element analysis (Fig. 13).

Fig. 13.
figure 13

Results of finite element analysis

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Through finite element analysis, the maximum force of the beam is about 300 MPa, and the material of the beam is Q355B, so it can meet the requirements of the Gantry support strength.

4.2 Gantries Move Backward

After the Gantry is jacked up, the locomotive drives the muck car to move to the bottom of the Gantry, and the muck car beam is supported under the support seat, and then the jack is unloaded and the Gantry support seat is supported on the beam. Then the locomotive drives the Gantry slowly. When the Gantry is driving, an observer is set before and after the locomotive to pay attention to the posture of the Gantry at all times.

5 Conclusion

By analyzing and summarizing the dismantling process of two soil pressure balancing TBM with Φ9040 mm in Sect. 6 of Beijing New Airport Line, the following conclusions are drawn.

  1. 1.

    The combination of muck car formation and special tooling can safely, efficiently and quickly solve the problem of long-distance retreat of Gantries;

  2. 2.

    The dismantling of screw screw tunnel is the risk point. The screw conveyor weighing about 55 T can be safely dismantled in the tunnel through the dismantling tools welded on flat car and chain block;

  3. 3.

    When the main machine is translated, the bottom of the shield receiving frame is laid with steel plate. The reaction support seat and the jacking cylinder can be used to solve the translation problem of the large diameter shield main machine efficiently and quickly.

The successful implementation of the project has accumulated rich construction experience for dismantling TBM in the tunnel.