tunnel shield assembly and commissioning

Tunnel Shield Assembly and Commissioning Process

Shield assembly and commissioning is the construction process of assembling the disassembled shield machine parts into a whole according to the structural requirements and making them ready for normal use.

Shield assembly and commissioning operations generally include: preparation of the assembly site, laying the rear supporting travelling rails, crane and other assembly equipment into the site, rear supporting trailer assembly down the shaft, installation of the starting platform, shield mainframe assembly down the shaft, installation of the reaction frame and sealing of the hole door, mainframe positioning and connecting with the rear supporting, electrical and hydraulic piping connection, no-load commissioning, installation of the negative ring tube sheet, load commissioning.

Process flow diagram:

Process steps

1. Shield assembly site preparation

The shield assembly site mainly considers the load-bearing capacity of the ground in the crane placing area, if the ground is not strong enough, it needs to be reinforced, and at the same time, the structural dimensions of the shield well are reviewed and the surrounding environment and the approach road are surveyed.

2.Laying of supporting travelling rails after laying

The laying of the track requires that the gauge meets the requirements and is firm and level.

To learn more about tunnel shield machine travelling tracks, please feel free to contact our team for professional advice and customised services.

3. Assembly of the back-up set to go down the well

The back-up set is first assembled into a trailer, and then the trailers are generally lowered into the well in a back-to-front order, such as ‘Trailer No. 5 → Trailer No. 4 → Trailer No. 3 → Trailer No. 2 → Trailer No. 1 → Connecting Bridge’.

After one trailer is lowered into the shaft, it has to be moved back to the designated area by external force such as battery locomotive, and then the next trailer is lowered, which has to be accurately placed on the track.

For the soil pressure balance shield machine, the screw conveyor also needs to be lowered down the shaft, the screw conveyor is long and needs to be lowered down the shaft at an incline, and after being lowered down the shaft, it is placed on the tube sheet car and towed to the designated area for storage.

In practice, sometimes due to the limitations of the starting site, we have to start the shield machine separately, that is, the main machine goes down the shaft first, and the trailer stays on the ground, connected to the main machine through the pipeline, and then the trailer goes down the shaft one after another after the shield is digging.

4. Installation of the starting platform

After the trailer and screw conveyor are in place, the travelling rails at the shaft should be removed and the shield starting platform should be installed.The shield launching platform serves to support the shield mainframe, and it should be precisely positioned before the shield is lowered into the shaft to ensure the correct attitude of the shield when it is launched.

1. Schematic diagram of the starting base

5. Main machine downhole assembly

5.1 For earth pressure balance shield machine

5.1.1 Lowering the main body into the shaft

Use 300 tonnes car crane to move the shield body to the top of the shield well, slowly lower the hook, make it parallel to the starting platform and put it on the starting platform, take off the hook. Then weld the jacking support on the shield shell on both sides of the starting platform, install the jacking support with bolts on the starting platform, and move the shield body to a suitable position by two hydraulic cylinders.

5.1.2 Precursor lowering

The precursor is lowered into the shaft in the same way as the centre body. After being sent to the starting platform, the shield body is moved to a suitable position with the jacking support, and space is reserved for placing the cutter disc after going down the shaft.

Fig. 2 Schematic diagram of shield middle body going down the shaft

Fig.3 Schematic of shield precursor descending into the well

5.1.3 Cutting disc downhole

Hang the wire rope on the cutterhead inlet, use 300 tonnes car crane to unload the cutterhead from the car and put it on the sleeper. Then use 300 tonnes car crane to hold the two lugs to flip the cutter plate up, vertical lifting steadily to 0.5m from the front edge of the shield shaft to stop, and then vertical lifting down the shaft, slowly leaning against the front body. The lower part of the cutterhead is pulled by two guide chains to connect the cutterhead with the front shield; the connecting bolts are installed in place, and the bolts are tightened according to the torque requirement.

5.1.4 Moving the main machine forward

After the cave door is broken, the front shield is moved forward by two hydraulic cylinders, so that the cutter disc is pushed to the palm surface, and then the middle shield is pushed by the cylinders to dock with the front shield, and the connecting bolts are tightened.

5.1.5 Tube sheet installation machine downhole

Installation of the two end beams is carried out after the downhole installation.

Fig.4 Schematic diagram of shield cutter disc going down the shaft

Fig. 5 Schematic diagram of tube sheet installation machine going down the shaft

5.1.6 Shield end lowering

With the cooperation of 300 tonnes and 150 tonnes car cranes, the shield tail was tilted to penetrate into the installer beams and docked with the centre body.

5.1.7 Screw conveyor installation

Extend the laying track to the inside of the shield tail and push the screw conveyor into the shield shell together with the flatbed truck.The front end of the screw conveyor is pulled up with inverted chain, the front end of the screw conveyor is inserted into the inner Nakaton through the hollow of the pipe sheet mounting machine, the flange at the head cylinder of the front end is docked with the forebody, and the coupling bolts are installed.Screw conveyor and the front shield connection sealing installation requirements tight, the mid-body and screw conveyor fixed.

Fig. 6 Schematic diagram of shield tail downhole

Fig.7 Screw conveyor downhole

5.2 For mud-water balanced shields

Shield tail downhole installation

Shield tail descent is the same as soil pressure balance shield, after descending into the well, it is moved to the back edge of the shield well with a cylinder.

Middle shield lowering

The middle shield is lowered into the shaft in the same way as the earth-pressure balanced shield, and then moved back to the shield tail after being lowered into the shaft.

Front Shield Lowering

The front shield is lowered into the shaft in the same way as the earth pressure balance shield, and is moved to a suitable position after lowering, leaving the cutter plate in place.

Cutter disc installation in the lower shaft

The cutter disc is lowered into the shaft in the same way as the earth pressure shield. Install the connecting bolts in the lifting state, apply thread fastening agent to the bolts and tighten them according to the specified force.

Forward movement of the main machine

After the hole door is broken, the front shield is pushed forward by two hydraulic cylinders, so that the cutter plate is topped on the palm surface. Then install the mud pipeline in the centre shield from bottom to top, including each hydraulic ball valve and hydraulic plate valve, then hang down to install the manhole and tighten the connecting bolts according to the specified torque. After completion, the centre shield is moved forward to dock with the front shield and tighten the bolts. Then move forward the tail shield to dock with the middle shield.

6. Installation of the reaction frame

The parts of the reaction frame can be installed in the following assembly sequence:

6.1 Installation of right column

Put the right column into the reserved pit and fix it.

6.2 Install the lower V-beam

The V-beam support is connected to the right column and fixed.

6.3 Left column

After the left column is erected, install the coupling bolts with the V-beam support.

6.4 Upper beam

After lifting and fixing, connect with two columns.

6.5 Steel ring of counterforce frame

Split the steel ring of the counterweight frame into four parts according to the positive point cutting. The lower right part is first connected to the corresponding part of the counterweight frame. The lower left part of the ring is connected to the corresponding part of the counterweight after it is put into position. The upper right part of the ring is lifted up and connected to the corresponding part of the frame. The upper left part of the ring is connected to the corresponding part of the counterweight after it is lifted into position. After the upper left part is installed, the four parts of the ring are welded together with steel plates on the inner arc.

6.6 After the installation work is completed, the measuring team will carry out precise positioning of the counterbalance frame.

Fig.8 Schematic diagram of the reaction frame positioning well

7. Docking of the main machine and the rear set and pipe connection

Lay the rails, move the rear set forward, put the front end of the connecting bridge on the track beam of the tube sheet installer, and then cut off the support of the connecting bridge.Connect the pipelines between the rear kit and the main engine.For mud-water balanced shield structure, connect the slurry feed pipe with pump and the slurry discharge pipe with mud-water separation equipment.

8. Assembly of mud-water separation equipment

The assembly of mud-water balanced shield also includes the assembly of mud-water separation equipment, and the steps are as follows:

(1) Install the mud-water separation equipment submerged tank (as shown in Figure 9)

(2) Installation of vibrating screen (as shown in Figure 10)

Fig.9 Submersible tank of the mud-water separation plant

Fig.10 Installation of mud-water separation equipment vibration

Pre-split screen screen plate installation:

Pre-split screen eccentric motor installation:

Dewatering screen plate installation (as shown in Figure 11)

Fig.11 Dewatering screen plate installation for mud-water separation plant

ig.12 Dewatering screen lifting

Dewatering screen motor installation:

Vibrating screen lifting

Dewatering screen lifting installation

Lift the vibrating screen with a 50t crane at the vibrating screen reinforcement spring plate (Fig. 14). Install it on the upper part of the submerged tank, connected by vibrating springs. (Fig. 13)

Fig.13 Dewatering screen spring connection

Fig.14 Pre-split Screen Lifting Installation

Lifting and installation of the pre-split screen

Lifting is the same as for the dewatering screen. (as in Fig. 14)

(3) Cyclone assembly

Secondary cyclone assembly (Figure 15) in the ground below the assembled steel structure, the secondary cyclone in and out of the cyclone

The main pipeline of the secondary cyclone is placed on the concrete floor, the upper part of the secondary cyclone is installed, lifted and mounted on the steel structure, the lower part of the secondary cyclone is installed, the collection slant pipe of the secondary cyclone is placed in the approximate position, the collection hopper of the secondary cyclone is installed, and the steel structure is lifted and mounted in the correct position. (Figure 16)

Once the collection hopper and collection pipe are in place, the secondary cyclone can be lifted and placed in its position.

Primary cyclone assembly

Fig.15 Secondary cyclone

Assemble the steel structure on the site, install the primary cyclone inlet and outlet combination pipe, install the primary cyclone collection hopper, install the primary cyclone step by step, lift the primary cyclone to the correct part of the steel equipment and fix it, install the lower pipe fittings of the collection hopper, and fix the primary cyclone with the bale hoop.Install the primary cyclone on the steel equipment after the lower part is installed correctly, next install the collection hopper lower pipe.(As shown in Figure 17)

Fig.16 Secondary cyclone assembly on the ground

Fig.17 Primary cyclone installation

Slurry pump, motor installation:

First lifting installation according to the pump suction connection to determine the position of the pump, followed by placing the motor bracket, tight ground bolts, and finally placed the motor fixed.

Installation pulley: adjust the position of motor and pump pulley, install the belt.Installation is completed in Figure 18.

Fig.18 Mud-water separation equipment slurry pump, motor installation completed Figure

9. No-load debugging

After the shield is assembled, it is ready for no-load debugging. The purpose of the no-load commissioning is to check whether the shield system can be normal and turn, for the normal operation of the shield can not be found to find out the reasons. The main commissioning content of soil pressure shield and mud-water shield is slightly different, but roughly the same, mainly is the power distribution system, hydraulic system, lubrication system, cooling system, control system, grouting system, and a variety of instrumentation calibration. The commissioning of mud-water balance shield also includes the commissioning of mud-water separation equipment and slurry modulation system. The commissioning of the mud-water separation equipment includes the operation of the pre-screen vibration motor, the operation of the primary cyclone pump and the primary vibration screen vibration motor, the operation of the secondary cyclone slurry pump and the secondary vibration screen vibration motor, and the connection of the pipelines. Modulation of slurry system debugging content for the mixer, scraper, slurry pump operation, the pipeline connection.

10. Installation of Negative Ring Pipe Sheet

Negative ring pipe sheet needs to be installed in order to transfer the reaction force of the propulsion cylinder to the reaction frame for shield test tunneling.Since there is no sealing requirement for the negative ring, it is possible to install a broken pipe sheet.

11. Load commissioning

After proving that the shield has working ability through the no-load commissioning, load commissioning can be carried out.The main purpose of load commissioning is to check the load capacity of various pipelines, seals and equipment, and to further improve the commissioning work that cannot be completed by no-load commissioning, so as to make the various working systems of the shield structure and its auxiliary systems reach the working state that meets the requirements of normal construction.Usually, the time of trial digging is the time of equipment load debugging.