1 shield overview
The articulated EPB shield produced by Komatsu Company of Japan was used in the construction of the tunnel between the Summer Palace and Yuanmingyuan on Beijing Metro Line 4. It will cross the gravel composite stratum, with a propulsion distance of about 1.5km, and the main parameters of the shield are: diameter: Ф 6140 mm; Length: 8570mm Propulsion speed: 0 ~ 8.5 cm/min; Total thrust: 37730kN. The functions and characteristics of the main components of articulated EPB shield are as follows:
(1) The cutterhead is driven by 9 cutterhead motors, and then controlled by 5 frequency converters to realize the selection and switching of cutterhead speed. The cutter head speed has five steps, namely, 0.5, 0.7, 1. 1, 1.6 and 2.2r/min.
(2) The screw machine is driven by 1 hydraulic motor, and stepless speed regulation can be carried out through proportional valve. The speed regulation range of the screw machine is 0~25r/min.
(3) The screw machine has telescopic function. During maintenance, the screw shaft can be retracted, and the front two screw gates can be closed to completely isolate the screw from the mud bin.
(4) The propulsion system is driven by a propulsion pump, 22 propulsion jacks are divided into four zones, and the oil pressure is controlled by a proportional valve to adjust the propulsion speed.
(5) In the articulated system, the articulated pump drives four articulated jacks to rotate up and down, left and right, and fully expand and contract, so as to adjust the propulsion posture of the shield.
(6) There are 1 hydraulic pumps for assembling revolving doors and spiral doors, which are used for assembly/propulsion respectively.
(7) Before the belt conveyor runs, give an alarm for 5s before it can be officially put into operation. There are pull rope emergency stop buttons on both sides of the belt conveyor, which can stop the belt conveyor urgently.
(8) There are two seals before and after the shield tail grease, and 1 each seal pump of the shield tail grease is injected at 6 points.
(9) There are two centralized lubricating grease pumps (hereinafter referred to as grease pumps) to inject grease under continuous and intermittent working conditions respectively.
(10) There are 1 thin oil lubrication circulating pumps (circulating pumps for short) for lubricating oil filling.
(1 1) Use two mud pumps to adjust the mud addition flow through frequency converter. Add mud to the soil tank.
(12) The grouting system composed of grouting pump and mixer can be used for single grouting and has the function of cleaning pipes.
(13) There are 1 foam devices, which can inject foam into the soil in front of the shield.
2 shield measurement and control system
2. 1 shield control system
The shield control system is mainly composed of PLC programmable controller and display operation terminal. PLC adopts master-slave structure, with 1 master station and 2 slave stations, and another set of grouting PLC.
The PLC programmable controller adopts Ans series products produced by Mitsubishi Corporation of Japan. The A2USHCPU component used in this shield is one of the most advanced miniaturized PLCCPU in the world. It uses Mitsubishi sequential control processor (MSP), which makes it comparable to many large and more expensive PLCs in speed and function.
The PLC master station is located in the console. The main CPU model is A2USHCPU-S 1, and the three display operation terminals are numbered GC 1, GC2 and GC7. Among them, GC 1 and GC2 operate shielding devices respectively, which are standby for each other. Another GC7 operates the mud adding equipment.
1# The slave station is located in the shield and has three display operation terminals numbered GC3~5. Among them, GC3 and GC4 operate shield jacks, and GC5 remotely operates grouting. 2# slave station is located in 2# frame, equipped with 1 display operation terminal (commonly known as touch screen), numbered GC6, to operate grouting equipment.
The master station is connected with 1# and 2# slave stations through two parallel cable loops (double loop network). The system adopts high-speed and reliable data communication, namely MELSECNET/Ⅱ data communication system, and uses two parallel cable loops to connect PLC stations, one of which is called forward loop (or main loop) and the other is called reverse loop (or secondary loop). When the cable in the main loop breaks, the communication automatically switches to the auxiliary loop to continue data communication. If both loops are interrupted or disconnected, the connected stations will continue to communicate except the interrupted PLC.
Grouting PLC is independent of PLC system, and its model is FX 1N-40MR. It exchanges signals with PLC master station through I/O port.
PLC is equipped with switch input/output components, analog input/output components, communication interface components and computer communication components. See table 1PLC configuration table for details.
2.2 Attitude Measurement and Control System
The attitude measurement and control system of shield consists of shield and ground. The shielding part is mainly composed of total station, prism, measuring interface, control unit, computer (display) and other equipment. The ground part is mainly composed of a computer (display) and a hub, and the shielding and ground parts are connected by a pair of megabit modems (SDSL). See figure 2.
The system realizes the automatic measurement of shield posture through high-precision measuring instruments and special software, and can obtain the following real-time data information:
(1) coordinates and login name of the back viewpoint, station;
(2) measuring the data of the target;
(3) when measuring the dip angle and rotation angle of the shield;
(4) Calculation results of coordinate values and azimuth deviation before and after shield.
In the shield, the attitude signal measured by the total station and the shield construction signal obtained by PLC are integrated in the measurement interface unit, displayed on the shield computer display and sent to the ground computer.
2.3 detection system
According to the requirements of the measurement and control system of the shield, the basic detection instruments are configured, and the analog signals to be detected include: earth pressure of the earth bin, oil pressure of the propelling jack, stroke and speed, four-zone oil pressure, oil pressure of the screw machine, rotation speed, stroke of the articulated jack, output power of the cutter head inverter, sealing temperature of the cutter head, gate opening of the screw machine, grouting pressure, slurry level of the grouting cylinder, foam pressure, mud adding pressure, mud adding flow, slope and angle of the shield. There are more than 40 groups of sensors (transmitters) * * *, as shown in Table 2.
In addition, more than 60 limits and more than 10 pressure relays are configured to detect switching signals. It mainly detects the left/right limit state of assembly machine rotation, the left/right limit state of assembly machine cable reel, the expansion and contraction state of screw machine, the opening and closing state of screw machine gate, the opening and closing state of air valve, mud filling valve, grouting valve, shield tail sealing valve, grease level of centralized lubrication, grease level of shield tail, etc. , centralized lubrication grease pump and pipeline pressure high/low, shield tail seal oil pressure high or low.
2.4 Shielding Control and Operation
2.4. 1 shielding control
The main controls of shield are: earth pressure balance control, sequence control and logic control.
① Balance control of earth pressure is the main control of shield machine. When the earth pressure in the silo changes due to the disturbance of the front soil, there will be a deviation value between it and the set value. By automatically controlling the rotating speed of the screw machine, the earthwork output can be adjusted, so that the earth pressure in the soil bin can reach the dynamic balance of the set value, and the deviation value can be reduced.
(2) Sequence control is to make the propulsion equipment run in the normal working order in the propulsion state, combined with control conditions such as time sequence and logic: cooling pump operation → lubricating pump operation → cutter head rotation → spiral gate opening → belt conveyor rotation → screw machine rotation → propulsion jack action. Operation out of sequence will not make the shield work normally.
(3) Logical control is to shield the control of each device according to a specific logical relationship. For example, when advancing, if the cutter head torque is overloaded or the screw machine is reversed, or the advancing speed is too fast or the earth pressure exceeds the upper limit, the extending action of the advancing jack will stop according to the logical conditions. Another example is that the hinge pump operates normally, the cutter head rotates normally, and when the hinge angle is within the normal range, the hinge must be controlled by rotating up and down, left and right, fully extending and fully retracting. When a certain condition does not exist, the hinge control ends immediately.
Interlocking condition is indispensable for shield control, and all equipment in shield involves interlocking condition. For example, the power supply is connected reversely, and the PLC communication fails, so all the equipment can't work. The actions of some devices are interlocked, for example, when the front door is opened and closed, it is impossible to control the expansion and contraction of the screw machine and the rotation of the door dug by the screw machine or the assembly machine, and vice versa. These interlocking conditions cannot be released under any circumstances, but some equipment can be independently controlled by releasing the interlocking under abnormal conditions. For example, if the cutter head is stopped by releasing the interlocking device, the operation of the belt conveyor or the screw machine can be controlled independently.
Operation of shield machine
Through buttons and knobs, you can operate the operation and stop of cutter head, screw machine and belt conveyor, the selection of cutter head speed, the selection and expansion of propulsion jack, and the opening and closing of screw machine gate. And many other operations are done on the touch screen.
There are two touch screens arranged up and down on the console. Including: operation display, detection display, pump start-up, propulsion, auxiliary operation, other settings, abnormal display and so on. Usually, the upper touch screen can only operate part of the display screen, and the lower touch screen can only operate part of the operation screen. When the touch screen fails, you can switch the failed screen to the normal screen, and you can operate all the screens.
① "Operation display" screen: it mainly displays the status of various equipment, such as the operation status of cutterhead motor, propulsion pump, screw machine, belt conveyor, tail grease pump and assembly translation pump; Open/close state of back door, front door and pedestrian door, extension/contraction of screw jack, confirmation of propulsion conditions, abnormal state, etc.
② "Inspection Display" screen: it mainly displays equipment and construction data, such as cutter head sealing temperature, shield posture angle, hinge angle, propulsion stroke, thrust center position, four-zone thrust, earth pressure, rear gate opening, cutter head speed and torque, propulsion speed and thrust, screw machine speed and oil pressure, cutter head revolution accumulation, etc.
③ "Pump Start" screen: mainly operate propulsion, screw machine, assembly, start and stop of other pumps, and display the running status.
④ "Propulsion" screen: it mainly operates the selection of propulsion jacks, the increase and decrease of oil pressure in four areas, the synchronous setting of jacks, the switching of propulsion speed, etc. , and display the thrust center position, thrust of four areas, total thrust, jack stroke, propulsion speed, etc. , with other operating instructions.
⑤ "Auxiliary Operation" screen: It mainly operates articulated system and shield tail grease system equipment, and displays the running status of these equipment.
⑥ "Other Settings" screen: It consists of several sub-screens, which can set the parameters of the system and earth pressure. The control room also has two touch screens, one for operating mud adding equipment and the other for operating grouting equipment.
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