How to do automated monitoring of subway operations in China-taking Shenzhen subway as an example

 

Shenzhen Metro currently has 8 operating lines with a total length of about 304.3 kilometers. The average daily passenger flow exceeded 6.62 million last year, accounting for 60% of the total bus trips. Of course, due to the recent epidemic, the daily passenger flow is only about 2.5 million, less than half of the usual. There are currently 17 subway lines under construction in Shenzhen, with a total mileage of 321.88 kilometers, of which 7 lines will be put into operation this year, about 107 kilometers.

 

The density of Shenzhen’s subway is relatively high in China. Shenzhen only has more than 2,200 square kilometers. 33 lines of 1,335 kilometers of subways will be built before 2035. The density is so high that you can imagine. In order to ensure the safety of subway lines with such a large density, there are three situations that require automated monitoring during the construction and operation periods:

 

  1. When a newly built subway line cross an existing operating subway line, the existing line must be automatically monitored.
  2. When various constructions are carried out within the scope of the existing operating subway security zone, such as excavation of foundation pits, pile foundation construction, construction of road interchanges, etc., the existing lines must be automatically monitored.
  3. The operating subway tunnel has been severely deformed due to external influences. When the tunnel structure needs to be repaired urgently, automatic deformation monitoring of the existing subway tunnel is required. This situation often requires higher monitoring point density and monitoring frequency.

 

  1. Shenzhen subway automated monitoring adopts three relatively mature and highly applied technologies

 

  1. Measuring robotics

The measuring robot adopts a motor-driven and software-controlled TPS (Total station Positioning system) system. It is an intelligent total station combined with laser, communication and CCD technology, integrating automatic target recognition, automatic aiming, automatic angle measurement, and automatic distance measurement , A measurement system integrating automatic target tracking, remote control, and automatic data recording. Commonly known as “measurement robot”, the angle measurement accuracy reaches 0.5″, and the distance measurement accuracy is 0.6mm+1ppm. The measurement robot, reference points, monitoring points, plus data transmission system and background control analysis system, a total of 5 parts constitute the whole The automatic monitoring system of the measuring robot. After the system is set up, it can automatically start to work. It can realize the functions of automatic observation, recording, processing, storage, deformation report preparation and deformation trend display without operator intervention. This monitoring is adopted The technology has the following features: (1) High precision, with a precision of up to 0.5mm. (2) It can be monitored by a single unit or multiple units can be connected to the network. (3) The relative coordinate system can also be used for absolute coordinates. It can monitor the absolute deformation of the tunnel. (4) The degree of automation is high, and it can be monitored throughout the day. (5) The real-time performance is poor, and it takes about half an hour for a single instrument to give the monitoring result at the earliest. (6) Instrument The price is high and the maintenance cost is high.

 

 

  1. 3D laser scanning technology

 

Three-dimensional laser scanning technology is also known as real-world copy technology. It uses the principle of laser ranging to record the three-dimensional coordinates, reflectivity and texture information of a large number of dense points on the surface of the measured object. Combining computer vision and image processing technology, the scan result is directly displayed as a point cloud (pointcloud: the result of countless points presenting objects in the computer according to measurement rules), which can quickly reconstruct the three-dimensional model and line of the measured target. Various drawing data such as face and body. Such comprehensive information can give people a feeling of real reproduction of objects in the computer. Therefore, 3D scanning technology is known as “a technological revolution following GPS technology” in the field of surveying and mapping. As a high-tech in the field of surveying and mapping, 3D laser scanning technology has been widely used in cultural relics protection, urban construction surveying, topographic surveying and mapping, mining, deformation monitoring, pipeline design, aircraft and shipbuilding, highway and railway construction, tunnel engineering, bridge reconstruction and other fields. For the first time, the Shenzhen Municipal Institute applied 3D laser scanning technology to the monitoring of the Shenzhen subway. The application effect is very good. It is under our promotion that the Shenzhen Metro Group has made 3D laser scanning one of the must-do projects for subway safety protection zone monitoring.

 

Three-dimensional laser scanning can play the following five roles in the monitoring of subway tunnels:

 

(1) The tunnel scanning result can record the real state of the tunnel, and display the three-dimensional situation of the tunnel very intuitively. Through the presentation of multiple perspectives, it gives people an immersive feeling. (2) The defect information of the tunnel can be recorded and quantified, such as marking the area of ​​the seepage area or the damaged area, etc.; (3) The point cloud information obtained by scanning the tunnel structure can be compared with the design value of the tunnel. The deviation between the tunnel structure and the design drawings can be obtained by comparing the results of two tunnel scans in different periods, and the deformation of the tunnel structure during this period can also be known; (4) The three-dimensional point cloud diagram can be used to visually display the deformation data of the tunnel monitoring point: using three-dimensional As a data carrier, the point cloud diagram can visually display the deformation data of each monitoring point; (5) The three-dimensional point cloud data can be published in IE browser format, and information can be inquired even if there is no professional software.

Three-dimensional laser scanning technology has the following characteristics:

(1) The scanning speed is fast, the results are intuitive, the information is rich, and the point cloud data is widely used. (2) It is easy to operate, it can be swung to scan or move to scan. (3) The relative coordinate system or the absolute coordinate system can be selected to monitor the absolute deformation of the tunnel. (4) Automatic scanning is not possible, and manual scanning can only be performed after the subway is out of service. (5) The accuracy is slightly lower, generally 3~5mm. (6) The price of the instrument is high.

 

  1. 3. Real-time monitoring technology for tunnel convergence

Shenzhen Municipal Institute has independently developed a set of real-time monitoring system for tunnel convergence in operation (it has obtained 2 utility model patents). This system includes four parts: one is the mainframe of the laser rangefinder, which is used to measure the width of the tunnel section; It is a control and transmission device used to receive remote commands to control the laser rangefinder and automatically send data to a remote data server; the third is a data server, which is used to store and manage data; the four application-side control analysis software is used to send control commands and Data analysis shows. Among them, the laser rangefinder and control and transmission equipment can be integrated, the transmission data adopts mobile 2G/3G/4G signals, and the application-side control analysis software can be installed on a computer or mobile phone. The real-time monitoring data can be accessed and displayed through the mobile phone, and the data can be collected every 5 seconds at most. It is very practical especially during the grouting reinforcement period, and can guide the adjustment of grouting parameters in time.

The characteristics of tunnel convergence real-time monitoring technology: (1) Real-time is very strong, up to 5 seconds to monitor and feedback data. (2) Easy to install and use, it can be controlled and observed on the mobile phone. (3) Automatic monitoring can be carried out around the clock. (4) Cheap price and low maintenance cost. (5) The accuracy is medium, generally 1~2mm, which meets the convergence monitoring requirements. (6) Only the relative coordinate system can be selected to monitor the relative deformation of the tunnel.

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