Leica Geosystems TruStory Monitoring System at West Station, MTR

Scope/Objective Tunnel deformation monitoring

Customer/Institution MTR, Hongkong

Date 2009 - ongoing

Location Hongkong

The TW7 area in System design and setup Station , is the planned The design of the tunnel monitoring location for the development of system started in 2009 and required Project Summary a new urban infrastructure. Since two months to complete the design, Used Instruments the construction is very close to preparation, setup and testing. In Leica TM30 an existing MTR (Mass Transit total, six high accurate Leica TM30 Leica Geosystems L-bar prisms Railway, the railway total stations, two computers, one Software system in Hong Kong) tunnel and backup computer, 42 reference Leica GeoMoS Monitor / Analyzer station, an automatic deformation prisms and 234 monitoring prisms Web Service for data viewing monitoring system (ADMS) must have been installed for the monitoring of the SU Hongkong be installed for security, because system. The locations of the total Third party adjustment software Communication any deformation to the MTR could stations and prisms were carefully Cables threaten the lives of thousands selected so that measurement cov- of passengers. erage, efficiency and the costs of Challenge the project were balanced. The total - Monitor a length of 400 meters A Netherlands company has been stations were distributed along a - Ensure the required clearance contracted to monitor the develoment 400 meter segment of the railway between installation and railway of this project for any deformation tunnel. The total stations we infrastructure that may occur due to earth and piling installed in three groups of two, - Fully automated and reliable system works. To perform the deformation with one total station of each pair to very limited access to the site monitoring Leica Monitoring solutions was set to monitor the uptrack, the has been selected. This is because other the downtrack (see Figure 4). the realtime monitoring is able to The monitoring prisms were continuously detect any deformation, installed next to overhead line therefore providing an alert to any cables, on the sides of the tunnel possible disasters. and next to the pedestrian walkway. Benefits - Ensure the safety for the daily railway operation - React proactive on any occurring deformation to avoid downtimes of the railway tunnel / station

For each prism a clear line of sight outside the monitoring area and addition, the end customers have to the total stations and safety partly inside the monitoring area. As the ability to access via a web inter- clearance to the tracks and over- not every total station had a line of face the measured monitoring data head lines was required. sight to the outside stable reference that represents the deformations in points, it was necessary to compute easily understandable graphical and Communication network adjustments for the complete numerical deformation reports. was established between the total network based on the outside stable stations and the dedicated monitoring reference points, so that the inside Messaging System computers using cables. These com- reference points could be updated. To enable quick response to any puters were located in a separate For that reason, at the beginning of irregularities in the project area, a office with a workstation equipped each complete monitoring cycle, the messaging system was implemented. with Leica GeoMoS Software. This total stations measure all the reference This system automatically informs is responsible for the Leica TM30 points. These measurements are used the responsible staff via e-mails in cotrol, data collection, analysis and to compute the network adjustment. any situation when a measured visualization. In addition, third party The coordinates of the total station displacement exceeds set limit levels. network adjustment software was standpoints and the reference points These limit level values have been used. Reliability to the system was inside the monitoring area are set through the system beforehand ensured by using uninterrupted updated with the results. Leica by the surveyors. After a limit level power supplies (UPS), to reduce the GeoMoS software then measures is exceeded, the surveyors in charge problems of power outages, and the monitoring points based on the investigate the reasons behind the data was frequently backed up. updated reference points. This exceedance and confirm whether Regular maintenance and checks complete measurement cycle, with the measurement was due to outliers, including cleaning the optical prisms stable reference and monitoring human errors, construction activities twice a week, allowed the system to points, occurs every 2 hours. or a real movement. operate smoothly and accurately as the trains, running frequently next Deformation Data Conclusion to the instruments, could cause The monitoring data is available in In the last decade, it has been proven unwanted displacements and dust real-time for displaying through the that the automatic deformation coverage of the prisms. Internet. The monitoring staff, with monitoring systems have effectively appropriate access codes, can login prevented accidents from happening Monitoring Network to the complete monitoring system since its implementation in various The stable reference prisms were information and display both deformation projects in Hong Kong. installed along the tunnel, partly values and the system health. In

Leica Geosystems AG Heinrich-Wild-Strasse CH-9435 Heerbrugg Switzerland Phone +41 71 727 31 31 www.leica-geosystems.com