Trustory UK Hongkong Tai Wai Depot.Indd
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Leica Geosystems TruStory Monitoring Rail Tracks during Construction of Noise Barriers/HK Objective Deformation monitoring due construction works close to existing railway tracks Customer/Institution MTR (Mass Transit Railway, Hong Kong) Date 2009 – ongoing Location As one of the busiest and most have been built along the tracks Project Summary crowded rapid transit system in the since 2009. However, before any Instruments world, MTR (Mass Transit Railway, works started, safety had to be Leica TCA2003 Total Station Hong Kong) operates high frequency ensured. Since the barriers were Leica Geosystems Monitoring prisms train services from early morning built very close to the existing Software until midnight. Due to the noise tracks, deformation due to digging Leica GeoMoS Monitor / Analyzer of the trains, areas where trains and various works for the con- Web viewer for displaying data and reports operate outdoors, like Tai Wai, struction of the barriers might Communication suffer significantly from noise have seriously affected the position Cables pollution. Serving as the busest of the tracks and subsequently Uninterrupted Power Supley (UPS) interchange station in New Territories, train operation. Therefore, an connecting Ma On Shan Line to automatic deformation monitoring Challenge East Rail Line, Tai Wai Station and system was implemented so that - Real-time deformation monitoring Depot are also one of the busiest relevant preventive actions could throughout the construction hubs for train operation. As resdents be performed if an unpredicted - Maintenance of the prisms and total move into the newly built residential deformation was detected by the stations in restricted MTR zones buildings above Tai Wai Depot, real time monitoring system. the noise pollution problem is Benefits expected to affect an increased Monitoring System Setup - Continuous and remote monitoring - The safety of millions of MTR number of people. The monitoring systems consists passengers can be ensured round of six total stations TCA2003, two the clock In order to alleviate the noise computers, 23 reference prisms pollution problem, noise barriers and over hundreds of monitoring monitoring measurements were taken continuously in automatic two-hour cycles using the Leica GeoMoS software. All monitoring results were uploaded to the Internet for instant browsing and were closely monitored by surveyors. Any deviated data would immediately be investigated by surveyors to check the accuracy. Messaging System One of the main purposes of setting up an automatic deformation monitoring system was to inform the responsible staff of a situation when irregularities occurred in the construction site. After the monitoring Control Center of the Monitoring System positions of the optical prisms are prisms. The total stations were and power cables respectively. measured, they are compared with sub-divided into two groups and The two computers were located the set limit levels. If any monitoring located in Zone 1 and 2 of the in a workstation equipped with data reached or exceeded one of construction site. Each location Leica GeoMoS software which is the three limit levels, the messaging for the total stations was selected responsible for the control of the system would immediately be under various conditions, including sensors, collection and analysis activated. The designated personnel solid foundations, safe distance of data and the. In addition, both of MTR and the Contractor would from tracks and high-voltage computers were connected to a be notified by e-mail. The surveyors overhead lines, and a clear sight web server via broadband internet, in charge would then investigate to every monitoring and reference so that users can access the the reasons behind the notification prism. sys-tem remotely. and confirm whether the message The monitoring prisms were installed was due to faulty equipment, human at the upper and lower levels of Leica TCA2003 Total Station can error or construction activities. overhead line masts to check achieve an accuracy of ± 0.5” Additional respective measures tilting and also on the railway in angle and 1 mm ± 1 ppm in may be taken according to the sleepers. The reference prisms distance. To achieve good visibility severity of the message, ranging were distributed around the total for the total stations, clean and from increasing the monitoring stations so that each total station not fogged prims in the correct frequency to immediate cessation could measure to approximately position with a constant light con- of all foundation and excavation six prisms and compute the dition with a dark background and works. stability and orientation of the no atmospheric disturbance were total stations. needed. Reporting An uninterrupted power supply All monitoring data was displayed (UPS) was provided to each total Data Acquisition in graphs showing and every 24 station to ensure the system could The operation of the automatic hours a report was generated. overcome any temporary power deformation monitoring systems shortage. started two weeks before the Maintaining Stability construction works commenced as Notwithstanding the high precision The total stations were connected so-called reference or null epoch of the surveying instruments and to two computers and the UPS in data had to be collected. Throughout careful planning, every component the workstation via signal cables the construction, the deformation in the system must perform sturdily to provide reliable data. the instruments be examined for display the monitoring results to However, maintaining the stability damage or defects on regular the customer. of such a complex system is never basis, but surveyors also assessed an easy task. First and foremost, the system for any possible future High Precision: As surveying has maintenance of the equipment damage caused by other construc- always been renowned for its high was carried out annually and wear tion activities or improvement accuracy, surveyors strived to outs and damages were fixed works carried out by MTRC. produce measurements as accurate during this maintenance period. as possible. However, human Since most of the instruments Advantages measurements can never be as were installed along the tracks Continuous Measurements: The accurate as those of machines, and masts, which belong to the most important reason of imple- especially in a dark environment. restricted zone, working group menting an automated system was To provide a highly precise moni- meetings with MTRC were arranged its non-stop measurements taking. tor-ing system, the automatic to discuss the permitted working In the past, when measurements deformation monitoring system hours and site possession. Other were taken by manual survey, data minimizes the use of human than hardware maintenance, collected could be fragmented as labour with the replacement of calibration of instruments was it was impossible for surveyors to newly developed total stations, another important element to work all day resulting in incomplete which ensures extremely reliable maintain stability. The system was analysis and the process was not measurements. tested prior to installation of the cost-effective. With the automatic instruments to ensure that they deformation monitoring system, Conclusion were working and configured comprehensive reports could be The success of the monitoring properly. From time to time, generated solely by computers system has shown that safety can during the course of monitoring, and an efficient messaging system be ensured with the help of ad- the positions of the back sight enables deformation to be vanced technology, especially for prisms on the total station masts detected at all times. works carried out in a train system and the selected monitoring target which carries millions of passengers prisms were checked by manual Remote Monitoring: A considerably every day. Such a flexible yet survey to verify that the automatic short period of time available for efficient system has demonstrated measurements had been made track possession was another that safety can be maintained correctly, as the prisms might have significant constraint for works round the clock and does not been displaced either acciden- in an operational railway system. necessarily come with interference tally or naturally. The automatic With surveyors monitoring the to our daily lives. measurements could be corrected system anywhere via the Internet, using data from manual system the system could be operated checks when necessary. At the without interfering with train same time, all optical prisms were services. Surveyors and other staff regularly cleaned and checked did not have to travel to the site for stability, orientation and firm to check for any irregularities and attachments. In cases of obstruction reports could be seen in just a few to the sight line of the total stations, clicks. prisms were relocated to other stable locations. They would also User-Friendliness: To increase the be re-installed if they were found efficiency of the system, a user- loose. Moreover, not only would friendly web interface was used to Leica Geosystems AG Heinrich-Wild-Strasse CH-9435 Heerbrugg Switzerland Phone +41 71 727 31 31 www.leica-geosystems.com.