One of BMT WBM’s specialisations is the engineering and development required to both design, install and assess long-term stress monitoring systems for railway lines.
These systems have been primarily used to maintain rail safety whilst underground long wall mining subsidence is occurring. The system continuously monitors the rail tension and temperature as well as other sensors specific to a particular site, and remotely provides web-based information to clients and their representatives. The system can also issue alarms when predetermined thresholds are reached and urgent attention is required.
Similar systems have been installed at other locations for a variety of different tasks. These have included estimating the weight of rolling stock passing over a bridge, measuring stress in natural gas and ammonia pipes during mine subsidence and monitoring bridge movements.
BMT WBM has full third party Quality Assurance accreditation to AS/NZS ISO 9001:2000. The QA system utilised by BMT WBM includes specific procedures for design, design review, project management, site troubleshooting, post-processing, analysis and reporting.
Long-Term Rail Monitoring Capability
BMT WBM have developed and installed a monitoring system to maintain rail safety during long wall coal mining beneath the main southern rail line, south of Sydney, The initial monitoring system was installed in 2006 to allow mining near the rail corridor, whilst the current system which is still in use allowed the mine to pass under the tracks.
The major issue with mining underneath the corridor is that the subsidence related ground shear affects the Continuously Welded Rail (CWR) pre-stress or Stress Free Temperature (SFT). To allow for these ground movements a number of expansion switches has been installed in the rails.
The monitoring system consists of a series of strain gauges and temperature sensors located over a 1 km long section of track, and displacement transducers mounted to each switch blade. These sensors are recorded at five minute intervals and analysed on site by a series of data loggers. When a reading exceeds one of the predefined triggers an alarm is sent out via an SMS.
Due to the critical nature of the system it is designed around reliability and fail-safe architecture to ensure all alarms are received by the necessary personnel. The monitoring system is modular in design to minimise the effect of a component failure and to allow the system to be easily repositioned as the subsequent long wall panel’s progress.
Rail strain / stress is monitored via strain gauges bonded to each rail and wired to measure pure axial tension or compression. Impact on the rail is negligible with two small holes drilled for cabling requirements and a third if there is a temperature sensor at the location. The resistance between the strain gauges and the rail is checked during installation to ensure they will not interfere with the track signalling. The installation can be performed during normal train running, under TWA protection. The gauges are protected from the environment with a multilayer coating to maximise their service life.
Displacement transducers are used to measure the daily expansion of the rails with temperature as well as the subsidence related movements. During active subsidence the trends for both the displacement sensors and strain gauges give an early warning, prior to the system hitting an alarm level. This allows any maintenance to be planned in advance to ensure there is no impact on rail traffic.
The system consists of a number of cabinets located along the rail corridor with each cabinet monitoring its own section of track. The cabinets are linked via an Ethernet network to a SCADA system to show the system status and alarms to the onsite track certifier and the mines control room. BMT WBM personnel can log in and remotely manage the system.
The current system is located in the centre of Tahmoor and is mains powered via a 24V battery system with 3 days reserve power. Communications to and from the site are via a combination of ADSL and mobile internet. For remote areas solar power and mobile or satellite internet would be used based on the availability of services.
Data from the monitoring system is automatically uploaded to the BMT WBM Monitoring website every 15 minutes and in the event of an alarm. The website gives the user the ability to choose the sensors and time frame they wish to plot. This allows everybody associated with the project access to the latest data for decision making or analysis purposes. Data can also be downloaded for further detailed analysis.
BMT WBM Structural Health Monitoring Projects
- Booragul rail subsidence monitoring (current BMT WBM staff)
- Tahmoor Rail Subsidence Monitoring
- Inghams ammonia pipe work subsidence monitoring
- Myrtle Creek culvert subsidence monitoring
- Mallaty Creek natural gas pipeline subsidence monitoring
- Unnamed Creek natural gas pipeline subsidence monitoring
- Rocky Ponds natural gas pipeline subsidence monitoring
- Appin 2A natural gas pipeline subsidence monitoring
- Port Kembla L-Bridge rolling stock weight monitoring, structural strain gauging
For general enquiries relating to Rail Monitoring, please contact Neil Watson
Business Unit Manager, Sydney Machinery Group