Deformation monitoring

Deformation monitoring (also referred to as deformation survey) is the systematic measurement and tracking of the alteration in the shape or dimensions of an object as a result of stresses induced by applied loads. Deformation monitoring is a major component of logging measured values that may be used to for further computation, deformation analysis, predictive maintenance and alarming.[1]

A radio telemetry wireline extensometer monitoring slope deformation.

Deformation monitoring is primarily related to the field of applied surveying, but may be also related to civil engineering, mechanical engineering, construction, and geology. The measuring devices used for deformation monitoring depend on the application, the chosen method, and the preferred measurement interval.

Measuring devices
A standard geodetic monitoring instrument in the Freeport open pit mine, Indonesia
GNSS reference station antenna for structural monitoring of the Jiangying Bridge

Measuring devices (or sensors) can be sorted in two main groups, geodetic and geotechnical sensors. Both measuring devices can be seamlessly combined in modern deformation monitoring.

Application

Deformation monitoring can be required for the following applications:

  • Dams[5]
  • Roads
  • Tunnels
  • Bridges and Viaducts
  • High-rise and historical buildings[6]
  • Foundations
  • Construction sites
  • Mining[7]
  • Landslide areas[8]
  • Volcanoes
  • Settlement areas
  • Earthquake areas

Methods

Deformation monitoring can be manual or automatic. Manual deformation monitoring is the operation of sensors or instruments by hand or manual downloading of collected data from deformation monitoring instruments. Automatic deformation monitoring operation of a group of software and hardware elements for deformation monitoring that, once set up, does not require human input to function.

Note that deformation analysis and interpretation of the data collected by the monitoring system is not included in this definition.

Automated deformation monitoring requires instruments to communicate with a base station. Communication methods used include:

Regularity and scheduling

The monitoring regularity and time interval of the measurements must be considered depending on the application and object to be monitored. Objects can undergo both rapid, high frequency movement and slow, gradual movement. For example, a bridge might oscillates with a period of a few seconds due to the influence of traffic and wind and also be shifting gradually due to tectonic changes.

  • Regularity: ranges from a days, weeks or years for manual monitoring and continuous for automatic monitoring systems.
  • Measurement interval: ranges from fractions of a second to hours.

Deformation analysis

Deformation analysis is concerned with determining if a measured displacement is significant enough to warrant a response. Deformation data must be checked for statistical significance, and then checked against specified limits, and reviewed to see if movements below specified limits imply potential risks.

The software acquires data from sensors, computes meaningful values from the measurements, records results, and can notify responsible persons should threshold value be exceeded. However, a human operator must make considered decisions on the appropriate response to the movement, e.g. independent verification though on-site inspections, re-active controls such as structural repairs and emergency responses such as shut down processes, containment processes and site evacuation.

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See also

References
  1. Literature, Edited by J.F.A Moore (1992). Monitoring Building Structures. Blackie and Son Ltd. ISBN 0-216-93141-X, USA and Canada ISBN 0-442-31333-0
  2. Dai, Keren; Li, Zhenhong; Tomás, Roberto; Liu, Guoxiang; Yu, Bing; Wang, Xiaowen; Cheng, Haiqin; Chen, Jiajun; Stockamp, Julia (December 2016). "Monitoring activity at the Daguangbao mega-landslide (China) using Sentinel-1 TOPS time series interferometry". Remote Sensing of Environment. 186: 501–513. doi:10.1016/j.rse.2016.09.009. ISSN 0034-4257.
  3. Pardo, Juan Manuel; Lozano, Antonio; Herrera, Gerardo; Mulas, Joaquín; Rodríguez, Ángel (2013-09-15). "Instrumental monitoring of the subsidence due to groundwater withdrawal in the city of Murcia (Spain)". Environmental Earth Sciences. 70 (5): 1957–1963. doi:10.1007/s12665-013-2710-7. ISSN 1866-6280.
  4. Díaz, E.; Robles, P.; Tomás, R. (October 2018). "Multitechnical approach for damage assessment and reinforcement of buildings located on subsiding areas: Study case of a 7-story RC building in Murcia (SE Spain)". Engineering Structures. 173: 744–757. doi:10.1016/j.engstruct.2018.07.031. ISSN 0141-0296.
  5. Tomás, R.; Cano, M.; García-Barba, J.; Vicente, F.; Herrera, G.; Lopez-Sanchez, J.M.; Mallorquí, J.J. (May 2013). "Monitoring an earthfill dam using differential SAR interferometry: La Pedrera dam, Alicante, Spain". Engineering Geology. 157: 21–32. doi:10.1016/j.enggeo.2013.01.022. ISSN 0013-7952.
  6. Tomás, Roberto; García-Barba, Javier; Cano, Miguel; Sanabria, Margarita P; Ivorra, Salvador; Duro, Javier; Herrera, Gerardo (November 2012). "Subsidence damage assessment of a Gothic church using differential interferometry and field data". Structural Health Monitoring. 11 (6): 751–762. doi:10.1177/1475921712451953. hdl:10045/55037. ISSN 1475-9217.
  7. Herrera, G.; Álvarez Fernández, M.I.; Tomás, R.; González-Nicieza, C.; López-Sánchez, J.M.; Álvarez Vigil, A.E. (September 2012). "Forensic analysis of buildings affected by mining subsidence based on Differential Interferometry (Part III)". Engineering Failure Analysis. 24: 67–76. doi:10.1016/j.engfailanal.2012.03.003. ISSN 1350-6307.
  8. Dai, Keren; Li, Zhenhong; Tomás, Roberto; Liu, Guoxiang; Yu, Bing; Wang, Xiaowen; Cheng, Haiqin; Chen, Jiajun; Stockamp, Julia (December 2016). "Monitoring activity at the Daguangbao mega-landslide (China) using Sentinel-1 TOPS time series interferometry". Remote Sensing of Environment. 186: 501–513. doi:10.1016/j.rse.2016.09.009. ISSN 0034-4257.
  • Literature, B. Glisic and D. Inaudi (2008). Fibre Optic Methods for Structural Health Monitoring. Wiley. ISBN 978-0-470-06142-8
  • Literature, John Dunnicliff (1988,1993). Geotechnical Instrumentation For Monitoring Field Performance. Wiley. ISBN 0-471-00546-0

Further reading
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