Digitial Inspection of Retaining Structures on Large Scale

Tunnels, bridges and retaining walls are the backbone of Austria’s infrastructure in the Alpine area. While increased traffic loads, extreme weather events stress the aging infrastructure, their safe operation is of great social-economic importance.  An early detection of structural deficiencies is crucial to minimize costs for rehabilitation measures and to guarantee public safety.

Due to the large number of more than 100 000 retaining structures along public road and railways, the maintenance poses a great challenge to structural operators: communities, counties, the highway agency (ASFiNAG) and federal railways (ÖBB). Ever since the tragic failure of a cantilever wall on the Brenner highway in 2012, novel, objective methods for safety assessment are in high demand. Up to date, traditional surveying methods constitute the state-of-the art in monitoring structural performance of retaining walls in an objective way. However, this method is time costly and requires closure of driving lanes. Therefore, it is unfeasible to monitor a large number of structures with the current state of the art methodology.

The IGMS provides a service for tilt monitoring of retaining walls with mobile mapping. We cooperate with other industry partners to perform data acquisition while travelling with up to 100 km/h. In such way, we can guarantee route availability and do not constrain the free-flowing traffic. Along with data acquisition, we process the big data in a highly automatic manner, so that costs reduce to a minimum when a large number of objects are monitored in one go.

Operators receive a digital representation of the structure, including geo-referenced point clouds with tenths of millions points (click here to access a dataset in a 3D viewer) and images for inspection tasks. More importantly, the processed point cloud data indicates whether deformations or tilt changes occurred between the times of measurements. Lateral displacements larger than 3.5 mm can be identified with 95% confidence. The IGMS method contributes to a fast preselection of malfunctioning structures. In a second step, operators can then initiate more detailed inspection and investigations.

Mobile Mapping is used for map generation and infrastructure inventory primarily. The IGMS approach is unique and there are no comparable studies in terms of deformation analysis with mobile mapping data. However, large scale inspection tasks will have a significant impact in the future, as onerous environmental influences will affect pavement, tunnels, bridges and retaining walls all around the world. Currently, the IGMS service is in operation in Styria and Lower Austria, monitoring 13 retaining walls of different types, shapes and ages. The acceptance of the IGMS service is growing and has the potential to become appied across Austria and beyond its borders.

The IGMS approach relies on efficient data acquisition along with automatic processing to derive deformations and structural changes
Animation of acquiring scan and image data of a crib wall with a commerical mobile mapping system
Laser intensity colored point cloud (click to view in 3D viewer)
Lateral displacement of individual anchored elements of a retaining wall between 06/2017 and 02/2018 (positive values indicate movements towards road)
Further information
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For more details on the methodology and the IGMS service, please contact Slaven Kalenjuk.

Partners
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Related publications
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Kalenjuk S, Lienhart W, Rebhan MJ, Marte R (2019) Large-scale monitoring of retaining structures: new approaches on the safety assessment of retaining structures using mobile mapping, Proceedings Volume 10970, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2019; 109700T (2019): doi

Lienhart W., Kalenjuk S. (2017): Combined Laser Scanning and Image Based Monitoring of Large Infrastructure Objects. IWSHM 2017, September 12th-14th, 2017, Stanford, California, USA: 3147-3154. Reprint

Lienhart W., Kalenjuk S., Ehrhart C. (2017): Efficient and Large Scale Monitoring of Retaining Walls along Highways using a Mobile Mapping System. Proc. 8th Int. Conf. on Structural Health Monitoring of Intelligent Infrastructure – SHMII-8, Brisbane, Australia: RS3-11, 8 p. PDF

Kalenjuk S., Lienhart W., Rebhan M., Marte R. (2018) Neue Ansätze zur Zustandsbewertung bestehender Stützbauwerke basierend auf 3D-Modellen aus dynamischem Laserscanning, Proc. Messen in der Geotechnik 2018. Stahlmann, J. (Hrsg.). Braunschweig: Institut für Grundbau und Bodenmechanik, TU Braunschweig, Band 104: S. 15 - 36 Reprint