Infrastructure: Deformation Monitoring with TLS

Mining infrastructure has the ability to move over time due to inherent instability in the ground surface caused by seasonal weather variations and post construction settlement. The trouble is some monitoring techniques have deficiencies!

Traditionally the relative movement of structures has been monitored using conventional survey techniques involving the repeat measurements to prisms or targets mounted on the structure from known survey control stations. The subsequent measurements are compared to determine the relative movement over time of the structure. This type of monitoring only provides the surveyor and structural engineer with the localised movement of the structure in the vicinity of the measurement point on the structure and cannot accurately determine the total movement of the structure.

AAM has an advanced technique for monitoring structures using Terrestrial Laser Scanners (TLS) to accurately monitor the relative movement of the whole structure over time. A TLS allows millions of individual measurements to be observed across the surface of the structure instead of the isolated points observed using traditional methods.

As the TLS scan location is referenced to the existing site survey control, subsequent scans of the structure can be compared to either a common reference plane or each another. This method of comparison involves the TLS point cloud surface being ‘cleaned’ of erroneous data and compared to a vertical plane. Through the use of vertical plane offset colour mapping the surveyor and structural engineer are able to accurately monitor the relative movement of the whole structure over time and determine localised areas of distortion (as depicted in the images below).

Should the level of movement be deemed to be of concern, the monitoring interval can be increased to allow the relative movement over time to be determined and the appropriate structure failure measures to be put into place.

Case Study
The images below depict the monitoring process undertaken on a ROM RE Wall. The images show an intensity based laser scan image through to final deliverable in the form of an intensity based plot.

Above: Registered point cloud of a ROM Hopper and RE Wall



Above: This image indicates the amount of deformation to a vertical plane of the cleaned TLS point cloud surface to the vertical plane. The colour variation indicates the amount of deflection from the vertical plane, from minimal movement (yellow) through to maximum movement (red). The graduation in deflection is shown in the legend on the left of the point cloud.

For more information on TLS, click here.