TLS

Terrestrial Laser Scanner (TLS)

For several years, the Georisk team has been monitoring limestone cliffs with discontinuous terrestrial laser scanning (TLS), whose stability is controlled by the strength of the rock and the presence of discontinuities. The strength of limestones and dolomites allows them to form stable vertical slopes hundreds of metres high. 

The advantage of TLS monitoring in rock mass characterisation and monitoring is the high spatial resolution, wide coverage, millimetre accuracy and easy data acquisition. Although measurement accuracy can be reduced due to low reflectivity of the observed material (e.g. wet areas), very rough surfaces, bad weather conditions (rain, fog, very high temperature), occlusion zones and areas oblique to the field of view of the TLS.

The objectives of these follow-up campaigns are the following:

• Detection of rockfalls and estimation of volumes. These volumes allow to confirm the Magnitude-Frequency (M-F) relationship of the rockfalls.
• Estimate the volume of potentially unstable masses, in order to identify and locate the potential source areas or PPSD, and a relative evaluation of their degree of stability.
• Quantitatively assess the risk (QRA), in order to estimate the consequences (damage) for people in the different scenarios depending on a possible rupture. To carry out this QRA, a complete record of rockfalls in a long period of time is needed, which allows to know the frequency of these events.

Examples of two block falls detected between two consecutive campaigns.  In purple colour missing volume (top), photographs of the wall (bottom).

.