The problems caused by sinkhole subsidence in the transport network constitute a geological risk that is rapidly increasing in different regions of the world. The Digital Cartography and 3D Analysis Laboratory at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) has participated in a study that has just been published in the journal Earth Surface Processes and Landforms, on monitoring the sinkhole subsidence processes affecting the conventional railway network in Aragón (Spain).

Detecting and quantifying this subsidence is fundamental to designing and applying effective mitigation measures to avert accidents in transport networks. Specifically, this study has centered on monitoring the subsidence processes in sinkholes produced by the dissolution of gypsums and salts, that are affecting the transport infrastructures near the city of Zaragoza.

“To conduct this monitoring, we have combined geomorphological cartography, geophysical survey techniques such as ground penetrating radar, high-precision leveling and high-resolution terrestrial laser scanning”, says the geologist Alfonso Benito Calvo, who is responsible for the Digital Cartography and 3D Analysis Laboratory.

3D scanning

To discover how the ground is moving in three dimensions, scans were carried out every six months, and these were analyzed with a new methodology that correlates and compares the ground geometry but without the need to install physical control points. This methodology simplifies the logistics of monitoring and expands the number of contexts where it could potentially be applied, including inaccessible locations.

“The results establish the spatial-temporal pattern of the sinkholes, detecting the zones affected by subsidence and how fast this is happening, with average values of 6 mm/year calculated, and extreme values of 26 mm/year”, explains Benito Calvo.

Collaboration with the UNIZAR

This study is part of the collaborative work between the Universidad de Zaragoza (UNIZAR) and the scientific-technical services provided by the CENIEH as a Unique Scientific and Technical Infrastructure (ICTS), which has been under way since 2014 and has already borne fruit in several scientific works for international conferences and journals, on geomorphology, teledetection and geological engineering.

It is financed by the CGL2017-85045-P project from the Ministerio de Ciencia, Innovación y Universidades, led by the Universidad de Zaragoza, and is part of the work for a doctoral thesis co-financed by the Spanish Government and the European Social Fund (predoctoral contract PRE2018-084240), co-supervised by the Universidad de Zaragoza and the CENIEH.