Geotechnical Modelling of the Riyadh Metro Line 3 Using Multi-technique Geophysical Survey

The Riyadh Metro Project is currently the largest public rail infrastructure project in the world under implementation. Metro will become the backbone of the city's public transport, significantly improving the life quality of citizens. We helped to carry out an exhaustive geophysical survey along the entire corridor of the Riyadh’s Metro Line 3. Among all the six Lines that the System comprises, Line 3 is the longest. It runs along 42 km, of which we identified about 13 km long underground sections (TBM EPBS and cut and cover) and 11 underground stations (cut and cover). The geophysical survey comprised a variety of field tests: seismic refraction, electrical resistivity tomography, ground penetration radar and seismic tests in boreholes (downhole and cross-hole testing). We correlated the results of the geophysical surveys with data coming from geological, hydrogeological and geotechnical investigations. This way, we delivered a continuous subsurface profile, which became the raw data for developing a full detailed geotechnical and hydrological model for the Line 3. The said model anticipated potential geotechnical risks (layers owning poor engineering parameters, karstic areas, faults or weaker rock volumes within the rock mass). Then, mitigations helped achieving, reliable, durable, safe and efficient designs and construction works.