In tunnelling, a detailed understanding of the ground is essential. This includes geological characterisation to select appropriate excavation methods, management of geotechnical risks such as collapse and groundwater, structural design that adapts to geological conditions, efficient choice of machinery, and minimisation of environmental impacts. A thorough geological analysis beforehand is crucial to ensure the safety and efficiency of the tunnel project.

TBMs are machines with very high excavation performances, but they are still very sensitive to geological uncertainty along the route and to unplanned events such as: faults, caverns, water pockets, boulders, foundations, etc. This geological uncertainty is the biggest cost overrun in a TBM construction project. Therefore, it is of great importance to know the geological conditions ahead of the excavation face to avoid performance losses or critical failures in the TBM, as this knowledge will allow to automatically adjust the operating parameters or to execute the most appropriate treatments for ground conditioning.

ACCIONA is launching this challenge to identify a geological reconnaissance or exploration system, both at the level of sensorisation and at the level of interpretation and visualisation software that will enable a geological characterisation of the terrain to be carried out. This system must provide new geological reconnaissance techniques for tunnel boring machines ahead of the excavation face, both from the surface and from the machine itself. The requirements for the solution are:

• Non-intrusive solution to the environment
• Does not affect machine productivity
• Enable consistent and coherent identification of profound changes in terrain characteristics.