Contributions to Proceedings:

R. Wenighofer, R. Galler, W. Karel, N. Pfeifer:
"Efficient Digital Imaging for Full Face Rock Mass Evaluation in Hard Rock TBM Tunnelling";
in: "ISRM International Symposium - EUROCK 2020", 69; issued by: International Society for Rock Mechanics and Rock Engineering; OnePetro, 2020, ISBN: 978-82-8208-072-9, 1 - 7.

English abstract:
TBM tunnelling comprises a wide range of advance rates depending on the rock conditions. Thus, a common consent on TBM performance between client and contractor is necessary which is substantiated by an unambiguous digital basis to propound an objective documentation of the rock mass. In TBM tunnelling, subjective and different characterisation of the face by manual recordings of geologists of client or contractor is common since the cutter head has only few openings and obstructs the geologist's view of the face.

Research activities in TBM tunnelling have addressed these deficiencies for years and have designed systems mainly focusing on imaging techniques. However, limited fields of view, the need to support the face using the cutter head and to retract the cutter head by a large distance hinder their application. Especially in weakness or failure zones, cutter head retraction is reduced significantly.

The contribution presents an imaging system used in a cutter head of a hard rock TBM which overcomes the restrictions mentioned. To accelerate image recording, various cameras mounted in different disc housings simultaneously image the tunnel face when rotating the cutter head in excavation pauses, and provide a digital representation of the face. The image data is processed in a photogrammetric tool chain and employs latest structure from motion techniques and a variant of the iterative closest point algorithm. This ensures an efficient system application as well as a metric digital full-face 3D-reconstruction, concerning both geometry and appearance, to impede ambiguous rock mass characterization.

The contribution further refers to the practical utilization of the imaging system during 20 months on the hard rock TBM in the exploration tunnel of the project Brenner-Base-Tunnel and reveals the advantages of advanced processing techniques for its efficient and rapid utilization in this harsh environment.

Photogrammetry, TBM, Imaging System, Rock mass characterization

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