Tunnel boring machines (TBMs) are increasingly being utilized in major projects such as the Brenner Base Tunnel in the Austrian Alps. However, geological documentation of the drilling face has traditionally lagged behind that of conventional tunnel drives, primarily due to visibility restrictions. In collaboration with Geodata GmbH, the Institute for Subsurface Engineering at Montanuniversität Leoben in Austria has developed a camera system for TBMs used in tunnel construction projects. This innovative solution addresses the challenges associated with restricted visibility and enables high-resolution geological documentation.

The Challenge of Restricted Visibility

In conventional tunneling, geological mapping is typically performed by a geologist without significant obstructions to the view of the face. However, in mechanized tunneling, the cutter head obstructs the view, leaving only limited openings such as scrapers, cutting discs, and manholes for observation. This restriction severely limits the accuracy and comprehensiveness of geological mapping.

A Camera-Based Solution

The Institute for Subsurface Engineering has developed a rugged camera system designed to be mounted in disc housings within TBMs. This system provides high-resolution images and color-coded relief presentations of the entire drilling face, enabling detailed analysis of mineral composition, stratification positions, and cavity depths. The valuable data obtained from this system allows engineers to assess structural stability, verify the accuracy of geological models, and ensure continuous tunnel boring operations without disruption.

The camera-based system is designed to be lightweight and flexible, allowing it to be mounted in different disc housings without requiring additional openings. The number of camera tracks can be adjusted based on the distance between the retracted cutter head and the face, making it adaptable to various TBM configurations. Installation options include a single camera or multiple cameras for enhanced coverage.

The control unit, housed within the disc near the rotation center of the cutter head, includes a PC, power supply, and an uniaxial inclination sensor. It also provides interfaces for parallel operation with multiple cameras, significantly accelerating data acquisition during measuring campaigns. The camera control software is based on Allied Vision’s Vimba SDK, which triggers cameras at a fixed rate of two images per second to ensure sufficient overlap and image surplus.

High-Resolution Imaging for Photogrammetry

The camera system delivers high-resolution images ideal for photogrammetric analysis. This technique uses digital images to create 3D models by employing various measuring and evaluation methods. The result is a detailed, dense 3D reconstruction of the entire drilling face. Additionally, the system generates orthophotos—distortion-free, true-to-scale representations of the surface—with uniform illumination covering both break-outs and stable areas. These orthophotos reveal details that cannot be observed directly behind the cutter head.

Based on these images, a color-coded relief presentation of the face is generated, providing visual insights into geological features. Robert Wenighofer, Project Assistant at the Institute for Subsurface Engineering, emphasizes: “Digital imaging of the face leads to objective geological mapping, which offers an incontrovertible basis for geological assessment.”

Durability and Advanced Features

The rugged Prosilica GT2000 camera is engineered to operate in extreme environments and fluctuating lighting conditions. It features a fixed 5 mm focal length lens with continuous auto exposure within a specified region of interest, ensuring uniform illumination across images regardless of cavity depth or surface stability. This prevents overexposure or underexposure issues critical for photogrammetric processing.

The camera also supports Precise iris (P-iris) functionality, allowing users to fix the aperture size without additional controls. Combined with Power over Ethernet (PoE), this single-cable solution simplifies integration into TBMs by reducing wiring complexity.

For more information on Prosilica GT cameras and their applications in tunneling projects, visit Allied Vision’s website or contact Geodata GmbH.

Last Updated: 2025-09-04 16:53:20