Zusammenfassung: Die Vorauserkundung der geologischen Bedingungen vor der Ortsbrust stellt noch immer eine Herausforderung im Tunnelbau dar und bedarf zusätzlicher Forschung, um die derzeit existierenden Methoden zu erweitern und verbessern. Allerdings gestaltet sich diese Weiterentwicklung auf aktiven Tunnelbaustellen oft schwierig, da sie mit einer Behinderung der Vortriebsarbeiten verbunden ist. Das neu errichtete Zentrum am Berg bietet eine Möglichkeit, diesem Problem zu begegnen. Die maßstäbliche Großforschungsanlage in Eisenerz bietet Raum, um solche Experimente in einer realen Umgebung durchzuführen. Die ersten Daten (Refraktionstomographie, passives seismisches Monitoring, Bohrlochradar) wurden bereits vortriebsbegleitend erhoben. Um die Mächtigkeit der plastischen Zone festzustellen, wurden Bohrlochradarmessungen an zwei radialen Messquerschnitten sowie Refraktionstomographien an zwei Abschnitten entlang der Tunnelwand aufgenommen. Für die Korrelation petrophysikalischer und geotechnischer Parameter wurden darüber hinaus Laborversuche durchgeführt. Das passive seismische Monitoring wurde während des konventionellen Vortriebs eingesetzt, um die Signale der einzelnen Arbeitsschritte zu analysieren und die Eignung des Bohrsignals als seismische Quelle näher zu beleuchten.

No abstract

<p>Geological conditions and their uncertainties are a major risk factor in underground construction projects. To ensure a fast, smooth and save completion of the excavation, a prediction of the geological conditions in front of the working face during tunnelling is a topic of great importance.</p><p>Various geophysical methods for a prediction of the conditions ahead of the tunnel face have been developed over the past years, yet, most of them being seismic techniques, which require a short interruption of the excavation to minimise noise interference. However, there is also the approach with TSWD which uses the working TBM (Tunnel Boring Machine) as a source signal and can thus work simultaneously with the excavation. Up to now, this concept has been applied primarily in mechanised tunnelling and there are hardly any applications in conventional tunnelling.</p><p>In the course of several practical experiments at the “Zentrum am Berg” in Eisenerz (Austria), different concepts for a transfer of TSWD from mechanised to conventional tunnelling were developed and tested at scale in an underground research facility. Three machines were used for these tests, an excavator with a hydraulic hammer attached as well as two different drilling jumbos. The devices were equipped with an accelerometer to pick up the source signal at its origin (pilot signal). Different sensor positions were tested using a sledge hammer as a source and evaluated in detail. Moreover, omnidirectional geophones of different sensitivities (4.5 Hz and 27 Hz) were tested and compared as transducers in the adjacent rock mass.</p><p>An essential part of the experiment analysis consisted of the evaluation of the source characteristics as well as the generated spectral bandwidth of the source signal from typical construction machines in conventional tunnelling. Consequently, the outcomes will be another step forward in the development of a TSWD exploration system also applicable to conventional tunnelling projects.</p>

No abstract

For seismic ahead‐of‐the‐face prediction in tunnelling, sources with known properties are usually used, which, however, are not compatible with NATM. In order to integrate geophysical exploration into conventional tunnelling, the feasibility of construction machinery for generating seismic source signals was investigated. Passive monitoring during conventional tunnelling was used to analyse the seismic signals. Different radiation characteristics of drilling, blasting and bouldering could be identified and their characteristics regarding range and spectrum of the signal could be determined. In subsequent system tests, various machines used in NATM tunnelling were examined for their suitability as sources. The sensor positioning for source signal pickup was evaluated by stroke tests and during ongoing tunnelling operations. For the registration of the waves in the rock mass, different receivers with different geometries were used to characterize the wave field emitted to the front or side of the sources. In addition, the necessary processing steps were determined in order to make these signals usable for an ahead‐of‐the‐face exploration. The results and data form a basis for further development into a practical technical solution for conventional tunnel construction.