ABSTRACT

The increasing demand for continuous risk assessment in civil engineering has led to the development of seismic exploration systems for tunnel excavation. On such system is the Integrated Seismic Imaging System (ISIS) that has been developed at the GFZ. In contrast to comparable systems, ISIS can be used on any type of tunnel excavation in soft rock as well as in hard rock tunneling. Based on ISIS, the OnSITE project focuses on new hardware for integrated measurements during underground excavation, modelling and processing of data measured under these specific circumstances and the interpretation of the seismic result with various data sets (geological mapping, TBM parameters). The hardware development has generated wireless data logger for underground work and new seismic sources for the exploration of the seismic results was combined with TBM parameters and geological mapping showing remarkably good results.

1 INTRODUCTION

The development of modern infrastructure necessitates an increasing amount of tunnel excavation in setting with varying geological background. The success of such ventures is strongly depending on an accurate prognosis of the host rock' geological behaviour. So far, high resolution data has been retrieved before the actual excavation via exploratory wells. This data is valid only for restricted areas. On the other hand surfaces investigations like geological mapping and seismic profiling cover broader areas with lower resolution. Recently, the use of subsurface geophysical methods increases, the most important one being seismic exploration during tunnel excavation. These seismic methods aim at generating a high resolution image of the geological contracts directly along the projected roadway (Kneib et al. 2000; Otto et al. 2002). The methods commercially available so far are restricted to either hard or soft rock tunneling due to their generation. Consequently, the field of application for these systems is limited and a wide gap is left where tunnel construction work takes place in geologically complex areas. Through this is exactly where seismic surveys would be especially useful. To overcome these limitations a new integrated seismic interpretation system (ISIS) has been developed at the GFZ (Borm et al. 2003). ISIS includes a non-intrusive seismic acquisition system as well as processing and imaging tools. The acquisition system is relying on the desired direction ahead of the tunnel (Bohlen et al. 2007). In order to enable the implementation on an industrial scale, further research is needed to enhance the hardware and interpretation system. Hence, the objective of the collaborative research project OnSITE (On-line Seismic Imaging for Tunnel Excavation) is to enhance seismic acquisition, gain knowledge about a tunnel the ware field propagation tool for tunnel excavation. To achieve these key aspects of seismic underground measurements the project has focussed on:

  • Modeling and processing of data measured with ISIS for a better understanding of the seismic wave field

  • Development of hardware for seismic acquisition in underground construction.

  • Interpretation of seismic data collected with ISIS using a multivariate data set.

The research in this project is carried out at the University of Freiberg, the Free University of Berlin.

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