Seismic exploration in tunneling using full waveform inversion with a frequency domain model

Abstract

With the knowledge of the geology in front of a tunnel, the excavation process can be optimized to avoid damage at the tunnel boring machine and settlements on the surface. Therefore, dwell times can be decreased and additional expenses can be avoided. Transmitted seismic waves will be spread, reflected and refracted due to geological changes. By utilizing geophones, the seismic waves will be captured and information about the geological structure in front of the tunnel can be extracted from the measured seismograms using e.g. the concept of full waveform inversion. A frequency domain model has been employed to demonstrate the potential of full waveform inversion for seismic reconnaissance in a tunnel environment. The success of the inversion procedure depends strongly on the positions of the utilized sender and receiver stations, the chosen initial material parameter distribution, and on the selected frequency groups for the inversion. Further challenges are an accurate representation of the reflecting surfaces and the application of absorbing borders to oppress reflections from the artificial boundaries, which delimit the analyzed domain. The results of the performed full waveform inversion for synthetic models of a 3D tunnel configuration with different disturbances ahead of the front tunnel face will be discussed. Additionally, the influence of different locations of the sender and receiver stations will be analyzed.

Elastic waveform inversion in the frequency domain for an application in mechanized tunneling

“…The potential of frequency domain approaches in the context of mechanized tunneling have only been investigated in combination with the usage of the acoustic wave equation (Riedel et al, 2021b;Wang et al, 2021;Yu et al, 2021), which neglects the dominant influence of shear as well as surface waves. The proposed approach extends the work which has been presented by Musayev (2017) and Riedel et al (2019Riedel et al ( , 2021a. In Comparison to Riedel et al (2021b) the elastic wave equation is used instead of the acoustic wave equation for forward and inverse wave modeling, which increases the complexity of the inverse problem.…”

Propagation Features of Channel Wave Signal in Coal Seam with Scouring Zone

“…The latter model had more obvious reflected waves, which is consistent with the previous discussion. Figure 14 compares the amplitude changes at two points (40, 5, 5), (70, 5, 5) before the scouring zone, and two points after that zone (100, 5, 5), (130,5,5).…”

“…However, few have tackled the influence of small structures, e.g., scouring zone, on the propagation features of the wave [4]. The propagation features of elastic waves are usually analyzed by the elastic wave equation and geological methods [5][6][7].…”