Theoretical and Experimental Study on Geophone Coupling Medium in Advance Geological Prediction of Tunnel

Tunnel advance geological prediction is an important part of tunnel construction, and accuracy affects tunnel construction’s safety and smooth progress. Studying the geophone coupling medium in tunnel advance geological exploration is critical for improving the accuracy of tunnel advance geological prediction. Through the theoretical modeling of the coupling structure of the tunnel geophone, this paper discusses the role of the coupling medium in the coupling process between the geophone and the surrounding rock. Accordingly, field coupling tests are carried out with five coupling media: industrial butter, paraffin, gypsum, epoxy resin, and clay. Finally, according to the theoretical modeling results, the coupling process of different coupling media is analyzed by employing numerical simulation, and the influence of medium thickness on the coupling effect is discussed. The results show a positive correlation between the coupling effect of the material and its curing strength. The numerical simulation results based on the theoretical formula verify the experimental conclusion. The main factor that the thickness of the coupling medium affects the coupling effect is that the larger thickness will cause more considerable seismic wave loss, and the smaller thickness will produce a more significant resonance phenomenon. The relevant research conclusions can serve the practical engineering application and further improve the accuracy of tunnel advanced geological prediction.