Seismic forward-prospecting in tunnels is an important step to ensure excavation safety.Nowadays,most advanced imaging techniques in seismic exploration involve calculating the solution of elastic wave equation in a certain coordinate system.However,considering the cylindrical geometry of common tunnel body,Cartesian coordinate system seemingly has limited applicability in tunnel seismic forward-prospecting.To accurately simulate the seismic signal received in tunnels,previous imaging method using decoupled non-conversion elastic wave equation is extended from Cartesian coordinates to cy-lindrical coordinates.The proposed method preserves the general finite-difference time-domain(FDTD)scheme in Cartesian coordinates,except for a novel wavefield calculation strategy addressing the sin-gularity issue inherited at the cylindrical axis.Moreover,the procedure of cylindrical elastic reverse time migration(CERTM)in tunnels is introduced based on the decoupled non-conversion elastic wavefield.Its imaging effect is further validated via numerical experiments on typical tunnel models.As indicated in the synthetic examples,both the PP-and SS-images could clearly show the geological structure in front of the tunnel face without obvious crosstalk artifacts.Migration imaging using PP-waves can present satisfactory results with higher resolution information supplemented by the SS-images.The potential of applying the proposed method in real-world cases is demonstrated in a water diversion tunnel.In the end,we share our insights regarding the singularity treatment and further improvement of the proposed method.

Yuxiao Ren;Jiansen Wang;Zhichao Yang;Xinji Xu;Lei Chen

Geotechnical and Structural Engineering Research Center,Shandong University,Jinan,250061,China;School of Qilu Transportation,Shandong University,Jinan,250061,China

岩石力学与岩土工程学报（英文版）

[1]Yuxiao Ren;Jiansen Wang;Zhichao Yang;Xinji Xu;Lei Chen-.Pre-stack elastic reverse time migration in tunnels based on cylindrical coordinates)[J].岩石力学与岩土工程学报（英文版）,2022(06):1933-1945

gularity,CERTM

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