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Depth Effect of Rock-Breaking Seismic Source by Drilling Jumbo in Subsea Tunnel with the Drill and Blast Method and Its Application Prospects
Weidong Guo, Zhenyan Tian, Shucai Li, Shaoshuai Shi, Xin Wang and Xiansen Li

The drilling source of a drilling jumbo contains a great amount of noise in the construction of a subsea tunnel, which leads to a large prediction error for the conventional source selection method. To address this problem, this paper proposes an optimization method for the source selection of a drilling jumbo. The optimal truth element is selected for the advanced prediction of a subsea tunnel to ensure the safety of the subsea tunnel construction. First, a spectrum analysis of borehole seismic sources with different drilling depths is carried out, the noise interference contained in the seismic source signal at different drilling depths is analyzed, and the propagation law of a borehole seismic wave field at different depths is studied. Second, the deconvolution-cross-correlation method is used to denoise and reconstruct the seismic records of borehole sources at different depths, and a clutter and signal-to-noise ratio analysis of the reconstructed seismic records is carried out. The principle of optimal selection of the pilot signal time window is established to suppress random noise and surface wave interference. Finally, based on the actual project, the proposed method is evaluated. The results show that when using the optimization method of drilling source interception proposed in this paper, when the drilling jumbo is drilled to the deepest place, the selection of the source signal stationary section for advanced geological prediction is the best. The prediction results are basically consistent with the actual excavation situation, verifying the feasibility and effectiveness of the method.

Keywords: subsea tunnel; drill jumbo; drilling source; drilling depth; earthquake record; timely window selection

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