The geological survey of Mengjiaya deep-buried tunnel of Yifu railway was carried out by using the space-time array hybrid source electromagnetic method. This method integrates the advantages of natural and artificial field source electromagnetic exploration, and uses a unified theoretical model and observation equipment. It can collect three types of exploration data: remote reference magnetotelluric, controlled source magnetotelluric and wide-area magnetotelluric data in one arrangement, which will greatly improve field work efficiency and exploration accuracy. The anti-interference algorithm designed for the strong interference area was used for fine denoising, and finally the nonlinear conjugate gradient method (NLCG) and the lateral constrained quasi-two-dimensional (LCI) method were used for inversion. The inversion results were consistent with the geological data. At the same time, combined with the existing geological data, it is inferred that the shallow strata of the Mengjiaya tunnel are layered, low-resistivity Permian Qixia Formation limestone intercalated with coal strata. The deep strata are limestone, shale and quartz sandstone. There is a fault in the middle of the survey section (surface mileage CK172+875 section), and the surrounding rock mass is relatively broken. The exploration results are of great significance in guiding the next step of safe construction of the tunnel.

space-time array  /  tunnel  /  electromagnetic method  /  signal de-noising  /  NLCG inversion  /  LCI inversion