Abstract As an efficient and non-destructive geophysical detection tool, ground penetrating radar (GPR) is wide? ly used in the detection of tunnel geological hazards, especially tunnel cavities. Due to the constraints of environmental conditions, the current GPR measurement methods used in tunnelling are mostly based on 2D reflection profiles,which results in the problem of large limitations on the spatial detection range. In order to improve the spatial detection range of GPR as much as possible without increasing the workload or reducing the efficiency of data acquisition,this paper proposes a detection mode based on half-space scanning measurement, by which it achieves the omnibearing 3D imaging within 30 m range of the half-space area of the tunnel face by the inversion of 3D data volume.The proposed method is verified by 3D FDTD numerical simulation analysis based on CPML absorbing boundary conditions and by spectral analysis on the received signals. The method is applied to the detection of cavities in the right tube of Ying'erling tunnel of Rongcheng-Wuhai Expressway in Hebei Province, successfully detecting the cavity hazards at the top of the tunnel from K103+607 to K103+567. In addition, the 3D GPR detection results are cross-validated with the 3D seismic geology prediction results, with good consistency.
Abstract：
As an efficient and non-destructive geophysical detection tool, ground penetrating radar (GPR) is wide? ly used in the detection of tunnel geological hazards, especially tunnel cavities. Due to the constraints of environmental conditions, the current GPR measurement methods used in tunnelling are mostly based on 2D reflection profiles,which results in the problem of large limitations on the spatial detection range. In order to improve the spatial detection range of GPR as much as possible without increasing the workload or reducing the efficiency of data acquisition,this paper proposes a detection mode based on half-space scanning measurement, by which it achieves the omnibearing 3D imaging within 30 m range of the half-space area of the tunnel face by the inversion of 3D data volume.The proposed method is verified by 3D FDTD numerical simulation analysis based on CPML absorbing boundary conditions and by spectral analysis on the received signals. The method is applied to the detection of cavities in the right tube of Ying'erling tunnel of Rongcheng-Wuhai Expressway in Hebei Province, successfully detecting the cavity hazards at the top of the tunnel from K103+607 to K103+567. In addition, the 3D GPR detection results are cross-validated with the 3D seismic geology prediction results, with good consistency.
DENG Haiming1 YANG Xi2 LI Zhishan3 LEI Hongxian4 TANG Kan1 FAN Mingwai2 ZHANG Hantao2
.A 3D GPR Imaging Technique of Tunnel Cavities Based on the Half-space Scanning Measurement Mode[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(3): 52-59
2021, Vol. 58 