一种基于半空间扫描测量模式的隧道坍腔地质雷达三维成像技术

A 3D GPR Imaging Technique of Tunnel Cavities Based on the Half-space Scanning Measurement Mode

地质雷达作为一种高效、无损的地球物理探测手段,被广泛应用于隧道地质灾害尤其是隧道坍腔的探测中。由于受环境条件的制约,目前隧道中地质雷达探测方式多以二维反射剖面为主,存在空间探测范围局限性较大的问题。为了在尽量不增加工作量、不降低数据采集效率的前提下,尽可能的提高地质雷达的空间探测范围,文章提出了一种基于半空间扫描测量的探测模式,通过对三维数据体的反演实现了隧道掌子面半空间区域30 m范围内的全方位3D成像。通过基于CPML吸收边界条件的三维FDTD数值模拟分析以及对接收信号的频谱分析,验证了该方法的有效性。将该方法应用于河北省荣成—乌海高速公路营尔岭隧道右洞坍腔检测中,成功探测到里程K103+607~K103+567区域内隧道顶部的坍腔危害。此外,将三维地质雷达探测结论与三维地震地质超前预报结果进行交叉验证,吻合效果良好。

As an efficient and non-destructive geophysical detection tool,ground penetrating radar(GPR)is widely 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.