音频大地电磁在长大深埋隧道勘探中的研究与应用

Research and application of audio magnetotelluric in deeply-buried tunnel exploration

以成昆线民太隧道岩石物性特征为基础,结合实际地质背景,针对隧道勘察中断层、含水破碎带、岩溶等地质目标体的埋深、规模等问题,建立相应的地质模型,开展正反演模拟计算,进行对比分析,探讨音频大地电磁法对隧道勘探目标的有效性及可行性,旨在提供合理的模型依据和反演参数。分析对比两种极化模式正演数据,TE模式视电阻率资料反映的结果更接近真实情况,TE与TM相位资料具有一定的参考价值。选择不同初始模型的多反演参数对模型进行反演计算,最终确立了以一维Occam-TE反演作为初始模型对成昆线民太隧道实测数据进行二维NLCG-TE+TM反演,结果证明了模型的合理性和反演参数选择的有效性。

On the basis of petrophysical properties of Mintai tunnel in Chengdu-Kunming line,combined with the actual geological background,in allusion to buried depth and scale of geologic exploration target such as the fault、water-bearing fracture zone and karst in tunnel exploration,this paper establishs corresponding geological model,carry out forward and inversion simulation,comparative analysis,to discusses the effectiveness and feasibility of the audio magnetotelluric method in tunnel exploration,aims to provide reasonable model and inversion parameters.From analysis of the forward modeling datas of two polarization mode,TE mode reflect the results of the apparent resistivity data closer to the real situation,and TE and TM phase information has reference value.Through choosing different initial model for inversion calculation of the model,in consideration of forward modeling analysis and geological survey of the study area,this paper finally establishs to invert the measured data of Mintai tunnel by two-dimensional NLCG-TE+TM inversion in a one-dimensional Occam-TE inversion as the initial model.The result proves the rationality of the model and the effectiveness of the proposed inversion parameter selection.