隧道勘探AMT数据二维非线性共轭梯度反演的关键参数探讨

研究了二维非线性共轭梯度反演对于铁路隧道音频大地电磁(AMT)勘探的适应性。通过模型反演实验,确定控制反演进程的关键参数选取方法,以便于在不损失分辨率的前提下避免假异常。实验结果表明,在类似的地电条件下:①采用TE+TM模式联合反演;②使用浅部细分网格以更好地拟合地形;③不使用1000 Hz以上易受干扰的数据;④使用较小的正则化因子;⑤选用中、浅层电阻率的均匀空间作为初始模型;以上这些手段能提升反演结果的准确性,更适应铁路隧道勘探解释需要。

Researches on the selection of key parameters in AMT 2D nonlinear conjugate inversion for railway tunnel exploration

In this paper,the authors analyzed the suitability of 2D nonlinear conjugate inversion method in railway tunnel AMT exploration under complex topographic and geological conditions.Based on typical modeling and inversion research,researchers can find out the best key parameters to control inversion algorithm so as to avoid fake abnormalities shown on inversion results.Researches show that 2D nonlinear conjugate inversion works well in railway tunnel AMT exploration.If the true model is like the model type described in this paper,inversion result can be efficiently improved by inverting TE&TM mode data,inverting frequencies less than 1000 Hz,using small smooth factor and choosing the half space initial model close to the shallow layers'resistivity.