井间电磁波CT不同初始模型成像效果对比

Comparison of Imaging Effects of Different Initial Models of Cross Hole Electromagnetic Wave CT

井间电磁波CT成像是一种高效探测地下介质电磁特性的地球物理方法,广泛地应用于工程地质勘察中,其成像结果受多种因素影响,其中关于初始网格模型对成像质量的影响情况讨论不多。本文以溶洞模型为例在正演模拟数据的基础上,给出三种不同的吸收系数网格初始模型,利用联合迭代法(SIRT)进行反演成像,得到三种网格初始模型下反演结果,将反演成像结果与原始模型进行对比分析。结果表明,三种网格初始模型的反演结果均能较好地反应异常体,其中采用BPT反投影结果作为初始模型反演效果最好,水平测线值模型次之,平均值法效果较差。将三种初始模型用于实际工程的井间电磁波CT反演中,结合地质勘察钻孔对比分析,结果与模拟分析结果一致,为今后层析成像的结果解释和判断提供借鉴和依据。

Cross hole electromagnetic wave CT imaging as a geophysical method for detecting the electromagnetic characteristics of underground media is widely used in engineering geological exploration.Its imaging results are affected by many factors,of which the influence of the initial grid model on the imaging quality is rarely discussed.In order to analyze the influence of different initial models on the imaging quality,this paper introduces three initial models of absorption coefficient based on the forward simulation data of the karst cave model,then uses the joint iteration method(SIRT)to carry out inversion imaging,and obtains the inversion results under the three grid initial models.The inversion imaging results are compared and analyzed with the original model,which indicates that the inversion results of the three grid initial models can better reflect the anomaly body,and the BPT back projection results as the initial model have the best inversion effect,the horizontal line value model takes the second place,and the average method has the poor effect.When the three initial models are used in the cross hole electromagnetic wave CT imaging of the actual project,the results are consistent with the simulation analysis results in combination with the comparative analysis of the geological survey boreholes,which can provide reference and basis for the interpretation and judgment of the tomographic results in the future.