Research On Forward Modeling Of Magnetic Anomalies And Potential Field Transformations Of Underground Pipelines

Due to historical reasons,some underground pipeline data is not perfect enough or even wrong or missing,which may easily lead to accidents such as digging or leaking pipelines during the construction process.Therefore,it is extremely important to detect the direction,center and buried depth of underground pipelines.Most of the underground pipelines are iron pipes,and their magnetic susceptibility is greatly different from the surrounding medium,so they can be effectively detected by the magnetic method.This paper is divided into two parts: magnetic anomaly forward modeling and potential field transformation.Firstly,two magnetic anomalies’ forward algorithms of pipelines are introduced: the magnetic dipole algorithm based on superposition of microelements and the line integration algorithm based on Poisson’s formula.The calculation accuracy and rate of the two algorithms are compared,the results indicate that the average relative error of the two magnetic anomalies is about 0.01%,which can be regarded as the same precision.The line integration algorithm does not need to divide and reconstruct the pipeline,it is more efficient in calculation rate,and can directly obtain the analytical expression of the magnetic anomaly,so its parameter influence is more intuitive.In order to locate the horizontal position and buried depth of the pipeline more efficiently and conveniently,this paper proposes to use The Feature Point method for inversion.Because the magnetic anomaly formula is too complicated during oblique magnetization,and the analytical solution of the characteristic points during vertical magnetization is directly obtainable and relatively simple,so this paper carried out the frequency-domain potential field conversion: magnetic anomaly component conversion,RTP and homologous gravity anomaly conversion,to obtain the magnetic anomaly and gravity anomaly data during vertical magnetization.By selecting the coordinates of the feature points,the horizontal position and burial depth of the pipeline can be directly observed or calculated.