Method for rapid localization of dam leakage passage based on gradient measurement of total magnetic field

A method for rapid localization of a dam leakage passage based on gradient measurement of a total magnetic field, comprising the following steps:

• step S101:
• separately deploying a power supply electrode at an outlet of a leakage passage on a downstream face of a dam and at a position having a certain distance away from an upstream face of the dam, and applying current signals of different frequencies to establish a current loop, so as to form a current passage within the leakage passage;
• step S102:
• designing a gradient observation device based on magnetic sensors, with an observation height difference of the magnetic sensors being Δh, and utilizing the gradient observation device to observe a magnetic field component generated by the current passage;
• step S103:
• deploying an observation profile in a direction perpendicular to the leakage passage, and performing three-component magnetic anomaly observation using the gradient observation device;
• step S104:
• calculating total magnetic field anomaly values at different observation heights using three-component magnetic anomaly values obtained in step S103, and calibrating a lateral position of the leakage passage on the basis of a total magnetic field anomaly intensity;
• step S105:
• calculating a longitudinal burial depth of the leakage passage on the basis of the total magnetic field anomaly values at different observation heights corresponding to the lateral position of the leakage passage in step S104, and calibrating a longitudinal position of the leakage passage, wherein
• steps for calibrating the lateral position of the leakage passage are as follows:
• calibrating a lateral position of the current passage on the basis of spatial coordinates corresponding to maximum total magnetic field anomaly values Hmax at different frequencies;
• and
• steps for calibrating the longitudinal position of the leakage passage are as follows:
• calculating the longitudinal burial depth of the leakage passage on the basis of total magnetic field intensity values Hlow and Hhigh corresponding to the lateral position, with the calculation formula being as follows:
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• where Δh is a longitudinal height difference between two magnetic sensors, h is a burial depth of the leakage passage, Hhigh is a total magnetic field intensity measured at a higher position, and Hlow is a total magnetic field intensity measured at a lower position;
• and
• step S106:
• determining an inlet of the leakage passage by combining the laterally calibrated position in step S104 with the longitudinally calibrated position in step S105, achieving precise localization of the leakage passage.