Hybrid Induction Sensing Method for Detection of Underground Cable Lines and Pipelines

The analysis of the principles of searchers construction was carried out. It was found that induction route methods based on measurements of secondary electromagnetic fields, which are created by currents induced in a cable by independent radiating systems using third-party power sources, have received the greatest use. For the implementation of these methods, radiating systems of various types are used, such as frame or vibrator antennas. When building locators, the mutual distribution of the receiving and transmitting coils is of particular importance. The research group considered options for the mutual arrangement of the coils. It was found that when building a track finding equipment, two basic methods of control are widely used: the response method of the electromagnetic field parameters to the internal or surface impedance of the medium when the electromagnetic field propagates in or above the ground, respectively, and the input impedance response method of the receiving frame on the electromagnetic properties of the medium being probed. Based on the features of these two methods, a new hybrid method of induction sounding was proposed, which actually combines these two methods. When implementing this hybrid method, an induction probe (IP), which is an induction transducer of a magnetic field into an electrical signal, contains a receiving ferrite antenna (FA) and a loop antenna (LA), and LA combines the functions of transmitting and receiving antennas. A design variant of an IP with coplanar placement of FA relative to LA, which provides full geometric compensation of the primary field, is proposed. When IP operates, information is recorded on one information channel from LA (the current value of the amplitude of the exciting current) and on two information channels from the FA (current values of the amplitudes of the voltages of the active and reactive components of the output signal of the FA, respectively). The implementation of such information redundancy significantly increases the information content, efficiency and reliability of the proposed hybrid method.

Towards an estimation of sub-sea-ice platelet-layer volume with multi-frequency electromagnetic induction sounding

Ice-platelet clusters modify the heat and mass balance of sea ice near Antarctic ice shelves and provide a unique habitat for ice-associated organisms. The amount and distribution of these ice crystals below the solid sea ice provide insight into melt rates and circulation regimes in the ice-shelf cavities, which are difficult to observe directly. However, little is known about the circum-Antarctic volume of the sub-sea-ice platelet layer, because observations have mostly been limited to point measurements. In this study, we present a new application of multi-frequency electromagnetic (EM) induction sounding to quantify platelet-layer properties. Combining in situ data with the theoretical response yields a bulk platelet-layer conductivity of 1154 ± 271 mS m–1 and ice-volume fractions of 0.29-0.43. Calibration routines and uncertainties are discussed in detail to facilitate future studies. Our results suggest that multi-frequency EM induction sounding is a promising method to efficiently map platelet-layer volume on a larger scale than has previously been feasible.