Identification of Unexploded Ordnance and Buried Objects by Use of a Marine Emi Sensor at the Fehmarn Belt Tunnel Project
WODCON XXIII - Dredging is changing - The Practice. The Science. The Business.
M.Schwartz, S.D. Billings
"In order to tackle the threat posed by remnants of war in the area of the Fehmarn Belt Tunnel project prior to commencement of dredging activities, a multi-component electromagnetic induction sensor for ROV based investigation and identification of marine UXO (SubTEM-ROV) was used. The system consists of a single transmitter coil and nine receiver coils. It was deployed to minimize the number of necessary object excavations during the project's identification and clearance campaign. During survey, the electromagnetic polarizabilities of the buried objects were determined by an inversion algorithm. The resulting parameters of size" and "decay" were used to compare the object against the smallest UXO that constitutes a threat to dredging operations. Thus it was possible to classify these objects as either those that pose a substantial threat or those that do not pose a threat to the following dredging operations. The analysis of the objects allowed for a significant reduction in necessary excavation works. Out of 1514 objects that showed an anomaly on the electromagnetic survey 850 objects were identified as being too small to require excavation and relocation. By application of this method the identification and clearance operation was shortened by approximately 26 days."
Keywords: transient electromagnetic sensor, TEM, unexploded ordnance detection, UXO, marine unexploded ordnance