Anchor Drop Tests for a Submarine Power-Cable Protector

Abstract

AbstractSubmarine power cables are widely used for power transmission, such as between mainlands and offshore islands and from offshore wind farms to on-land substations. There are several ways to protect power cables from accidental loads. Protection includes concrete blankets, sand bags, bundles, tunnel-type protectors, and trenching. However, no design standard for power-cable protectors is currently available because of the varieties of cable protection solutions and man-made or natural hazards to submarine power cables. Thus, this paper presents anchor drop tests for a newly designed, matrix-type submarine power-cable protector assembled with reinforced concrete blocks, to make a safety assessment. Marine environments were surveyed at the target site and simulated in the test set-up. A 2-ton stock anchor was selected as the colliding object, and a 25-ton crane was prepared to drop the anchor. Preliminary tests were performed to investigate the effect of soil composition and protector arrangements on the test results. Finally, four field anchor drop test scenarios were designed, carried out, and analyzed, and a safety assessment was made for the submarine power cable. From the tests, it was found that, in addition to falling distances, the soil composition and saturation were significant factors for the settlement depth and damaged areas. Considering the settlement depth of soils, the damaged areas of the concrete blocks, and the damaged state of the pipes (safety zone), all of the test results showed that the mattress failed to protect the power cable from the anchor collision. The deformation, damage, and breakage of the pipe, which simulated the safety zone of the power cable, gave clues as to the reasons for the failure.