Safety assessment of submarine power cable protectors by anchor dragging field tests

Abstract

A safety assessment of mattress type submarine power cable protectors under dragging forces of a 2-ton anchor was carried out through field tests. These cable protectors were designed to adjust their size by controlling the number of reinforced concrete blocks. In the field tests, soil properties on a target site were simulated and the safety assessment of the protectors was made through five different dragging scenarios. For the safety assessment, a safety width (1m) was considered; hence, the failure assessment was made if the anchor or broken blocks invaded the width. It is shown that the mattresses with five columns were not safe because of the relatively narrow width (2.5m) but, thanks to a wider width (3.5m), the mattress with seven columns acquired the safety in most cases. However, the seven-column mattress was not safe under a relatively smaller dragging angle (60°) because the horizontal displacement was significant and accordingly the anchor arm reached the safety width. In addition, it is shown that the failure of the concrete block was initiated by the breakage of the connecting hooks. Therefore, it is desirable for safety assurance to adjust the strengths of the hooks and concrete blocks and their array.