Traction Response and Operational Risk of a Drag-Reduction System for HDD Submarine Cable Pulling Based on Local Full-Scale Experiments

Abstract

This study investigates the traction response and operational risk of a compact ball-frame and tensioned-steel-cable drag-reduction system for submarine cable pulling inside HDD steel casings, based on local full-scale experiments. Thirteen test cases were designed by considering pipe curvature, device spacing, terminal reaction-force loading mode, and dry or sand–slurry in-casing conditions. In addition to the equivalent friction coefficient, three response descriptors, namely, the average traction force, peak coefficient, and fluctuation coefficient, were introduced to evaluate mean resistance, peak amplification, and process stability. The results show that pipe curvature significantly amplifies both traction peaks and response fluctuations, and should therefore be regarded as a key factor governing operational risk. The effect of device spacing is environment-dependent: under dry conditions, a moderate reduction in spacing improves rolling continuity, whereas under sand–slurry conditions, excessively dense deployment may aggravate local obstruction and response fluctuation. Stronger terminal reaction-force loading also increases peak amplification and instability. Based on these findings, a case-specific and experiment-oriented framework for operational-risk classification is proposed. The present results are intended to support traction-response characterization, device arrangement, and construction control under representative local conditions, rather than to replace full-scale field validation.

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