Marine cable-body systems deployed from surface support vessels are widely used in ocean mining. The present paper addresses their dynamic heave response under severe external excitation due to the heave motion of the surface support vessel. A single-degree-of-freedom model and a multi-degree-of-freedom model are presented. The former is to reveal the fundamental characteristics of the system under extreme excitation while the latter is for predicting the snap loading in the cable. The numerical examples illustrate that under such excitation the dynamic response of marine cable-body systems can lose its stability and become chaotic.
Marine cable-body systems, deployed from and attached to surface support vessels, are widely used in ocean mining operations. In these, the dynamic response and the level of tensile loading under which the marine cable-body system is operated is of particular interest both to designers and operators from the point of view of safety, effectiveness and efficiency. To ensure system integrity, the cable tension needs to be limited, or a limiting condition must be imposed such as, for example, a maximum operational seastate. It is, therefore, of great practical importance to be able to predict with confidence the dynamic response and the maximum cable tension of marine cable-body systems and to provide guidelines for design and operational purposes. If the marine cable-body is deployed in a weak current, or it is constrained by taut vertical guide lines, the whole system can be approximated as a one-dimensional problem and only the heave motion needs to be considered. An inherent feature of marine cables is that they Calmot resist compressive loading. The allowable tension is related to the break strength of the cable, whereas avoiding zero tension is directed at preventing the taut-slack condition and its associated snap loading. However, avoiding zero tension is not always attainable.