Study on Structural Configuration Design and Dynamic Characteristics of Deep Sea Flexible Riser in Deep Sea Mining System

Abstract As mining operations extend into deeper oceanic regions, traditional rigid riser systems are increasingly susceptible to fatigue damage, prompting a shift toward flexible riser systems. This study investigates the structural configuration design and dynamic characteristics of a carbon fiber composite flexible riser for deep-sea mining applications. The development and working principle of deep-sea mining systems are first introduced. The analysis of the flexible riser combines theoretical, numerical, and experimental approaches, integrating global and local perspectives. Using Orcaflex software, an 8-layer carbon fiber composite flexible riser is equivalently modeled to compare the global mechanical responses—including tension and bending moment—of four configurations: catenary, lazy wave, steep wave, and double wave. Results indicate that the carbon fiber riser offers high strength and lightweight properties, extending system service life and enabling operation in broader mining fields. The double-wave configuration demonstrates superior mechanical performance and greater adjustability through buoyancy module parameter optimization. Further analysis examines the influence of buoyancy configuration, anchor point location, internal ore content, and water depth on the dynamic response of the double-wave riser. The global mechanical parameters derived provide valuable reference for cross-sectional analysis in practical engineering applications. Mutual validation between global and local mechanical assessments confirms that the carbon fiber flexible riser is structurally viable for real-world deep-sea mining conditions over its full service life.