Numerical study of Articulated Concrete Mattresses (ACMs) for offshore pipeline protection

In offshore pipeline projects, inevitably long sections of the transportation pipeline network require protection from natural hazards. Under such environmental conditions, concrete mattresses are recognized as a wellproven technology to surpass challenges in offshore pipeline construction, umbilical deployment and seabed protection/stabilization. To have a better understanding of the physical process of Fluid-Structure-Seabed-Interactions (FSSI) with a ACMs-Pipe-Seabed system, a workable numerical model is proposed to simulate wave-current induced soil responses around the system. Based on the proposed model, this paper discusses the momentary seabed liquefaction near the offshore pipeline and the stability of ACMs. Numerical examples show that ACMs have a significant positive effect on preventing seabed liquefaction around the pipeline by pushing the liquefaction zone to both sides of the shaft. Compared with unprotected conditions, the instability of the protective layer is mainly concentrated in its edge area, and the liquefaction depth can be reduced by around half of the pipe diameter. For the double ACMs-Pipe-System, it is found that the stability of the nearby seabed foundation is related to the mattress spacing and interaction angle.

Automated summary

A numerical model is proposed in this paper to simulate the soil response around an offshore pipeline system under wave-current induction. Numerical examples show that using concrete mattresses can significantly reduce the liquefaction depth and improve the stability of the nearby seabed.