The Role of Physical Modelling in a Port Expansion Project in a Complex Wave Environment

Abstract: This paper describes the role of physical modelling in the design and development of a port expansion project in Peru. Terminal Internacional Del Sur S.A. (TISUR) is expanding Matarani Port in Peru to include a new general cargo terminal (Terminal G) as well as modify an existing terminal used to export dry bulk materials where ship motions have been excessive in the past and currently use multi-buoy moorings (Terminal F).
Matarani Port is situated on the coast of Peru and is subject to moderate swell activity. Prevailing wave conditions are incident from a relatively narrow band of directions. However, the nearshore waves are heavily influenced by reflections from the steep and uneven cliffs that form the shoreline, as well as a very irregular and steeply sloped nearshore bathymetry consisting of several emergent or slightly submerged offshore islands. The resulting wave pattern in the vicinity of the port is highly complex, and current numerical tools would struggle to describe the wave climate and its effects on moored vessels confidently.
The physical model study sought to verify safe vessel operations at the port, employing two modelling phases. The first phase simulated port terminals with moored ships to assess loads and motions, ensuring operational efficiency without berth downtime (moored ship response tests). Terminal modifications were proposed, including changes to mooring configurations, utilization of constant tension mooring elements, Terminal G's repositioning, and installing a sheltering breakwater for wave protection. The second path investigated breakwater stability and coastal structure performance under storm and extreme wave conditions, essential for maintaining port resilience.
The study utilized the National Research Council of Canada’s Large Area Basin at a 1:45 scale, incorporating bathymetry, port features, scaled vessels, mooring arrangements, and coastal structures such as breakwaters. Of particular note was the development of novel, model scale simulators that can replicate the dynamic nature of constant tension mooring elements capable of paying out and paying in at two different line tensions. Several simulators were deployed and their performance at reducing line and fender forces, as well as ship motions were examined. Instrumentation measured wave conditions, vessel motions, fender and mooring line forces, enabling detailed analysis. Moored ship response tests simulated operational conditions, focusing on wave-induced movements, fender loads, and line tensions. Breakwater stability tests simulated yearly storms and extreme wave events, assessing proposed structure performance under varying conditions.
This physical model study played a key role in the engineering design of the port expansion, and the results were crucial in assessing various alternatives, optimizing preliminary designs, and validating the layout, costing, and construction of the facility. Moreover, the physical model was able to model the highly complex wave interactions with the steep and irregular shoreline and their effect on the moored vessels, as well as the highly complex constant tension mooring systems with a higher degree of certainty than just numerical tools alone. The study's findings were instrumental in finalizing and de-risking the project's design, ensuring its resilience, cost-effectiveness and efficiency.

How does this project / topic contribute to the advancement of the industry and profession?: Well-designed 3D physical models provide very accurate simulations of nearshore wave transformations and wave-structure interaction. Due to the highly irregular bathymetry and shoreline, wave modelling at this location using numerical tools alone would bestow a relatively high level of uncertainty. Moreover, the current numerical models could only represent the highly complex dynamic mooring systems in a simplified manner making this uncertainty grow. This paper demonstrates a case where a physical model was essential to evaluate a complex mooring system in a complex wave environment.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: Dynamic, or constant tension, mooring elements are still relatively new infrastructure pieces globally. Simulators that can replicate these devices at model scale are very novel, with few known systems in the marketplace today. Several of these devices were custom built and used for the first time for this model study. The authors are not aware of any other publication detailing the use of constant tension mooring simulators at model scale.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: Developing the constant tension mooring systems was a complex endeavour. The use of these systems in the field is still relatively new, and the standard information/setup received from vendors regarding the performance characteristics had to be modified and improved to achieve the expected performance at full scale, and the project required significant effort to understand, model, tune and optimize the characteristics of these system.

Who is the target audience for this paper?: This paper is intended to assist engineers and port owners with understanding the analysis methods that are available for complex mooring scenarios using dynamic and/or constant tension mooring elements, which are becoming more common in port development. In particular, this paper would be helpful for anyone facing complex wave patterns due to steeply sloped and highly irregular bathymetry, or who has or should consider whether physical model testing would benefit their project.