A follow-up feasibility study to an amphibious spray pontoon

Abstract

Beach nourishments or sand replenishments are applied by the use of pipelines or the rainbow method. Replenished sand is then moved and levelled by bulldozers. This is a passive approach to process the outflow of material. The land based equipment is dependent from tides and water levels, and significant effort is required to install and maintain the onshore discharge pipeline. In remote (off-shore) areas mobilization of site equipment to move the sand may be quite a challenge.
The ideal method considers an active approach regarding processing the outflow of material. Instead of distributing the settled material by site equipment, the pipeline out flow point has to be relocated such that the design could be constructed.
To increase workability the pipeline must have the ability to be relocated in water as on land.
Enabling this approach the pipeline system has to be displaced by some sort of means. The main problem is the rigid behavior of the pipeline. Displacement of the pipeline will result that the entire pipeline length has to be displaced. Assuming that in water relocation of a floating pipeline is not that difficult as floating equipment is able to reach the floating pipeline. When the pipeline is situated on land huge pull or push requirements follows when the pipeline needs displacing.

Concepts both for depositing material as for delivering the material have been generated.
The most promising method for depositing material is to apply a spray pontoon. By adding amphibious propulsion technique to the spray pontoon the pontoon is able to work on the interface between water and land.
The most promising method regarding delivering material to the spray pontoon is by applying a steel pipeline.
During depositing the spray pontoon have to be displaced frequently. Also the spray pontoon has to be able to displace the pipeline system. Properties of the pipeline system dictate the required amount of tractive effort that have to be generated by the spray pontoon. Focus is on maximizing the tractive effort to be generated by the spray pontoon.
To decrease the amount of resistance the pipeline will be mounted on platforms. Focus is on minimizing the required amount effort to displace the pipeline system and by generating flexibility along the pipeline system.
By generating flexibility along the pipeline system the pipeline could swing independently of each other. Production figures will determine the amount of flexibility needed along the pipeline system.

It is technical feasible to apply an amphibious spray pontoon but a uniform concept doesn’t exist because there is a large amount of parameters and aspects involved.
It depends on the type of project, and site conditions which type of platform have to be applied. On project locations were small variations of the water level is to be expected and the soil surface has high bearing capacities values platforms can be applied that have an interaction with the soil surface.
However, on soft soils with low bearing capacity values the soil interaction platforms will experience significant sinkage; the resistance force to displace such platforms may possible not be generated by the spray pontoon. In addition on soft soil the spray pontoon is able to generate a smaller pull force compared to when on sandy soil surface.
On (very) soft soils platforms that don’t have an interaction with the soil surface are advantageous compared to soil interaction platforms.