Meeting Requirement 3 – Part A
If Requirement 1 and 2 are relatively modest and achievable with small increases in funding and coordination across government departments, Requirement 3, is not.
It would represent a significant improvement over anything in service anywhere today and be a unique capability, one that is hugely ambitious.
Meeting Requirement 3 would certainly produce a capability in excess of UK requirements but instead, a ‘signature system’ for multinational operations in conjunctions with allies.
Whether it is a UK funded or multinational funded project, we can discuss, but we do need to cast our eyes wider when discussing it.
There are three parts to the discussion on meeting Requirement 3;
- Existing systems
- Pierhead, pier and shore interface
- Wave attenuation
We can visualise Requirement 3 as a modern Mulberry Harbour, with knobs on.
The most obvious starting point for ideas to meet Requirement 3 would be to examine existing solutions and previous research projects.
JLOTS ELCAS Pier
The US Joint Logistics Over The Shore (JLOTS) is defined as;
The process of loading and unloading ships without the benefit of deep draft-capable, fixed port facilities
ELCAS was part of a wider programme, Container Off-loading and Transfer System or COTS, ELCAS being a subsystem.
It came into service with the US armed forces in the late seventies and was specifically designed to transfer containers and equipment, but mostly containers, in the follow on phase of an amphibious assault, similar to Requirement 3.
The objective for ELCAS was (and is) to avoid having landing craft and barges enter the surf zone.
Initial testing and concept studies recognised that its significant volume would displace equipment intended for the USMC and therefore, unlikely to find a home on USN amphibious shipping, hence the drive to deploy it on civilian and MSC shipping, especially SeaBee and LASH barge carriers, the LASH carrier being proven to have many advantages over the SeaBee. These tests also included using something called the Lightweight Modular Multi-Purpose Spanning Assembly or LMMSA which allowed a RORO ship to interface with ELCAS.
ELCAS modules were originally modified Navy Lighterage pontoon causeway units connected by a hinged ‘flexor pin’. Once the causeway modules had been manoeuvred into place and connected together using the flexor pin they were ready for elevating. Each module had a series of internal or external spud wells and the piles were inserted into these spud wells and then jacked up to the required working height.
The ELCAS pier head is simply another row of causeway modules.
A fender string was installed to resist berthing forces and provide some measure of standoff that allowed the 140-tonne crawler crane to lift containers from the lighter to an awaiting truck and trailer. The piles used for the fender string are pointed instead of hollow to allow them to be driven deeper than the normal piles.
Because the pier head was not wide enough to allow a truck to turn the 180 degrees needed a motorised turntable at the seaward end of the pier head was used, ingenious I think.
At the beach end, a pair of ramps were used to transition from the pier causeway to beach.
The main problem with the original ELCAS was that because the causeway sections and piles had the be assembled on the water before jacking up, the whole thing was very susceptible to wind and waves limiting construction sea state. It was also very labour intensive and therefore, not very quick to install. Because the deck was frequently overtopped by waves it was wet and hazardous when operating cranes.
Recognising these shortcomings and because of the physical condition of the ELCAS stock a decision was made to replace it, the new system coming into service, after a number of contract problems, in the mid-nineties. Instead of jacking floating modules out of the water ELCAS-M uses a cantilever method to build out from the beach, without the deck modules touching the water, and thus, practically immune from wave conditions.
A number of alternatives were proposed and some initial testing conducted, these included a high wire transfer and aerostat system, neither was adopted.
First used on operations during the 2003 operation to invade Iraq the ELCAS-M was used to augment an existing Kuwaiti naval base, providing additional loading and unloading capacity in support of the build-up phase.
Apart from the method of construction, the ELCAS-M design was not that much of a change from ELCAS.
The beach ramps are grounded into an excavated area above the high water mark called a ‘duck pond’ that is 9 meters wide by 8 meters long.
The 40 foot by 8 foot ISO container sized modules are supported on 2 feet diameter hollow steel piles that are driven in during construction as the causeway is assembled from the beach to the sea. The piles are driven in sequence and modules attached until the required length is achieved. Individual piles are 30 foot long and welded together as they are driven, usually between 10m and 12m depth. Softer soil conditions will require longer piles to be used, in Kuwait for example, many had to be 30m long to achieve sufficient load bearing strength. Two pile drivers are used, one driving and one positioning.
The full ELCAS-M system requires 193 piles.
In order to accommodate two-way vehicle traffic, the pier is 24 feet wide. When the piles are driven to the correct depth they are pinned to the module and cut off flush to avoid interfering with traffic and crane operations. The pier head is wider to accommodate two 200 tonne cranes and two turntables that allow trucks to be turned within their diameter which negates the need for vehicles to reverse along the full length of the pier.
Lighting is also installed to allow 24×7 operations, together with safety restraints and power generation (total 260kW split between 4 generators)
It can be built out to a maximum length of 915m and takes on average between 7 and 14 days to build, depending on pier length. In optimal conditions, the maximum stated throughput is 370 TEU per 24 hour period or about 15 per hour.
It is worth re-emphasising, the build sequence is to land the components on the shore using a combination of landing craft and barges, and the pier built out from the beach to the sea.
The fender strings shown above alleviate some of the lateral forces between ELCAS and the lighter, they are the same size as normal ELCAS modules but only one wide. Elevating the pier head
It should also be noted that the ELCAS-M system is not designed to accommodate large ships but lighters, small logistic support vessels and pontoons/barges although the Lightweight Modular Multi-purpose Spanning Assembly (LMMSA) was tested in 1990 to interface ELCAS with a floating RORO discharge platform.
Lightweight Modular Causeway System (LMCS)
The LMCS was developed by the U.S. Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL) as a lightweight alternative to rigid modular pontoons. The flotation tubes are neoprene-coated heavyweight nylon and are inflated to 3 psi to support rigid deck panels. LMCS sections are connected using pre-tensioned cables and connectors in order to form a floating causeway.
Total weight is approximately 25 tonnes per 25m section and can be packed down into a number of ISO containers, two per 25m. It was intended to be carried aboard the Joint High-Speed Vessel but has also been adapted for wet gap crossing where it’s light weight, air portability and high load capacity (70 tonnes) is particularly valuable.
Even the USMC have taken an interest, using LMCS as a towed pontoon for moving light vehicles and stores to shore from a T-AKE ship, somewhat like a Mexeflote, and the air deployability of it is certainly attractive.
LMCS can support relatively heavy loads but is susceptible to deflection under wave loading which would severely limit offload rates with containers and tractor trailers.
Advanced Cargo Transfer Facility
Following the 1982 Falklands conflict, the US Department of Defense initiated a number of studies to investigate means of improving cargo transfer over a beach and after a number of years published a paper on a system called the Advanced Cargo Transfer Facility (ACTF)
ACTF proposed a system that comprised a 2,500-foot long pier using 16 jack-up foundation modules, eight mooring modules and two berthing modules. These could be assembled and used to transfer containers to the shore in sea state 4 from in-service container ships without the need for lighters. Jack-up platforms were used in combination with a purpose designed universal foundation system that could accommodate sand, clay, rock or coral seabed conditions.
Ships would be manoeuvred using winch barges secured to the seabed with propellant driven anchors.
Once in position, they would be offloaded from both sides onto a rail mounted trays that propelled them to the shore using linear induction motors. As can be seen from the diagram above, the facility did not have its own cranes but instead made use of the T-ACS crane ships, like the SS Cornhusker State
Two truss designs were described.
ACTF has a great deal to offer Requirement 3 because it proposed dispensing with lighters and providing a facility for large 35,000-tonne cargo ships to offload directly whilst anchored in 15m of water at up to Sea State 4.
The concept was developed further with improvements to the crane handling system but it was not taken into production.
Based on technology and systems developed for the North Sea oil industry, the Falkland Islands Intermediate Port and Storage System (FIPASS) was designed to resolve a number of issues; port access, refrigerated warehouse space and personnel accommodation. Six North Sea oil rig support barges (300×90 ft) were connected together and linked to the shore via a 600-foot causeway. Four of the barges carried warehouses, with provision for refrigerated storage. In addition, there were accommodation offices, which include a galley and messing facility for 200 persons.
The first cargo ship to use Flexiport unloaded 500 tonnes of general cargo and 60 ISO containers in 30 hours, by way of comparison, the same load, offloaded using Mexeflotes, took 21 days.
All this cost £23 million.
The company that designed FIPASS was ITM Offshore, realising the potential they developed the ‘Flexiport’ concept.
Much like ACTF, Flexiport has many relevant attributes for Requirement 3.
The MOSES Pier
The MOSES pier is one of the more recent proposals for the provision of a ship to shore causeway system.
The goal of MOSES project is to design a causeway that can reach large ships in deep water, keep vehicles dry, and be safely operational in at least Sea State 4.
This is obviously very close to Requirement 3.
MOSES is a result of work carried out by students on the National Research Enterprise Intern Program sponsored by the Office of Naval Research, as such, it is relatively limited in maturity but it does show a great deal of promise.
The MOSES pier consists of a large fabric filled structure that is pumped full of seawater. When pressurised it forms a roadway 1m above sea level that can carry heavy vehicles. The weight of the water in the fabric creates sufficient downward force to ensure stability in the surf zone.
Like ELCAS and LMCS, it makes the assumption that only landing craft and other lighters will dock at the pier head. It only caters for RORO vehicular traffic and has no cranes or other means of offloading vessels. It also assumes that the pier will be landed at a beach, no other terrain can be accommodated.
Visualise it as a long RORO linkspan.
One of the more ingenious aspects of the proposal is that positive water pressure is maintained in the structure by large open topped water reservoirs. This provides positive pressure for little energy expenditure and allows a ‘puncture reserve’ to be maintained. If the structure experiences a significant puncture the reservoir can provide enough time to maintain rigidity and thus allow safe evacuation of the pier. The cellular fabric construction is simply unspooled from a drum and filled using the reservoirs.
After a number of evolutions the final proposal described a 150m continuous structure with roadway planking to protect the fabric.
Further investigations examined the ship interface and concluded that the proposed deployment method would be sub optimal so one the original concepts of using a jackup barge was re-examined.
The jackup platform was called a Mobile Support Platform (MSP) and would be used both for deployment of the pier, and interfacing to landing craft and lighters.
Floating Container Port
Scapa Flow is synonymous with the Royal Navy but a research study conducted a few years ago looked at using it for the ‘greenest’ container port in the world. Instead of developing shore facilities the study looked at a number of floating concepts.
Scapa Flow, in the Orkney Islands could become the world’s greenest post if a clever plan that has been drawn up by researchers from Edinburgh Napier University’s Transport Research Institute (TRI) is adopted. The blueprint for the transhipment port could also could bring ‘substantial’ benefits to Scotland’s economy. The TRI estimate that the floating hub, which consists of a large storage vessel fitted with cranes, could nearly double the current £16bn value of Scotland’s exports of manufactured goods and that spin-off jobs would also be created for Scotland as the hub’s host nation.
Ultimately, the study was not taken forward for economic and other reasons but the research was sound.
At around £40m, the proposed floating port, called the Floating Container Storage and Transhipment Terminal or FCSTT, would cost approximately £80m less to build than a conventional land-based port offering similar capacity. What the proposed Scapa Flow Floating Container Storage and Transhipment Terminal system did was provide a floating transhipment capability, putting a storage and handling buffer in between vessels.
A couple of design concepts were considered, taking into account container vessel size, crane reach and other factors.
The first design concept considered a barge and travelling portal crane design.
The barge concept provided for the most flexibility using existing crane designs. It could easily transfer containers from a 13 container wide Panamax ship to either an 8 or 10-row feeder or lighter. If a wider barge were used it would provide greater storage capacity but given the limitations of existing cranes would not allow direct transfer from a 13-row container ship to one with 10 rows. In this context, this compromise might be acceptable.
The throughput of a twin barge, twin travelling gantry crane system would be based on a 20 hour operation time, be in the order of 740 crane moves. These moves either being directly from the main vessel to the feeder or from the main vessel to barge storage/barge storage to the feeder, or any combination in between.
The second design concept considered converting a surplus Panamax container ship and fitting it with 4 pedestal cranes instead of the travelling portal cranes on the barge.
The conversion would be self-deploying and offer a greater throughput than the barge option but would need larger cranes even to reach an 8 row feeder vessel and would be more costly in capital and operational terms.
Throughput was estimated at 1488 crane moves per 20 hour day.
Crane pendulation is caused by a combination of operator input, relative ship motion and system dynamics. Crane operations become impossible in Sea State 2 to 3 and above and this is compounded if both platforms are in motion, in ship to ship transfer for example.
The US Navy Seabasing programme has been looking at various solutions to the problem of crane pendulation including heave compensating cranes, the Auto log cable transfer systems and others.
The latest solution is the Large Vessel Interface Lift On Lift Off (LVI LO/LO) from Oceaneering.
LVI LO/LO tackles the challenge of two ships moving in 6 degrees of freedom in relation to each other, akin to threading a needles being carried by a horse, whilst riding another horse!
The objective of the study was to prove vessel to vessel container transfer in Sea State 4.
Trials were conducted using the AC5 SS Flickertail State.
It is an impressive feat of engineering, but excruciatingly slow
Self-powered barges are not the fastest of craft though, so it would be a trade-off between deployment speed and deployment ease. A good example of the type is the Damen Crane Barge 6324. It is equipped with self-contained accommodation for up to 12 personnel, basic navigation and propulsion options and a large Liebherr CBG 350 Transhipment Crane.
The CBG 350 can lift up to 45 tonnes at 36m outreach and when equipped with a container spreader, easily handle fully laden 40 foot ISO containers.
I describe the Mulberry Harbour in some detail at the link below;
Much of the fundamental work carried out by the designers of Mulberry is valid today.
Discussion on Existing Systems
Every single one of the systems described are both impressive, and extremely relevant to Requirement 3.
There is no doubt ELCAS-M is a marvellous piece of engineering that has no peer (no pun intended) in any armed force in NATO, or anywhere else for that matter. But, it has a number of issues that take the shine off and make it only partially suitable for Requirement 3.
Ship Interface; at 6m depth, it can only accommodate smaller vessels and lighters. Given one of the underlying requirements for Requirement 3 is to cut out the use of slow lighters and double handling, it needs to be approaching double that. The ELCAS crane cannot offload the LCU-2000 without the craft repositioning and the LSV at all. RORO cargo is not offloaded except by sling.
Bottom Conditions; because it can only use piles to support the pier deck bottom conditions have to be sand and clay. Requirement 3 has to be able to work in rocky conditions, concrete and other complex sea bed environments.
Build Sequence and Time; ELCAS-M requires the landing of the components before construction can start, this is time-consuming and is limited to a beach with plenty of space. It also requires a lot of MHE, personnel and construction equipment. ELCAS-M needs 7 marshalling areas for staging, storage, generators and others requirements. Because the modules are no larger than an ISO container they are strategically deployable, but require a great deal of handling in use. It is easy handle small Lego blocks, but it means a lot of handling.
Throughput; throughput is a difficult factor to quantify because there are so many variables, but a number of exercises have proven the stated design throughput to be very optimistic. Although both sides of the pier can be used and the pier is wide enough for two-way traffic the means of offloading containers is relatively slow, manually connecting slings and spreader bars to container twist locks. No automatic spreaders are used. High winds slow offload severely. As a whole system, the need for containers to be double handled (ship to lighter) decreases actual throughput significantly.
Sea State; when installed, ELCAS-M is very resistant to wind, wave and tide but building and operating are limited by sea state, current velocity and the wind. Manoeuvring lighters into position and crane pendulation make offload operations hazardous.
Skin to skin transfer, Mobile Landing platforms, automated cargo handling and heave compensated cranes are all there, but no pier. Of course, this is intentional, in the Seabasing concept, there is no requirement for ELCAS.
Lightweight Modular Causeway System
The use of inflatable pontoons for bridging and causeways has been a feature of US military bridging for many years, they have a great deal of experience. Whilst the floating nature of LCMS in use as a pier to shore would be valuable insomuch as it would be somewhat independent on bottom conditions, a floating pier creates many problems with waves and sea state. There are also questions on durability in an offshore environment.
Advanced Cargo Transfer Facility
The ACTF was actually a very interesting concept, perhaps ahead of its time. The combination of propellant driven anchors, expanding truss piers, winch barges and container shuttles made for a very effective system. The expanding supported truss system was particularly ingenious because by dispensing with a bridge deck, the volume and weight of material used for the pier to shore was dramatically reduced. But there lies a problem, it was only able to move containers and pallets, not vehicles or bulk liquids.
FIPASS revolutionised cargo handling after the Falklands conflict and the fact that it is still, is a testament to the concept. Flexiport have built on this to create a concept that is well suited to Requirement 3, but is at a scale that makes transport difficult and its semi-permanent nature is somewhat at odds with the general requirement.
The Moses Pier
The most interesting part of the Moses Pier concept is not actually the pier, but the use of jackup barges to provide the ship interface.
Floating Container Port
The floating container port concept idea of using surplus Panamax vessels is worth exploring, it could be a relatively cheap means of providing the pierhead. The use of multiple large cranes also increased throughput significantly.
Floating Cranes and Crane Barges
Crane pendulation might be a significant issue of the pier head floats, the technology might be useful. It is expensive and slow, however. Crane barges are in widespread use and relatively inexpensive but they require calm water.
Although Mulberry was hugely ambitious, and at a scale in excess of Requirement 3, its lack of cargo handling equipment and poor deployability makes it of limited direct interest. The concept of three basic components; pierhead, pier and shore connector, is exactly what is needed though.
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