Deadman Anchor-heavy

Rear Target Detail

Rear Target Detail

Front Target Detail

Planned route to vault

Cable layer

Plan View

Figure 6.1

Range pole configuration for cable landing.

Global Positioning System (GPS) and Differential GPS are currendy in wide use. Other navigation-survey systems such as Super Hydro and the Diver Navigation System (DNS) are also used for cable route surveys. More information on navigation systems can be found in Section 4.4.

6.2.1.2 Trenching, Rock, and Berm Removal. During the planning stages a study should be made of the beach area and the effects of winds and waves. The information from this study will be used to determine the requirements for burying the surf and shore sections to provide protection from weather, surface, and local traffic conditions. Generally, cables are brought through the surf zone, beach, and dunes to the inshore termination point. The cable landing area should be selected so that ecological damage is minimized and restoration can be effectively carried out. Environmental permits will be required (see Section 1.4.4).

Berm removal comprises cutting a 50-foot swath through the berm and dunes with a bulldozer to provide ample room for pulling cables to the vault. The cutaway material should be stowed in a convenient area for later replacement.

Cable trenching onshore and in the surf zone can be done with a backhoe. Material that is not easily excavated with a backhoe may require the use of controlled blasting excavation, as discussed in Section 2.7, or other suitable mechanical trenching techniques. The trenches are cut to a minimum depth of 4 feet. The actual depth of protective burial of the cable depends on the changing nature of the beach area and local traffic; high erosion rates or ice scour will require deeper burial. The trench width is determined by the number of cables, the required separation, and the need for a cable protection system.

6.2.1.3 Cable Stowage. The handling and stowage problems encountered are related to the physical characteristics of the cable, such as diameter, weight, minimum bending radius, and torsional stiffness. Many cables have a preferred coiling direction. When coiled in the wrong direction, the cable becomes stiff and will not lay flat in the pan. Some cables are torque balanced and are stiff in either direction. They must be handled carefully and coiled in much larger diameter loops.

Stowage of cables on wood or steel reels poses a number of cable-laying problems if the total length of cable to be laid exceeds that which can be stored on a single reel. For longer lengths it is necessary to splice the cable on the bitter end of one reel to the leading end of the next at sea. This method is dependent on the availability of an experienced splicer and splicing equipment.

On cable ships it is customary to carry long lengths of cable in cable tanks. These tanks are specially designed to allow for storage of the cable in concentric circles with dense packing, to get the maximum cable possible into the tank.

Another stowage technique uses portable cable pans set on the decks of barges. Normally the cable pans are loaded at the cable factory and shipped by rail or water to the site. A large crane is required to load the cable pan onto the cable barge. This technique allows cable loading and splicing operations to be performed in port.

As a minimum, electrical continuity checks should be made at the following steps in the loading process:

• Prior to splicing and prior to unreeling

• After each splice is made

• After unreeling each reel and stowing aboard prior to making the next splice

In some cases it may be necessary for UCT personnel to load the cable from reels onto the cable barge. In this case a cable pan can be fabricated using lumber and plywood to cover the available deck space. The dimensions of the pan will depend on the length of cable. A powered cable reel should be used for the shore portion of the cable. The cable is fed over guide sheaves to the center of the cable pan. A crane can be used to hold this sheave in location. The arrangement is shown in Figure 6-2.

As the cable is being transferred from a reel to a cable pan, one complete turn is applied on the cable for each loop in the pan. Therefore, care must be taken to ensure that the cable is sufficiently soft to accept twist and that the cable pan is sufficiendy large to reduce the amount of twist in the cable. Otherwise, the cable will form hackles and kinks and the cable transfer cannot be accomplished. The cable is guided by hand to circles in the cable pan. Dunnage is placed over each layer of cable to minimize nicking of the cable between lower layers.

Chain Claw
Figure 6-2. Arrangement for loading cables on a barge from storage reel.

6.2.1.4 Hauling the Cable Ashore. A very important part of the cable installation operation is bringing the cable ashore from the ship or barge to the cable vault. During this stage of the operation, the cable could be easily damaged by bottom obstructions or excessive hauling forces. One procedure is as follows:

• Using a small inflatable or amphibious vehicle, a hauling line is passed ashore from the cable ship.

• The seaward end of the hauling line is attached to the cable using an in-line swivel and shackles. The swivel allows the cable to rotate freely and release rotational torque, which would be built up from removal of the cable from the storage bins.

• With a strain on the hauling line from shore, the cable is pulled off the cable ship and floated off the bottom using float balloons tied 15 to 20 feet apart on the cable.

• The float balloons are removed after the cable is hauled ashore and secured to the cable vault or deadman anchor.

The cable float balloons reduce the required hauling force and keep the cable from snagging on seafloor obstructions. It is very important to ensure that the cable float balloons (usually called pumpkin floats) are se-

cured using the proper harness arrangement and knots. "D" rings on these floats are NOT designed to carry the load. The correct arrangement is shown in Figure 6-3.

Deadman Anchors

Figure 6-3. Harness arrangement and knots to secure float balloons.

specified trench line, to avoid obstacles, or to allow the hauling vehicle to operate on paved surfaces. The turn can be accomplished using a beach sheave or roller assembly, as illustrated in Figure 6-5. The sheave diameter must be selected to be compatible with the minimum bend diameter of the cable. Care must be exercised to ensure that the beach sheaves are properly rigged and that the deadman anchors are designed to carry the expected hauling loads.

Sometimes the deadman anchor is formed in place by pouring fresh concrete. In this situation, it is important for the concrete to reach a

Figure 6-3. Harness arrangement and knots to secure float balloons.

Figure 6-4 shows a typical arrangement for shore landing of a cable. In this case a winch is used for the hauling operation. The hauling force that brings the cable ashore must also be provided by bulldozers, backhoes, tractors, and other heavy machinery. At least two hauling vehicles are required since there is usually not enough room to pull the cable from the ship to the vault in a single pull. When wheeled (not tracked) vehicles are used to provide the hauling force on sandy beaches, traction can be increased by using available roads, runways, and other paved areas.

Directional changes in the hauling route are often necessary to follow a

Cable

20k winch

<x termination J building j?

Open trench

Backhoe or deadman anchor

Cable

20k winch

Roadworks Trench Cable

Open trench

Shoreline

15 ft min

1 in. poly hauling with in-line swivel

Cable with float balloons

Turning sheave and beach anchor location

Shoreline

15 ft min

1 in. poly hauling with in-line swivel

Cable with float balloons

Sea bouy

Sea bouy

Deadman Construction

Cable vessel

Figure 6-4. Arrangement for hauling cable ashore using a winch.

full strength cure before pulling operations begin. Full strength may require 48 to 72 hours depending on environmental conditions.

The hauling operation is particularly important. From the time the cable leaves the ship, the beach crew must maintain positive control to ensure that die floating cable is straight and that the end of the cable is not, accidently or otherwise, released. If heavy currents or wind forces are present, the floating cable can be assisted into position using small craft with tag lines to the cable.

Any time the cable is not attached to a hauling vehicle and the cable is floating, it is essential that the cable be tied off to a deadman anchor using stoppers. A deadman anchor should also be used when the load is being transferred from one hauling vehicle to another. Again it is important to be sure that the deadman anchor is designed to carry the expected loads of the cable or hauling system.

When sufficient length of shore cable has been pulled in, it should be tied off to a deadman anchor. It should not be released from this anchor until the float balloons have been removed from the cable, and the cable is resting on the ocean bottom.

6.2.1.5 Laying Inshore Cable from a Cable Ship. The most efficient way to lay the inshore portion of an undersea cable is from the cable ship. The seaward end of the cable is first deployed and the ship arrives at the transition point for the inshore cable. A line is passed ashore using a small boat secured to a winch or a beach-based vehicle, and the cable end hauled in to the onshore termination point. Float balloons are attached to the cable to keep it off the bottom while it is being pulled ashore. Although the technique is effective, it does pose a number of problems, as follows:

• The shore party and equipment must be available and ready to start landing operations when the cable ship arrives at the inshore cable deployment position.

Deadman anchor-^

Cable trench A

Deadman anchor-^

Cable trench A

Deadman Anchor

Note: Eye on sheave used for transporting only.

j— Bottom of trench

Concrete anchor—-"Hi Shackles

Section A-A

r- Concrete anchor Shackles r- JlUtUCS .

Note: Eye on sheave used for transporting only.

Figure 6-5 Beach hauling equipment.

• Either the length of inshore cable required must be precisely predetermined or the deep-sea cable will have to be cut and spliced to the inshore cable after the inshore cable ship has landed.

• The cable ship will be required to enter into a fixed mooring or to dynamically position itself at the offshore location for as long as it takes to complete the landing and splicing operation.

• Buoying off cable ends and other contingency planning to redeploy the cable ship must be made to provide for weather conditions that would adversely affect any part of the cable landing operation.

When the inshore cable is installed first, the ship is moored offshore of the cable landing site. The inshore cable is then hauled ashore as discussed above. When the inshore cable has reached the prescribed termination point, a wire stopper is attached to the cable and secured to a deadman anchor. The cable ship then breaks the moor and proceeds out to sea, laying the seaward cable.

6.2.1.6 Laying Inshore Cable from a Barge. This method involves loading the inshore cable aboard a barge, mooring the barge out beyond the surf zone, connecting the cable to a hauling device onshore with an inhaul line, and pulling the end of the cable to the terminal point onshore. The procedures for hauling the cable are the same as with the cable ship installation.

In addition to the towing vessels, inshore cable installation from a barge requires the services of small craft to carry hauling lines between the cable barge and the shore. The amphibians LARC V and LARC XV, as illustrated in Figure 6-6, are particularly useful, because not only can they carry the end of the hauling line ashore, but they can also move up the beach to assist in cable landing.

After the shore cable has been landed, the moor is broken ami the barge is towed out to sea while laying the remainder of the cable. A puller-tensioner winch (illustrated in Figure 6-7) maintains a fixed tension on the cable being paid out. Over the center of the cable pan a sheave is hung from a cable-stayed steel frame or other support that spans the open space. During the laying operation the cable passes from the stowage area, up and over the suspended sheave, through the puller-tensioner device, over the stern, through cable guides, and into the water. An example of the on-deck cable arrangement is shown in Figure 6-8.

6.2.1.7 Beach Area Restoration. After the cable-laying operation has been completed, restore die beach and surrounding area to its preinstallation condition. This must be done to minimize the environmental impact of the cable installation. Excavated material set aside during preinstallation operations should be returned to its original location. Landscaped areas should be restored, as should all affected roads, walls, and fences.

6.2.2 Protection and Stabilization

A detailed discussion on cable protection and stabilization systems is contained in FPO-1-78(3), Design and Installation of Nearshore Ocean Cable Protection Systems. The reader is encouraged to use this report for the full design philosophy. The information below is summarized from that report.

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