Progress of the JIH Cable Project
|1998-003||January 22, 1998|
On January 28, before the main phase of the JIH cable laying work begins, KDD will commission a new cable ship, KDD Pacific Link. Besides the JIH cable laying work, KDD Pacific Link, along with KDD Ocean Link now in service, will be assigned to the maintenance of optical-fiber submarine cables and the construction of new cables in Southeast Asia and the Pacific region.
In the JIH cable construction, KDD became the first Japanese telecommunications carrier to use horizontal drilling technique for building a conduit in a coastal area. KDD adopted the technique to reduce the time and cost of constructing JIH cable conduits in coastal areas.
(1) Commissioning of KDD Pacific Link
Kokusai Cableship Co., Ltd., a subsidiary of KDD, procured KDD Pacific Link in November 1996. The ship has been modified in Britain and Japan, where it has been fitted with the equipment necessary for laying and maintenance of cables. KDD will officially name the ship and launch it on January 28.
KDD Pacific Link is 109 m in overall length and 7,764 tons in gross tonnage, and has accommodations for a crew of 58. The ship features such high-performance ship control equipment and cable handling equipment as Dynamic Positioning System and a computer-controlled cable engine for paying out the submarine cable. The ship can hold approximately 4,500 km of cable at a time and engage in cable laying work for 50 consecutive days.
After the crew undergoes work training and the cable is loaded on the ship, KDD Pacific Link will set sail for an area off the coast of Sendai from mid-May to lay the Pacific side route cable, the total of some 2,300 km of the JIH cable extending from Ibaraki to Chikura, Ninomiya, Toyohashi, Shima, Kochi, and Miyazaki.
KDD plans to use KDD Pacific Link and KDD Ocean Link, which is currently used for maintenance of international cables, to contribute to the construction and maintenance of large-capacity, international submarine cable systems in the Asia-Pacific region.
(2) Implementation of horizontal directional drilling technique
KDD became the first Japanese telecommunications carrier to use horizontal directional drilling technique for building a cable conduit in a coastal area. KDD adopted the technique for constructing conduits to be laid underground between the coastal sections of the JIH cable and submarine cable landing stations. So far, KDD has used the technique in Matto, Akita, Niigata, and Toyohashi.
In constructing a conduit for telecommunications circuits, the common practice is to cut and cover the ground or to drill a passage for the conduit using a boring machine lowered into a pit, without cutting and covering.
With the horizontal directional drilling technique, a special boring machine is fitted with a drill pipe. The drill pipe is inserted into the ground and the boring machine, working from the ground surface, drills through the ground towards the ground surface on the destination side as it draws a curve. The drill pipe is then run in reverse to draw the cable conduit into the ground and complete the burial work.
With KDD's boring machine, it is possible to construct a conduit of up to 200 m. As it requires no pits or cut and cover required by the conventional technique, it can substantially reduce both construction cost and time.
KDD plans also to use the technique in Sendai.
(3) Landing and laying of JIH cable
Cable work can generally be classified into landing work (from some ten kilometers off the landing coast to the coastal area) and laying work (in the ocean). The two types of cable works will be advanced concurrently for the JIH cable.
JIH cable's landing work has been conducted at KDD's existing submarine cable landing stations in Ninomiya, Miyazaki, and Okinawa ahead of the ocean cable laying work. KDD will begin landing cables to new submarine cable landing stations for the JIH cable, beginning with Toyohashi Station (Aichi Prefecture) on February 20.
Five cable ships, including KDD Pacific Link, will be used to simultaneously lay the JIH cable's loops and branches both on the Pacific and Sea of Japan sides. KDD expects to complete all of the landing work by early July and all of the laying work by mid-November this year.
Profile of KDD Pacific Link
|1. Owner:||KCS Panama (Panamanian subsidiary of Kokusai Cableship Co., Ltd., a KDD subsidiary)|
|4. Overall length:||109.0 m|
|5. Breadth:||20.50 m|
|6. Gross tonnage:||7,764 tons|
|7. Cable tank capacity:||4,000 tons, or approx. 4,500 km|
|8. Service speed:||12 knots (approx. 22 km/h)|
|9. Continuous service days:||50|
Conceptual Diagram of Horizontal Drilling Technique
1. Conventional technique
When constructing a conduit for telecommunications circuits, the common practice is to cut and cover the ground. When a river or buried structure, for example, prohibits the cut and cover technique, another method, called microtunnelling, has been used to construct the cable conduit. The microtunnelling requires a tunnel boring machine to be lowered into the ground to the depth of the conduit. This makes it necessary to excavate a pit on either end of the conduit beforehand.
2. Horizontal drilling technique
With the horizontal directional drilling technique, a drill pipe installed on the tip of a special boring machine is inserted into the ground. The boring machine sprays muddy water as it drills through the ground underneath the obstacle towards the ground surface on the destination side as it draws a curve. When the boring machine comes out of the ground on the destination side, the cable conduit is connected to the tip of the drill pipe. The drill pipe is run in reverse back to the starting side to draw the cable conduit into the ground and complete the burial work.