As we lay the cable under the river

Hi, Habr. Probably many of you have seen our previous article about construction of the base station with tower on the roof. And today we want to talk about something else as the work that we recently had a chance to hold. It's about the conquest of two elements - the earth, and partly of water. Or rather, how we laid under the river fiber optic cable over a length of 980 meters.

Was a task - to connect an additional Fibre Channel Vladimir and Nizhny Novgorod region, Nizhny Novgorod on a line-Moore. The problem was that in this place, in an absurd accident, a river Oka. The width of the bed is decent, the depth is 6 meters.

Well, we are no strangers to hardship. It was decided to lay fiber optic cable under the surface of the river bottom. Since it is a regular cable for underground / underwater placement and not a special reinforced, it was necessary to protect it from external influences. The fact that the bottom ground rather movable, under the action of the bias currents are constant bottom surface mass. And if the cable is not protected, then sooner or later it will tear. For the same reason, can not be laid directly on the floor, it is also fraught with mechanical injuries.

Site Selection h4> Therefore, this solution is applied: at a depth of several meters below the surface of the bottom is laid steel sealed tube through which extends a cable from one bank to another. However, the ground for the section may be heterogeneous in composition, primarily on the density. There may be so dense rocks that lay pipe through them impractical or impossible. And not to be faced with similar obstacles, conduct reconnaissance on the supposed site of the bottom liner. During the week, with the help of divers was examined bottom relief, made of engineering-geological surveys. As a result of these studies and was selected for the construction of a specific area. Although I must say that even this measure does not guarantee successful laying the first time. But we were lucky, the river does not have a surprise and managed to lay a pipe with the first call.

Seal h4> To place the start of work on the bank paved trench for cable, a depth of about 1 to 5 meters.

At a distance of about 70 meters from the water's edge to drill horizontal directional drilling FORWARD RX44x160.

With this setting was first drilled input channel, and then it gradually began to dent, push right through the ground steel pipe with a diameter of 110 mm and a wall thickness of 8 mm. It is in it then will be laid fiber optic cable.

The pipe sections previously joined to each other at the thread and seam sealed to ensure tightness.

That's why it is so important that the soil of the river bottom was relatively low density. After the rig of tractive effort at 44 tons, it is necessary to push through the soil is pretty thin tube length of almost 1 km! And if in the path of the pipe will fall sufficiently tight, the tube can break, collapse, or step aside. And in such cases it is necessary to look for a new site and start all over again.

While the drill rig pushes the pipe under the river, on the other side, in the place to come to the surface was dug volumetric pit. A week after the start of laying pipe successfully emerged from the pit wall.

blowing cable h4> The most difficult step behind. Now the cable must be passed through a narrow, sealed tube kilometer length. Of course, it is not possible simply to push the. Instead, the end of the cable is attached to a small "pyzhu" which is inserted into the tube. After that, by setting the start-up of the fiber optic cable - injector PSI.1 - air is blown into the tube.

Source is the compressor:

Air pressure - 10 MPa - "wad" started to move through the tube and pull the cable. That is why the pipe must be sealed, otherwise through it just does not get to blow the cable. A few hours later, "wad" went well, the other bank. The cable will stretch under the river!

Conclusion h4> The total duration of the work, including the benthic survey was less than two weeks. This site link was the longest of us laid under the bottom of the river. Thanks to him, managed to close the ring fiber backbone with a total length of over 750 km, increase the capacity of "MegaFon" in the two regions.

Source: habrahabr.ru/company/megafon/blog/235347/