Laying the communication cable: methods of installation in the ground, trench and pipes

Laying Communication Cables: A Complete Guide to Installation in Ground, Pipes, and Trenches

Laying communication cables is a critical stage in the construction and modernization of data transmission lines, telephone networks, and telemechanics systems. The reliability, durability, and quality of communication for many years depend on how correctly the installation method is chosen, regulatory depth requirements are observed, soil types and protection requirements are considered. Errors during installation can lead to cable damage, line breaks, difficulties during repairs, and consequently, costly restoration work.

In this guide, we will detail the main methods of laying communication line cables: in the ground (trenchless and trench methods), in pipes, cable ducts, and inside buildings. We will consider requirements for depth, protection, cable selection, and provide practical recommendations based on regulatory documents and professional experience.

1. Main Methods of Laying Communication Cables

The choice of a specific method is determined by the project, route conditions, cable type, economic feasibility, and operational reliability requirements. All methods can be divided into several main groups.

1.1. Laying Communication Cables in the Ground

This is the most common method for backbone and intra-zone communication lines, as well as for distribution networks outside populated areas. It provides good protection from external influences and stability of parameters.

• Laying communication cables in a trench:
  • The trench is excavated mechanically (excavator, bar cutter) or manually (in confined spaces, at intersections with other utilities).
  • Installation depth depends on the soil type, climatic zone, and line purpose. According to regulations, the minimum depth for laying communication cables in a trench is:
    • For cables in a plastic sheath (TPP, VP) — at least 0.7-0.8 m.
    • For cables in a metal sheath — at least 0.8-1.0 m.
    • When crossing arable land, ravines, or in rocky soils, the depth may increase.
  • Bedding: A bedding layer of sifted sand or soft soil, 10-15 cm thick, must be placed at the bottom of the trench.
  • Placement: The cable is laid on the bedding without tension, in a “snake” pattern, with slack to accommodate temperature deformations and soil movements.
  • Protection: From above, the cable is covered with a layer of sand (10-15 cm), then a layer of soft soil. For protection against mechanical damage and rodents, a warning tape or a layer of bricks (red, not silicate) is placed over the sand backfill.
  • Backfilling: Performed with clean soil (free of stones, construction debris, slag) with layer-by-layer compaction.
• Trenchless laying (using cable plows): Used on long sections of the route without intersections. A special cable plow cuts a narrow slit in the ground, simultaneously laying the cable at a specified depth. This method is highly productive but requires homogeneous soil and the absence of large stones.
• Types of cables for laying in the ground:
  • For direct burial in the ground, armored cables are used (e.g., with tape or wire armor, protected by a polyethylene hose). These can be TPPepBbShp communication cables (with hydrophobic filling and armor) or optical cables with steel wire armor.
  • Communication cable in a plastic sheath without armor (e.g., TPPep) is allowed to be laid in the ground only in protective pipes.

1.2. Laying Communication Cables in Pipes

Laying communication cables in pipes is one of the most reliable methods of protection against mechanical damage, aggressive soils, stray currents, and rodents. It also allows for future cable replacement or addition without opening the route.

• Types of pipes:
  • Polyethylene pipes (HDPE, LDPE): The most common. Lightweight, flexible, corrosion-resistant, have a low friction coefficient, which facilitates cable pulling. Supplied in coils or lengths, joined by welding or fittings.
  • Asbestos-cement pipes: Strong, non-combustible, but heavy and brittle. Require a concrete base. Used less frequently, mainly in cable ducts.
  • Steel pipes: Used in short sections with high mechanical loads (under railways, highways), as well as in fire-hazardous areas. Require anti-corrosion protection.
• Technology:
  • Pipes are laid in a trench on a prepared base (sand bed, concrete screed). The depth of pipe installation is at least 0.5-0.7 m to the top of the pipe.
  • Typically, one cable is pulled into one pipe. For multi-cable lines, a bundle of pipes (blocks) is used, which can be combined into concrete blocks or laid in one trench with intervals.
  • To facilitate cable pulling, special lubricants are used, and at route turns, inspection wells (cable wells) with a bending radius sufficient for pulling are installed.
  • After pulling the cable, the free space in the pipe may be sealed (with plugs, seals) to prevent moisture and rodent ingress.
• Application: This method is especially relevant for laying communication cables in the ground with a high groundwater level, in rocky soils, on the territories of industrial enterprises, at intersections with utilities, and for urban telephone networks (cable ducts). For internal installation in buildings, pipes (corrugated PVC, metal conduits) are also often used.

1.3. Laying in Cable Ducts, Collectors, and Tunnels

This method is widely used in cities and on the territories of industrial enterprises, where laying in the ground is difficult or impossible due to dense development and a large number of underground utilities.

• Cable duct: A system of underground pipes (channels) and inspection wells (telephone manholes) designed for the placement, installation, and maintenance of communication cables. Cables are pulled into free or partially occupied channels using winches and ropes. In occupied channels, laying new cables is only possible in protective polyethylene pipes.
• Collectors and tunnels: Underground structures of large cross-section, housing various utilities (heating networks, water supply, communication and power cables). Laying cables in collectors and tunnels is carried out on special brackets and consoles. This provides convenient access for inspection and repair. Rollers and winches are used for pulling cables. If the route length exceeds 1 km or the cable weight exceeds 3 kg/m, mechanized pulling is used.

1.4. Laying Communication Cables Inside Buildings

Inside buildings and structures, the installation of communication cables is carried out using exposed or concealed methods.

• Exposed installation:
  • In cable ducts (trunking) — an aesthetic method for offices, providing access to cables.
  • On trays — used in technical rooms, server rooms, attics, allows laying bundles of cables.
  • On walls and ceilings using staples or clips — a simple method for non-critical lines.
  • In corrugated pipes (PVC, metal conduits) — for additional protection.
• Concealed installation:
  • In wall chases (grooves) followed by plastering.
  • In voids of building structures (behind suspended ceilings, in raised floors).
  • In floor screeds (in pipes).
• Applied cables: For internal installation, UTP communication cables (unshielded twisted pair) and F/UTP (foiled twisted pair) of categories 5e, 6, 6A and higher are widely used. They are designed for structured cabling systems (SCS) and provide high-speed data transmission. For telephone lines inside buildings, TPP cable in PVC sheath may also be used.

1.5. Laying on Bridges and Across Water Barriers

• On bridges: The cable is laid under the pedestrian part or in special channels, in pipes (asbestos-cement, steel, plastic) with protection against vibration and mechanical damage. Insulation of the cable from metal bridge elements and grounding of the bridge are required.
• Across water barriers: Performed by laying the cable in a trench on the bottom of the reservoir (manually or mechanically from floating craft) or via bridge crossings. Special cables in reinforced hermetic sheaths (with hydrophobic filling, with aluminum or lead sheath, armored) are used.

2. Regulatory Requirements and Laying Rules

The rules for performing work are regulated by a number of regulatory documents, including building codes and regulations (SNiP), departmental building codes (VSN), operational technical regulations (PTE), and GOST standards.

• Project documentation: Any laying of communication cables must be carried out strictly according to the project, agreed upon with interested organizations (owners of adjacent utilities, road services, etc.).
• Route preparation: Before starting work, the route must be cleared of shrubs, boulders, and construction debris. In wooded areas, a clearing is made.
• Protective zone: A protective zone is established along the underground cable route (usually 2-3 meters on each side), within which excavation work is prohibited without agreement with the line owner.
• Intersections with other utilities: When crossing power cables, pipelines, roads, minimum distances must be observed and protective measures applied (laying in pipes, installing warning tape).
• Temperature conditions: Laying cables at low temperatures (usually below -10°C…-15°C) requires pre-heating the cable or using special technologies.
• Bending radius: The minimum allowable bending radius of the cable must be observed (usually not less than 10-15 outer diameters for non-armored and 15-20 for armored cables).
• As-built documentation: Upon completion of work, as-built drawings (profiles) are prepared, recording the actual position of the cable (depth, references to landmarks, intersection points, couplings).

3. Choosing a Communication Cable Depending on the Laying Method

4. Main Errors When Laying Communication Cables

• Insufficient trench depth: Can lead to cable damage during excavation work, freezing, exposure to surface loads.
• Lack of sand bedding: Sharp stones and hard lumps of soil can damage the cable sheath.
• Cable tension: Laying without slack (“tight”) creates mechanical stresses that, during temperature fluctuations or soil movements, can lead to conductor breakage or the formation of “loops” (geometry violation).
• Bending radius violation: Sharp bends, especially at entry points into wells and buildings, lead to insulation damage and compromise the integrity of the screen or armor.
• Sheath damage when pulling into pipes: Using insufficient lubricant, presence of sharp edges on pipes or in wells.
• Ignoring protection requirements: Lack of warning tape or bricks above the cable in the trench increases the risk of damage during excavations.
• Incorrect cable selection: Using a non-armored cable for laying in the ground or a cable with a PVC sheath for outdoor installation (destruction under UV radiation).

5. Conclusion

Competent laying of communication cables is a complex task requiring consideration of many factors: from choosing the optimal installation method (in the ground, trench, pipes, or inside buildings) to strict adherence to depth regulations, protection, and work technology. Only such an approach guarantees reliable and long-term operation of communication lines, whether it is a backbone fiber optic cable or a “last mile” distribution network.

A key success factor is also the use of high-quality, certified materials. The range of cable and wire products from JSC “Kazenergokabel” includes a full spectrum of solutions for any installation method: communication cables of the TPPep grade for telephone networks, UTP/FTP cables for structured cabling systems, VP wires for special applications, as well as optical cables in various designs. All products are manufactured according to GOST and are accompanied by the necessary documentation, guaranteeing the reliability and durability of your communication lines.