I. Backfilling Techniques for Cable Projects

　　Process Standards:

　　(1) After placing warning signs on the cover plate to prevent external damage, backfill the area around the cable with compacted soil, or as required by the municipal authorities.

　　(2) Backfill soil for cable works shall be compacted in layers. In general, the compaction coefficient of the backfill soil shall not be less than 0.94, and the backfill soil shall be free of stones or other hard materials.

　　Key construction points for cable engineering:

　　(1) For directly buried cable installations, a layer of soft soil (free of stones or other hard foreign objects) or sand with a thickness of not less than 100 mm shall be laid on the upper and lower surfaces of the cable, followed by the installation of protective plates. The coverage width on each side of the cable shall exceed 50 mm.

　　(2) To prevent cable damage from external forces, a plastic warning tape shall be laid over the cable protection cover plates in cable engineering projects.

　　(3) At intervals of 50–100 m along straight sections, at cable joints, at bends, and at points where cables enter buildings, conspicuous orientation markers or marker stakes shall be installed.

　　II. Cable Duct Laying Works for Cable Engineering

　　1. Cable laying in conduit

　　Process Standards:

　　(1) Single-core AC cables shall be made of non-magnetic materials and comply with environmental protection requirements.

　　(2) The inner diameter D (in mm) of the drainage pipes selected for cable trench drainage shall not be less than 1.5 times the cable’s outer diameter (in mm), and shall not be less than 150 mm. Furthermore, the inner diameter of any given pipe section should not exceed two different values.

　　(3) During cable laying, the tensile force, lateral pressure, and bending radius of the cables shall be kept within the permissible limits in accordance with the requirements of each specific cable type.

　　(4) Protective measures shall be implemented at cable pulling heads, cable reels, traction vehicles, crossings, bends, and any other locations where cable damage may occur.

　　(5) When laying 110 kV and higher cables in cable projects, the lateral pressure at bends shall comply with the manufacturer’s specifications; if no specific requirements are provided, it shall not exceed 3 kN/m.

　　Key construction points for cable engineering:

　　(1) After pipeline installation is completed but before cable laying, each opening of the pipeline used for cable laying shall be dredged in two directions using dredging tools of the appropriate specifications.

　　(2) Remove nails and debris from the inner wall of the conduit to prevent damage to the cable during installation.

　　(3) If any doubts arise during dredging inspections, a pipeline endoscope shall be used for inspection, and the pipeline may only be put into service after such doubts have been eliminated.

　　(4) Prior to cable laying, cable payout racks shall be installed at the cable reel, wellhead, and corners of the shaft; the cable reel, traction vehicle, crawler conveyor, and rollers shall be positioned appropriately. The cable reel shall be equipped with a braking device.

　　(5) Cables shall be equipped with pulling heads. Otherwise, pulling heads shall be fabricated and anti-torsion devices installed prior to laying. Protective measures shall be implemented at cable pulling heads, cable reels, towing vehicles, bends, and any other locations where cable damage may occur. Dedicated personnel shall be assigned to supervise the operation and ensure unimpeded communication.

　　(6) After cable laying is completed, secure the cables to the cable supports within the shaft in accordance with the design requirements, and seal the conduit openings.

　　(7) Prior to cable entry into the conduit assembly within the cable work well, a neutral lubricant shall be applied to the cable surface.

　　(8) During cable laying, a nozzle-protection flared guard shall be installed at the cable outlet to protect the cable.