1. The cross-sectional dimensions of the trench should comply with the construction drawing requirements. The bottom width varies with the number of optical cables. Generally, for 1 to 2 optical cables, the bottom width is 30-1000cm; for 3 optical cables, the bottom width is 1375cm; and for 4 optical cables, the bottom width is 1625cm. The top width of the trench is approximately the bottom width + 0.1 times the burial depth. Optical cables laid in the same trench must not cross or overlap. The straightest possible optical cable trench should be constructed on two straight lines. Obstacles can be bypassed on a straight line, but after bypassing the obstacle, the cable must return to the original straight line. The bending radius of the bend should be no less than 20m. When laying optical cables on slopes with a gradient greater than 20 degrees and a length greater than 330m, an S-shaped layout or other treatment measures as required by the design should be adopted.
2. Trench Bottom Preparation: In general areas, the trench bottom should be filled with fine soil or sand and gravel, then compacted to a thickness of approximately 250cm. Areas with weathered rock and gravel should first be covered with approximately 125cm of mortar, followed by fine stone or sand and gravel to protect the optical cable from the sharp edges of the gravel. Mortar may not be required if the cable is sheathed with steel wire armor. In areas with soft soil prone to collapse, wooden stakes and blocks can be used as temporary retaining walls for protection.
3. Direct burial cable laying is mostly carried out in the field. Mechanical laying is only possible if the route is along a highway. Mechanical laying uses a truck or a reel-and-reel truck for traction. A crane or forklift first loads the cable reel onto the vehicle and winds it around the frame. The small cutting plate or metal reel cover on the reel is removed. The supervisor should verify that all preparations are complete before commencing cable laying. The motor vehicle should move forward slowly, while the optical cable is manually pulled out of the cable drum and gently placed on the edge of the trench. After it is released for 20m, it is manually lowered into the trench. At present, the conditions for direct burial laying using mechanical traction are often rare, and manual laying is generally done. There are two ways of manual laying: one is the straight-line shoulder-carrying method (note that no matter what method is used, the optical cable is not allowed to be dragged on the ground). The personnel are closely spaced and the command personnel act in a unified manner; the other is the manual lifting method. First, the optical cable is reeled into an 8-shape, and 10 8-shapes are piled for every 2km of optical cable. Each group is tied with 6 groups with leather wire. Each group is carried by 4 people, and each group is assigned one person to coordinate. The first group is guided by 2 people in front. When laying, each group lifts and moves forward along the trench under unified command.