5.2　Backfilling

5.2.1　Backfilling pole holes，stay wire pits and bracing pole hole shall be compacted layer by layer，and compaction shall be made for each 300mm backfilling.The backfilling on downtown sideways shall be 50mm-100mm above the original ground surface；on other downtown grounds，the backfilling shall align with the original ground surface.In suburbs and fields，the backfilling shall be 100mm-150mm above the ground.

5.2.2　When backfilling cable trenches and silicon-core pipe trenches，fine soil shall be put in first，then the original earth.It is strictly prohibited to put stones，bricks，and frozen earth into trenches.The backfilling within 300mm of the top of silicon-core plastic pipe as well as those close to both sides of the pipe shall not contain gravels，broken bricks and other hard objects with diameter greater than 50mm.

5.2.3　For trenches of optical（electrical）cables and silicon-core plastic pipes buried in urban areas or suburbs，the backfilling shall be compacted each time when the thickness reaches around 300mm.On roadways or brick sidewalks，the backfilling shall level with road surface，and backfilling shall not sink before the road surface is repaired.

5.2.4　For trenches of optical（electrical）cables and silicon-core plastic pipes buried in field，the soil excavated shall be all filled back.The surface of backfilled trenches can be 50mm-100mm above dirt roads or 150mm above suburb ground.

5.2.5　According to design requirements，backfilling thickness shall be in accordance with the design requirements so as to properly cover man（hand）hole pits of silicon-core plastic pipes.And the other requirements for man（hand）hole pit backfilling shall comply with the current national standard Code of Construction and Acceptance for Communication Conduit Engineering GB 50374.

5.2.6　Design documents shall prevail，shall there be special requirements for backfilling in design documents.