HDD machine diameter reduction: the soft soil layer is expanded, and the diameter of the hole is prone to shrinkage. After the drill pipe is removed, the water in the hole pours out from the drill pipe, indicating that the diameter of the hole is severely reduced. When the diameter is severely reduced, the laid pipe will be squeezed and deformed, or even stuck. In case of severe diameter reduction, use solid mud to protect the wall to balance the pressure in the hole and maintain the hole. Or increase the first-level drill bit to expand the hole, then clear the hole and lay the pipe. Choose PE and PVC pipes with high hardness and strong resistance to lateral pressure. If the diameter is slightly reduced, the pipe can be laid by cleaning one more hole.

Hole collapse: Reaming of sandy clay layer, sand layer, loose backfill soil layer is easy to collapse hole, collapse hole buried drill, stuck drill, stuck pipe laying, and caused road cracks to sink. Use solid phase mud and heavy colloidal solid phase mud for wall protection, which can effectively prevent hole collapse. If the hole collapses at the pile of rocks, the hole can only be enlarged after the rocks are removed.