Welded wire fabric may be used in conjunction with shotcrete to rehabilitate deteriorated portions of either metal or concrete culverts. The welded wire should be anchored to the in-place pipe either through the use of drilled dowels, if the pipe is concrete, or by welding to either the corrugations (of metal pipe) or to previously welded studs. The shotcrete can then be placed by the use of high-pressure hoses. The repair can be designed to restore structural integrity, with little loss of hydraulic capacity.
Regardless of the method of repair or rehabilitation chosen, the possible need for grouting potential voids in the soil envelope surrounding the pipe should be addressed. Portland cement grout may be pressure-injected from the interior of the culvert through drilled holes located toward the bottom of the suspected voids. Drilled holes located toward the top of the pipe then allow for the trapped air and water to exit prior to the grout. Grouting of the voids is necessary to complete the structural rehabilitation of the culvert and to reduce the possibility of any future piping of the culvert backfill.
Where conventional grouting will fill the large voids adjacent to the culvert created by infiltration or piping, compaction grouting will densify the soil. The equipment, method of injection, and makeup of the grout will all be different from what is required for conventional grouting. Compaction grouting in addition to or in lieu of conventional grouting may be necessary. However, the benefit of knowing that there is a well-compacted, stabilized soil in the vicinity of the culvert may not outweigh the expense involved in the process of compaction grouting.
