This book provides comprehensive guidelines for the filling of voids for both soft ground and rock tunnels and shafts. The underground construction industry will find these guidelines useful for minimizing misunderstandings related to backfilling and contact grouting terms and methods; improving the quality of contract documents related to backfilling and contact grouting and the in-place material; reducing costs and schedule time; and avoiding or minimizing potential claims. The coverage includes: Geological Conditions; Structural and Operational Requirements on the Completed Facility; Backfilling and Contact Grouting for various types of Ground Support and Lining; Grout Material; Grout Properties; Backfilling; Backfilling Methods; Backfill Mix Designs; Contact Grouting; Equipment; Record Keeping; Quality Control; and Contract Documents. These guidelines were prepared by the AUA Technical Committee on Backfilling and Contact Grouting of Tunnels and Shafts. The committee includes a wide range of experts representing engineering firms, contactors, equipment and material suppliers, and consultants.