Tunnel Backfill

The material "backfill cellular concrete" is composed of neat cement grout and a preformed foaming agent. Backfilling is the process of filling voids that occur during tunnel and shaft excavations and lining processes. Voids that exist between the excavated tunnel and initial support and the final liner, and the annulus outside pre-formed liners must all be backfilled.

Geo-Cell Solutions, Inc. has successfully used Geofoam SNP™ and Geofoam SP™ cellular concrete to backfill projects with variable densities. These densities are based on the geology of the surrounding ground and the structural and operational requirements of the project.

Backfilling with Geofoam cellular concrete will ensure that the pipe stays on line and grade remains centralized within the excavated tunnel opening. Using Geofoam SNP Cellular Concrete provides additional protection for the pipe from shifting, water infiltration, and corrosion as well as uniform load transfer from the ground to the pipe and from the pipe to the ground. Geofoam SNP used in active fault crossings allows the ground around the pipe to move without shearing the pipeline. Geo-Cell Solutions has specialized equipment that synchronizes batching, mixing and placement, key ingredients to a proper installation.

Reasons for using Geofoam SNP:

  • Stabilizes the liner during construction
  • Secures lining systems
  • Full contact with the surrounding ground and liner
  • Permeability of the final liner system
  • Reduces ground water flow around the final liner
  • Added corrosion protection
  • Surface settlement above tunnels and around shafts
  • Reduces rock deformation around the tunnel

Advantages of Geofoam cellular concrete over normal weight backfills:

  • Lower unit costs
  • Greater pumpability
  • Greater flowability
  • Variable density
  • Compressibility
  • Speed of placement