Development and Testing of Insulating Shotcrete for the Application in Underground Tunnels

• Author / Creator

  Liu, Wei Victor

• The trapped geothermal heat in the infinite rock mass through which mine tunnels are excavated is a great threat to the safety of personnel and mine operating equipment in deep underground hot mines. In order to lessen the temperature inside the tunnel, a considerable amount of energy is being spent by the way of using ventilation and cooling systems to dissipate the heat. However, operational costs of the system increase quite considerably, especially as the mines get deeper. In this research, shotcrete is used both as a structural lining and as an effective thermal insulation to reduce the heat load on the ventilation and cooling system within such tunnels. The research was implemented in both the experimental and theoretical aspects.
  The experimental aspect, focused on the development of thermal insulation shotcrete. Expanded perlite aggregate (EPA) was firstly introduced into cast concrete mixtures by replacing the sands volumetrically in different ratios. The obtained samples were under the tests of mechanical properties including unconfined compressive strength (UCS) and splitting tensile strength (STS), etc. And thermal properties were derived by the transient plane source (TPS) technique. About 22% to 80% thermal conductivity losses of samples were noticed with the EPA additions, however still with certain strength. And then field shotcreting process was followed in the same mix design, it is found that the UCS and STS of most shotcrete samples were larger than that of cast samples, and the shotcreting process did not have obvious effects on the samples’ thermal properties with regard to cast samples.
  The theoretical aspect emphasised on the theoretical fundamental for thermal insulation on the surface of infinite rock mass. First, two-layered slab models were considered in both analytical and numerical means. Then, the cylindrical models that are more similar to tunnels for insulation were depicted further. Finally, a full three dimensional metal mine level was numerically simulated to evaluate the heat flow reductions in both full and partial insulation cases, on the basis of the thermal properties from the shotcrete. Results showed excellent heat load reductions in both full and partial insulations, with the developed shotcrete.

• Subjects / Keywords

  • Tunnels
  • Shotcrete
  • Thermal insulation

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R39K6S

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.