Strengthening Rock by Injection of Chemical Grout

Chemical grout was injected into locally unstable areas in fractured granite in the North American Air Defense Underground Combat Operations Center (NORAD) near Colorado Springs, Colorado, and the results were considered successful because measurements indicated that rock movement stopped. The chemical grout used was a specially formulated epoxy resin which was selected after laboratory tests and a test injection at the location where it was to be used. A polyester resin grout was also tested and both grouts are described. Items which should be considered when planning a chemical grouting operation, including the chemical grouts, equipment, and procedures are discussed. The results of laboratory tests are analyzed and recommendations for investigations which would improve the results of chemical grouting are presented.