An Investigation of Thermal-Mechanical Fragmentation of Hard Rock
Abstract
Based upon research using heat applied to the surface of rock and at the base of slots cut in the rock, it was determined that heat applied internally is markedly more effective in fracturing hard rock. Coiled wire resistance heaters proved effective in fracturing 30 in. cubes of rock in the laboratory. They also were employed to fracture granite in place, but burned out in a short time in bore holes. Carbon arcs were found to be economical and effective heat sources. These were employed in three and four hole geometries to fracture rock with three faces, and a plane of fracture parallel to the working face was consistently formed. Fracture is augmented with rock splitters which also remove blocks from the working face. Finite element studies have been made of temperature and thermal stress distribution in support of field research. The concept is being developed to drill a tunnel round with pneumatic drills, with heat to fracture the rock in a manner analogous to an explosive round. Slot, V, and pyramid cuts are being tested. Projected rates of advance and costs per foot are favorable.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1973
- Accession Number
- AD0772987
Entities
People
- George B. Clark
- Mahen Patel
- Terry F. Lehnhoff
- Vernon Allen