( 1 JULY-30 SEPTEMBER 1971 ) USE OF ELECTRON BEAM GUN FOR HARD ROCK EXCAVATION

Abstract : An electron beam gun (EBG), which is not funded by the contract, is operational at low power and will be shipped to the field site in 4 to 6 weeks. Design and manufacturing effort on the EBG carriage was completed in June, and the carriage is undergoing preliminary operational and calibration tests. The Raymond Granite Company's quarry, located near Yosemite National Park, has been selected as the test site, because it has extensive sources of unfractured rock. A mathematical model has been developed that can describe the piercing of the rock by the electron beam and the thermal stresses subsequently produced. Trends in the time development of the calculated stress fields confirm laboratory observations for at least one geometry.