WATER JETS: CONCRETE YES, TUNNELING MAYBE.

High pressure jets are demolishing weak concrete faster and at lower cost. Will the payoff be as dramatic in tunneling and mining? In rock tunneling and mining, adoption of the concept lags here, but in Europe more than 60 water-jet equipped roadheader mining machines reportedly have been sold in the past three years. And last month the U. S. Department of Energy, Bureau of Mines and the Colorado Mining Association published a request for proposals for a joint industry-government effort to determine the advantages of water jets in conjunction with mechanical mining machines to mine oil shale. The goals are major improvements in rock-cutting productivity, energy efficiency and operating costs.