EXPERIMENTS IN THERMAL SPALLATION OF VARIOUS ROCKS

The greatest limitation of the spallation process is its inability to spall (or to consistently spall) many rocks encountered in petroleum d rilling and mining operations. The New Mexico institute of Mining and Technology has conducted a series of experiments to investigate the po ssibility of expanding the use of the spallation process to the penetr ation of rocks generally considered not to be spallable. The methods u sed during this work were I) spalling at temperatures below that produ ced by the stoichiometric burning of fuel oil and air, and 2) spalling by alternately hearing and quenching the rock surfaces. No success wa s experienced in spalling at the lower temperatures but initial rests showed the alternate heating and chilling system to be successful part icularly in penetrating travertine limestone. However, continued testi ng indicated that, unless the rocks are extremely uniform in compositi on, spalling will result in highly irregular holes or holes that canno t be directionally controlled.