Abstract
Overloaded blastholes and insufficient stemming are major factors in flyrock accidents at surface metal and nonmetal mines. Accurate measurement of blasthole depth, stemming height, and water depth would reduce the overload and the probability of blowout, flyrock, excessive ground vibration, and airblast. Problems result because current measuring systems are inaccurate and often difficult to use. A literature survey determined measurement techniques and blasting parameters prior to 1970. Similar data were gathered for current practices in 11 iron mines, 30 copper mines, and 92 quarries. Most operations used a cloth tape to measure borehole depth and stemming height; approximately 10 of the operations had dry blastholes. Candidate measuring techniques with best potential for improvement over the present weighted tape method are disposable tapes or string chains, automated readout tapes, modified sludge level indicators, and acoustic reasonance methods.
