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hhite Engineering Associates, Inc. <br />Report No. 79219-D June 18, 1979 <br />Utah International, Inc. Page 5 <br />The overall level of ground vibration, as illustrated by these <br />• measurements, is still far below the generally recognized criteria for <br />structural safety, and the airblast was inconsequential at stations where <br />measurements were obtained: Both blasts were well within the design <br />criteria established by OS?i. <br />Some mention was made during m}• visit to the mine of the possibility <br />that~a higher water table in the E Pit area might be the cause of the seemingly <br />higher levels of vibration. Ithile this could certainly be a minor contributing <br />effect, I am of the opinion that the short time duration of these large blasts <br />is the principal cause of the increase in observable vibration levels at the <br />power house and in the mine office. <br />The seismograms from Stations 1, 3 and 9, all at close range, show <br />the pulse form to be one large single pulse very similar to tie type produced <br />by a large undelayed blast. An extended duration will allow more time for the <br />seismic effects of individual delay elements to dissipate before being affected <br />by subsequent delay periods. <br />The principal cause of blasting vibration problems has always been, <br />and will continue to be, a matter of hu~;~an perception. Observers within a <br />structure Lhat is responding in phase to ground vibration, which causes <br />amplification within the structure, tend to become more alarmed than observers <br />of the same blast who are outside the structure. <br />Because of the nature of this area, and the need to utilize large <br />blasts for purpose of economy, it will be extremely difficult to design. <br />blasts that are not observable by some people at great distances. <br />Since the results of these tests conform very closely to previous <br />tests, the only recommendation we will offer for further reduction of peak <br />amplitude is to extend the time duration for total detonation. <br />The following illustrations are attached and complete this report: <br />Sketch D1ap <br />- Tables I, II and IIT ~'_ <br />Graphs I, IA, II, IlA and III~r ~:.~ <br />14 Scismogi'ains <br />Copy of Bar Graph Charts <br />Instrument Specifications <br /> <br />DSB/al <br />Copy: hfr. R. C. Dic~lcrich <br />Utah International, Inc. <br />R'HI EN GF I^' S. CIATE iNC. <br />r <br />`G - / .iC <br />David S. bowling <br />Consulting Gcophysicis~ <br />L-5 <br />