Application of Refraction Tomography to Map the Extent of Blast- induced Fracturing.
Cumerlato-CL; Stachura-VJ; Tweeton-DR
Paper in Key Quest in Rock Mech : Proc of the 29th Us Symp Minneapolis, Minnesota,6/13-15/88 PP 691-698 :691-698
The U.S. Bureau of Mines has conducted high-resolution refraction surveys at a limestone quarry both before and after standard production blasts where variations in the blast design were made. The data collected were processed using a tompgraphic inversion algorithm to produce maps (tomograms) of the seismic velocity field of a shallow refracting layer in the rock left standing. Overlapping of surveys, velocity measurements from shotholes (preblast), and measurements of predominant joint sets were used to verify results. Resulting tomograms show sublinear low-velocity zones whose orientations correspond to those of measured joint sets. Low-velocity zones near pitwalls are interpreted as the extent of intense fracturing caused by blasting. These results demonstrate that refraction tomography can be a powerful and economical tool for locating predominant jointing and areas of preexisting or blast- induced fracturing--an important aid to operators during premine planning and blast designing.
Paper in Key Quest. in Rock Mech.: Proc of the 29th Us Symp, Minn. Minnesota, 6/13-15/88, PP. 691-698