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SOBIE AND ASSOCIATES, INC. PAGE 2 Paulson And Sons Inc . January 26 , 1993 Attention: Mr . Bill Paulson Re : Bill Paulson Quarry Blasting The above information provided by Mr. Scott Mentink, KPI in telephone conversation. In order to assist in the understanding of blasting operation ground transmitted vibration affects and their damage potential , the following discussion is provided. We apologize for this effort if the reader' s under- standing and knowledge , at this time , is such as to find the following information needlessly superfluous . BLAST VIBRATION CONSIDERATIONS The detonation of confined explosives in the earth result in earth fracture and movement of material which confine the blast . Nearly all of the blast energy is utilized in producing fractures and in moving the material in the immediate area of the blast . A remaining portion of the energy produced by a blast is released into the earth and partially into the atmosphere . The energy released into the earth is propogated through earth materials as elastic waves , while the portion which escapes into the atmosphere is productive of air concussion. The earthborn surface waves (elastic waves ) are similar to the waves produced on a smooth surface of water when a stone is thrown into the water. There are two important differences between the ( illustrative ) water waves and the earth -wave s . - First , the height of the earth wave is generally but a few thousandths of an inch . Second, the earth wave length ( that is the distance from the crest of one wave to the crest of another wave ) is approximately 300 feet. Structures supported on, or within a few feet of, the earth surface ride the surface waves in a manner similar to a .cor.k floating on water. The height of the surface wave , (displacment) at any point depends on the amount of energy detonated, which is designated as the maximum explosive weight detonated within the blast at one instant of time , and the distance the wave has traveled from the blast . The frequency of ground motion ( the rate at which the displacement repeats itself) depends upon geologic conditions . The value of "peak ground particle velocity of ground motion" (PPV) is generally described as the vibration characteristic which can be used to best define the probability of blast vibration damage . The determination of PPV is dependent upon both the Displacement and the Frequency of ground motion, when used as a measure of damage potential to structures . As regards ground transmitted vibration , the two factors which most influ- ence the vibration intensity at a structure are : 1 . The maximum amount of explosive detonated per delay interval within the blast . 2 . The distance between the blast and the structure under consideration.