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Citizen Intere~ <br />Q <br />Ground motion, or ground vibration, can be experienced in <br />different ways. Avery low frequency vibration, such as might be <br />experienced from a large blast on a mine along way off, might not <br />be recognized as a vibration, only as sense of unease, or even a <br />passing feeling of slight giddiness. Higher frequency and higher <br />intensity motion is much more obvious .and recognizable, <br />particularly if the structure responds. Humans are frequently <br />disturbed by vibration levels chat are perfectly permissible under <br />the OSMRE regulations. This is discussed in the manual under the <br />heading of "H(IMAN St,BJECTIVE TOLERANCE" in Chapter S, pages 35, 3b <br />and 37. <br />Sdhen vibration levels occur which approach or exceed the <br />regulation limitations, there is no doubt at all that most people <br />find this unpleasant, and their cause for alarm is normally quite <br />justified. It is the reason why most consultants advise their <br />clients to try to keep well below the regulatory levels, and only <br />plan to risk approaching them when blasting in those locations must <br />be carried out. <br />A cormon complaint involves t <br />person is at rest in his home, and t <br />blast causes the crockery to rattle, <br />and frequently worries about whether <br />caused any damage to his home. In <br />however, it is sometimes noticeabl <br />simply when a person walks across the <br />out, it may be that that person, in <br />that this was happening. Sometimes, <br />knowing that the rattling is due to <br />rot worrying, but when it happens due <br />~aho knows what that might have done! <br />he rattling of crockery. 4hien a <br />he vibration from a nearby mine <br />then he is disturbed by this, <br />such a vibration could have <br />investigating such complaints, <br />e that the crockery rattles <br />floor. When this is pointed <br />motion, just did not realize <br />though, the parson admits that <br />a normal household activity is <br />to action of explosives, then <br />Apart from the normal activity of the occupants, a structure is <br />subjected to daily, seasonal and incidental outside causes of <br />notion. Some are very slight, and unnoticeable to the casual <br />observer, such as daily and seasonal temperature changes. The <br />structure, however, is nevertheless affected by such temperature, <br />and therefore dimensional, changes. Seasonal moisture differences <br />can cause the ground the house is built on to expand and contract. <br />More obvious causes of structural movement are high winds, <br />chunderstoms, and eazthquakes. Neazby highways or railroads, and <br />of course aizports, can all cause vibrations. <br />Even unoccupied dwellings, if left undisturbed, will eventually <br />deteriorate to the point of collapse. <br />ACTUAL BLAST VIBRATI011 EFFECTS <br />One very important consideration concerns the re of a <br />structure to a blast vibration. This has already been referred to <br />116 <br />U <br />~~ <br />L,! <br />~` i <br />{~ <br />