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<br /> <br />Settlement <br />A small amount of settlement was <br />conducted to show dimensional changes. <br />all 5 pipelines settled by amounts of 0 <br />survey on September ]4 (40 days) found <br />ft (.34-.49cm). Strains from the small <br />very small. <br />found by laser transit surveys <br />Between 14ay 1 and AuyusL 5 (90 days}, <br />.O]] to .025 ft (.34-.76cm). Another <br />additional settlement of 0.011 to .016 <br />amount of differential settlement are <br />ANALYSIS <br />The last mining cycle brought the production blasting within 48 ft of <br />the closest pipeline (blast 29). ilrer-e was little backbreak and no apparent <br />permanent ground displacement at this minimum distance of 44 trole diameters. <br />Vibration levels were 25 in/s for llris blast on the ground surface and 9.2 to <br />10.8 on the trio instrumented pipelines with no loss of pipe integrity <br />(pressure drops). Figures 6 through ]0 show measured strains, are composites <br />of two types of blasts, different aziinutiral directions and 5 pipelines of two <br />different materials. It is not sur•prisiny tlral considerable scatter exists in <br />the summary figures, although a pipe-by-pipe analysis is better, Tfris will be <br />shown in the follow-up comprehensive report. Also in common with other <br />studies, there were problems with use of strain gages and electronics in an <br />unfriendly environment and for an extended period. Generally, circumferential <br />strains were hiylrer than lonyitudirral by a r-ouylr factor of two and PVC strains <br />Iriyher than steel again by about the same factor. Further analysis is <br />anticipated. <br />Blasting Criteria for Steel Pipelines <br />Criteria are needed for blasting near pipelines that will insure that <br />damage will not occur and yet be reasonable whir regards to resource recovery <br />and other requirements for blasting. Ttre exact definition of "damage: is yet <br />to be established but certainly includes any failures leading to pressure or <br />product less and any plastic deformation. lire Enron Standard (ref. 6) <br />specifies allowable stresses of 1,000 lb/inZ for electrically-welded pipelines <br />and 500 lb/inZ for gas-welded or mechanically joined steel pines. As table 4 <br />shows, these stresses have already been yr•eatly exceeded. Mentioned <br />previously, was one guideline which allows 18 pct of yield strength for <br />transient environ-mental excitation caused by highway traffic. if this 18 pct <br />guide were adopted for blasting, then stresses and strains listed in table 5 <br />would apply. It is not unreasonable to allow such a criterion for blasting as <br />it is unlikely that a pipeline would simultaneously be subjected to trafFic <br />stress and high-level blast vibration. For• analysis of dynamic stresses being <br />added to static (from pressurization), only circumferential are probably the <br />most critical because of longitudinal constraint. Not only are blast-produced <br />circumferential strains larger, but they must be added to those resulting front <br />pressurization. Longitudinal strains are from lire transient sources alone <br />plus a relatively small component composed of Poisson's factor and some <br />possible static bearding. <br /> <br />• <br />135 <br />