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Corps of Engineers conducted a
<br /> test of pipeline responses to a
<br /> concentrated 10-ton blast (Ref. Sweet Dreams
<br /> 2). One end of a 6-in diameter,
<br /> • 220-ft long, pressurized pipeline
<br /> was located only 79 ft from .-,-,-_._k 7,r-�,• ,..,I. ,
<br /> -'
<br /> ground zero. Despite that the ' �../k. �, .
<br /> end being in the crater and ejecta ��':��;• '•,.r•.r._
<br /> zone and experiencing some per- 1r-;`
<br /> manent displacement, no visible
<br /> breaks occurred. Internal pres-
<br /> sure had dropped from 5(X) to -•
<br /> 400 psi, but no leaks could be ~
<br /> seen. Peak dynamic strains, all .-::-...e-; `'`
<br /> measured longitudinally, were '•` . -
<br /> •. \•
<br /> 1100-1400 pin/in and estimated • .,, '
<br /> total strains,including those from
<br /> ti
<br /> pressurization, would be about • •:ie, ,.,
<br /> 1550. The authors of the Corps' << ..);.t-.:-.;.;,...q.
<br /> report estimated yield stresses '°
<br /> and strains of 60,000 lb/in'and „.- '
<br /> 2,000 pin/in, respectively, and '" . g ``� y r`' i r
<br /> reported measured radial vibra• , - . ,
<br /> Lion of 168 in/s. •' •.•
<br /> The most extensive studies of
<br /> blasting and pipelines were con- \ •..
<br /> �- 911.0
<br /> ducted by the Southwest Research . .? .• -, ./"i:,-1:•.. '
<br /> Institute (SwRI) for the Pipeline '. ‘.• -
<br /> Research Committee(PRC)of the -.., :. 1
<br /> American Gas Association (Ref. �.•.'• -.4, • >• 1;•
<br /> 3-5). Their concerns were of ;t�.. ,,; ,).;,,. =<_'
<br /> both mining and close-in con- '.<: , rr;,•
<br /> •
<br /> struction blasting with small ,''i'`
<br /> charges. In their initial' studies, '�s��' �
<br /> they examined vibration propaga-
<br /> tion in soil and developed equa-
<br /> tions and nomography predicting After a long day,you've earned a good night's sleep. You'll sleep well knowing
<br /> stresses from pipeline characteris- that Nobel Insurance Company's claims management staff is ready to respond to
<br /> tics,distances and charge weights. emergencies day or night Call our Marketing Department today for information
<br /> These tests were done both at lab- about our liability insurance programs and the agent nearest you.
<br /> oratory scale and on two operat-
<br /> ing mainline systems of 24- and aip NOBEL INSURANCE COMPANY
<br /> 30-in diameter. Even though the (800) 766-6235
<br /> pipelines were full size, stand-off
<br /> distances and charge weights
<br /> were small, being 6-13 ft and
<br /> 5-15 lbs/delay for the 24-in pipelines. A follow-up study by hle the previous SwRI studies are
<br /> pipeline and 9-15 ft and 3-5 lbs SwRI for PRC examined blasting to full-scale mining blasts, they
<br /> for the 30-in. Such small distances in rock (Ref. 5). Again concern anticipate some comparisons in
<br /> were placing the pipelines close was for small charges, up to 20 the more comprehensive report
<br /> or possibly within the permanent lbs/delay. Measured strains were to follow.
<br /> or plastic ground strain zones. less than those from the previous- Dowding's text (Ref. 7)
<br /> The Enron Gas Pipeline Group ly found for the experiments in includes prediction equations for
<br /> developed a standard based on soil. Strains were very low pipeline stresses and strains
<br /> this SwRI research (Ref. n They except for a few measurements showing worst cases for low
<br /> applied the prediction egthttions made so close as to likely be in the propagation media. They address
<br /> with maximum dynamic stress cr1- inelastic deformation zone (as strains from bending and stretch-
<br /> teria of 1000 lb/in'for arc-welded close as 16 blast-hole diameters). ing and stresses based on ground
<br /> and 500 lb/in2 for acetylene-weld- Although the authors of this displacements.
<br /> cd or mechanically jointed report are unsure how compara- (continued on page 34)
<br />
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