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Compared to previous studies, strains were relatively low for given particle velocities. Tlie large blasts involved in this study produced high • particle velocities at relatively large distance. Hence, the pipelines experienced Nigh vibration amplitudes at distances beyond the inelastic zone. In addition, charges are in blastlioles, being vertical columns which are long compared to the closest blast to pipeline separations. 8y contrast, the previous studies involved close-in "point" sources. Interesting is the apparent limiting effect of pipeline responses. Circumferential strains, in particular, do not continue to increase in proportion to increasing surface particle velocity. This could be from lack of total coupling with the ground. Another possibility is that the spatially extended charge with its relatively long detonation time impacts the pipeline less than a point source type blast. Tl~e hypothesis requires further analysis. Stresses Stresses were calculated for each blast using maximum circumferential and longitudinal strains (table 4). As with previous SwAI studies by Esparza, these were assumed to be principle plane strains, and represent a type of worst case (as in pseudo vector sum compared to true vector sum). Esparza's values of Young's modulus (29.5 x 106) and Poisson's Ratio (0.3) were used (Ref. 5). Stress values calculated from these tests are based on pseudo sums of longitudinal and circumferential. An initial examination of time- . correlated strain components found that peaks did not occur at the same tune. Phase is also important in calculating the stresses corresponding to given strain states. If the two component are opposite (one tensile and one comprehensive at any instant), the calculated stresses are actually less than would correspond to either uniaxial strain. Circumferential or hoop stresses from internal pressurization can•be easily calculated from the thin-walled cylinder equation; Stress (lb/inz) = PD/2t where P is pressure, lb/inz; D is inside diameter and t is wall thickness, both in inches. Table 5 lists pipeline specifications and hoop stresses produced by internal pressurization. As the table shows, the pressurization= induced circumferential or hoop stresses are close to 72 pct of yield strengths (and would be exact if D was set to outside diameter). The PVC is also an exception for reasons unknown to the authors. Also in table 5 are both stresses and strains equivalent to 18 pct of yield strength. This 18 pct level is used by some transmission companies as an informal guideline for transient environmental effects such as traffic over a pipeline beneath a highway. The minimum biaxial strain values in table 5 (last column) were calculated from the stress-strain equation in table 4 based on the worst-case assumption that the two strain components peak at the same time and are the same peak amplitude. They are minimums in that they are tl~e lowest (most restrictive) values that correspond to the 18 pct of SP1YS stress. 134