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PIPELINES The sources for the following comments are in-house reports and "Relationships Between Pipe Stress, Ground Particle Velocity and Scale Factors in Blasting Dolomite" by Dennis Allen Clark, Regional Manager, VME-Nitro Consult, Inc.. In the early 1960's work was undertaken by the American Gas Association Pipeline Research Committee to establish limits for charge size (pounds per delay) and distance from a blast to high- pressure gas transmission lines. The primary research found that there had been no reported case of pipeline failure due to normal blasting activities. Only when explosives were detonated directly adjacent to a pipeline were failures recorded. To be able to predict if the stress produced in a pipeline by nearby blasting activities is enough to cause failure one must assume: 1. Soil displacements can be adequately predicated by scale distance formulas. The pipeline movements are equal to those of the surrounding soil. These assumptions result in a very conservative predicted free field soil stress. Two types of pipe stress are considered: axial stress, and circumferential stress. The allowable pipe stress is determined by American Petroleum Institute guidelines. Pipe diameter, pipe wall thickness, specified minimum yield strength, maximum operating pressure, pipe modulus, and the design factor must be known to calculate this. Other factors that should be considered include: thrust blocks, thermal movements, residual stresses, overburden thickness, and pipeline condition. Unfortunately, it is hard to obtain this information for most older pipelines and many new pipelines. In one example, a pipeline company requested that the maximum allowable pipe stress be held to 2,500 PSI. The pipeline was measured with strain gauges and seismic particle velocity recorders. The 2,500 PSI allowable pipe stress was never reached but the closest blast was five feet away from the 22" diameter pipe and did have a measured particle velocity of 9.85 inches per second. For the best protection, pipe condition, pipe attributes and design factor should be known, and both strain gauge and particle velocity measurements should be taken.