Experimental Response of Steel Pipelines to Close Trench Blasting

ABSTRACT:

When protecting pipelines from third party activities, it is beneficial for operators to apply very conservative criteria for safe blasting. Recently, however, demands for increased capacity have required adding pipelines to existing rights-of-way, often close to or between existing pipelines. In these cases, overly-conservative blasting criteria can result in significant expenses and delays. The reported tests supply blasting stress data on full-scale pipes configured to simulate trenching in close proximity and parallel to an existing pipeline. Two sets of tests have been performed at a location with rock anticipated to be similar to that known to exist along a planned pipeline route. The pipes were instrumented at a number of locations prior to burial. Ground vibrations were recorded using seismographs during each shot. A variety of test blasts were performed, including advancing staggered line shots with delays, grids of charges set off simultaneously to simulate sympathetic detonations , and grids of decked charges. Charge weight ranged from 7.4 to 17.2 lbs/hole at distances from 15 to 25 feet from the pipes. Measured blasting stresses are compared with predicted values. Data from classic SwRI tests is included for comparison. Appropriate safety factors for close trench blasting based on the test data are considered. Measured stress values from simultaneously detonated lines of charges are compared to predicted values, which are typically of concern when the potential for sympathetic detonation is considered. Neglecting the potential for simultaneous detonations may result in significant error. Also, the measured PPV as a function of the scaled distance and a correlation of the blasting stresses with the measured PPVs are provided.

Matta, L., “Experimental Response of Steel Pipelines to Close Trench Blasting,” Paper No. IPC2016-64226, Proceedings of the 11th International Pipeline Conference, September 26-30, 2016, Calgary, Alberta, Canada.