Evaluation of close-in blasting effects on welded steel pipelines

Occasionally, it is necessary to perform blasting close to buried, welded steel pipelines to excavate foundations or roadway cuts, conduct mining operations, or to construct an adjacent pipeline trench. The primary hazards associated with blasting near pipelines include permanent rock mass displacement owing to delayed gas pressures and ground strains from wave propagation (compressive, shear and surface waves). Current pipeline standards do not address these limitations for blasting in proximity to buried pipelines. Existing methodology is often applied quite conservatively in the form of permissible ground particle velocity thereby limiting ground strain, which leads to increased costs for the party conducting the blasting and/or the pipeline owner who must provide pipeline protection. This paper presents methodology and guidelines for the evaluation and protection of buried pipelines subjected to the effects of blasting. The examples given in the paper represent a departure from the normal practice of specifying blasting restrictions on buried pipelines, because they are based on higher peak particle velocity limits than suggested by other researchers and currently adopted by a number of pipeline companies. General recommendations are provided for evaluating the strains induced into buried pipelines and avoiding the effects of mass movement of rock due to delayed gas pressure. The general goal for this paper is to produce methodology and guidelines that are equally applicable and realistic for both the pipeline owner and the party conducting the blasting; however, they should not be considered to be recommendations for any specific future project.