Evaluating the Penetration Depth of Rock Falls on Buried Pipelines

Abstract Buried pipelines are usually less susceptible to rock falls compared to exposed utilities because soil cover protects them from direct rock fall impacts. However, in instances where pipelines are situated in mountainous terrains, the risk of rock falls penetrating through the protective cover becomes a concern. In these circumstances, the risk of rock fall to the pipeline should be assessed and managed. This paper, first, outlines a framework for assessing the rock fall risks to buried pipelines based on a general risk matrix. One of the key parameters in the matrix is the likelihood of rock fall penetration depth. To estimate this parameter, the penetration depth of the rock falls should be estimated and compared with the actual pipeline depth of cover. The existing theoretical relations commonly used to estimate rock fall penetration depth are then presented and critically reviewed in the paper. Finally, the penetration depths resulting from two actual rock fall incidents in the buried pipelines are back-calculated using theoretical relations and compared with the real measured penetration depths. The case histories occurred in a pipeline in 2006 and 2023. The comparison between theoretical estimations and the real measurements demonstrate that the existing theoretical relations generally underestimate the rock fall penetration depth. Therefore, relying only on the existing theoretical relations could lead to an underestimation of the rock fall risk. As a result of our study, we propose several recommendations to enhance the accuracy of estimating rock fall penetration depth and its associated likelihood in the risk calculations.