Rockdumping may be necessary for pipeline UHB mitigation, crossings for separation, protection and stability. It is imperative that the structural reliability analysis for UHB is assessed with all aspects and factors taken into account to predict accurately the amount of rock and download required to ensure the integrity of pipelines. For UHB mitigation design, there are a number of analytical models available for download calculations to determine rockdump schedule.
This paper examines and highlights some fundamental issues and pitfalls for rockberm design with respect to UHB download assessment. The lateral breakout has been previously addressed by some engineers and researchers. The potential risk for pipe to breakout from the rockberm is studied herein focusing on the vertical direction due to upheaval load.
Based on the theoretical analysis and numerical FEA modelling, it is demonstrated that the common practice for rockbern design is not consistent resulting in unconservative rockdumping for UHB stability. Further design optimization can be compromised by lack of understanding of the failure mechanisms. Uplift resistance for stratified and layered soil types applicable for rock enhancement is also discussed and formulated. The design principle and rationale for selecting an appropriate rockberm profile and its sizing is proposed. Its effect on the UHB is illustrated by a detailed theoretical analysis and a series of numerical simulations with respect to pipeline dimensions.