Evaluation and optimization of the integrity of HDD installed pipelines

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Horizontal Directional Drilling (HDD) is used to install pipelines and utilities beneath waterbodies, roads, and other surface obstacles where traditional open-cut construction is not feasible. The HDD process includes drilling a borehole along a pre-determined alignment, enlarging the borehole, and installing the pipeline by pulling it inside the borehole. The pipe being installed is subjected to a complex combination of stresses and strains that are not well understood. The stresses/strains that develop during installation have an impact on lifetime of the pipe operation. A more detailed investigation of the HDD installation requires evaluating axial and circumferential stresses, as well as the imposed strain on the pipe section as it is forced to conform to the borehole geometry. This research will include the analysis of stress/strain experienced by the pipe based on strain gauge measurements during actual HDD installations to evaluate the structural safety of pipelines.This research program will use a strain-measurement tool to record longitudinal and circumferential strains throughout the pipe installation under various conditions and different pipe sizes. This data will be analyzed to calculate axial, bending, hoop, thermal, and shear stress. These findings will be compared with theoretical calculations recommended by current industry standards. This analysis will provide a basis to investigate the application of more recent and advanced design codes for HDD installed pipelines, and identify any areas that may improve the current design guidelines. The stress/strain analysis will also include pipe lifting operations while the pipe section is being lifted and aligned with the borehole. A separate strain monitoring system will be conducted to measure the actual pipe strain where the pipe bends vertically, horizontally, and sometimes a combination of the two. Finite Element (FE) models will also be developed to be compared against the actual measurements. These models will be verified against field measurements, and the modeling input parameters will be calibrated. These calibrated parameters will be the basis for future models and designs.