Strain monitoring and analysis of a steel pipe during horizontal directional crossing

Horizontal directional drilling (HDD) plays an increasingly important role in municipal pipeline construction in congested urban areas. Knowledge of the mechanical behaviors of a pipeline during HDD installation is significant for the design of an optimal construction scheme and the strategy making of life-cycle maintenance after installation. In combination with a practical project, the in-situ monitoring of a gas pipeline during HDD construction was conducted. Based on gyroscope position-detection system and fiber optic sensing technique, the three dimensional (3-D) spatial coordinates of the pipe position and the strain responses of the tested pipe segment traveling through the whole drilling track were measured. A theoretical model is presented to simulate the pipe pullback process and calculate the strain in the pipe during installation. The actual mechanical behavior of the pipe subjected to large bending deformation is particularly concerned. The case of the monitored HDD construction is examined to demonstrate the application of the model by comparing with the measurements.