Search

The displacement of pipe-soil contact points in the radial direction and the wedging effect of surrounding soil on the pipe perimeter during pipe pulling-back may have a substantial effect on predicting pulling forces for horizontal directional drilling installations. However, the influence of pipe-soil interaction on pulling force predictions is not considered in existing methods to predict the required pulling force. This paper provides a model representing the interaction between pipe and borehole. The mechanical characteristics of the pipe-soil interaction were numerically investigated with program ANSYS. Two parameters, the wedging coefficient and pipe displacement, were defined and associated parametric studies were performed to analyze the influences of relative factors based on a Yangtze River crossing project. The wedging coefficient is shown to increase with external load and ovality of the borehole, and decrease with increasing over-cut ratio, Poisson’s ratio and elastic modulus of soil. It can improve the prediction accuracy to consider the wedging effect since the difference among predicted results caused by wedging effect can differ up to 7.7% in example analysis. [ABSTRACT FROM AUTHOR]

This work is motivated by the need for prediction of pulling forces during pulling back phase in the horizontal directional drilling (HDD) installations for steel or polyethylene pipe. Six current prediction models are reviewed and components of pulling force resistance used in calculations are discussed. Two HDD installations are used to evaluate the accuracies of six models, including a 1816.2 m steel pipe crossing of the Yangtze River, Nanjing, China, and a 200 m polyethylene pipe installation at the University of Waterloo, Waterloo, Canada. Comparison of the results show that Driscopipe method and Drillpath method underestimate the maximum pulling forces in both steel pipe and polyethylene pipe cases, ASTM F 1962 method underestimates the maximum pulling force in steel pipe case while PRCI method and NEN 3650 method overestimate the maximum pulling force in polyethylene case, PRCI method, NEN 3650 method and developed PipeForce method are suitable for steel pipe case, ASTM F 1962 method and the PipeForce method are acceptable for polyethylene pipe case. [ABSTRACT FROM AUTHOR]