Theoretical Model to Predict Pulling Forces for Horizontal Directional Drilling Installations

摘要

The paper presents a model for predicting pulling force during pulling back phase in horizontal directional drilling.The analytical method develops the method given by Polak et al.in three aspects: (1) the soil is described by Winkler model and it constitutes an elastic support for pipe during pulling back phase,(2) considering the nonlinear rheological properties of slurry,power law model is used in calculation of fluidic drag friction,and (3) the resistance exerted on drill string is considered and pulling force at carriage is calculated.Except for the weight and weight friction of pipe outside pilotbore and fluidic drag friction,components of pulling force are calculated considering the effect of pipe-soil interaction by two parameters,namely pipe displacement and coefficient of chock effect which represent the displacement of pipe-soil contacting point and the clamping effect of soil on pipe in cross section during pulling back phase,respectively.A numerical program is compiled according to the given method.Comparison of HDD field data and predictions of pulling force indicates that the proposed method is rational.