Nonlinear Analysis of Interaction between Pipe and Borehole in Horizontal Directional Drilling Installations

摘要

The deformation of the borehole and the chocking (wedging) effect of surrounding soil on the pipe perimeter during the pull back phase may have a substantial effect on pulling force predictions for horizontal directional drilling (HDD) projects.However,this effect is not considered in existing methods for estimating the required pulling force.This paper provides a model representing the interaction between the pipe and soil,for which the soil is assumed to behave as a Winkler foundation.The stiffness matrix of a plane rigid-frame element considering such interaction was derived by variational calculus and the principle of minimum total potential energy.Moreover,a nonlinear analysis of the interaction model was conducted using the finite element method.The pipe displacement and chocking effect were investigated considering the pipe-soil interaction,and associated parametric studies were performed to determine the relative importance of the various factors.Pipe displacement is shown to increase with load and over-cut ratio,but to decrease with increasing oblateness of the borehole and modulus of foundation (subgrade) support.The chocking effect is shown to increase with load and oblateness,and decrease with increasing over-cut ratio and coefficient of degree of subgrade support.In addition,both the pipe displacement and chocking effect for an elliptical borehole are greater than for the circular borehole,under the same conditions.