Numerical Simulation Study Of Horizontal Directional Drilling Pipeline Backhaul Process

With the rapid economic development and people's increasing awareness of environmental protection,the traditional pipe laying excavation technology has long been unable to meet people's needs.Horizontal directional drilling technology has developed rapidly with advantages of environmental protection,small disturbance,and high efficiency,but its theoretical level.It is far from being able to meet actual engineering needs.In many cases,it needs to be determined based on experience.Subjective factors have a greater impact,so it is necessary to study the process of dragging horizontal underground drilling pipelines.In this paper,first of all,the force analysis of the dragging process of the pipeline is carried out,and the formulas and principles of the commonly used drag force are studied in detail.The advantages and disadvantages of different formulae and their applicable scopes are obtained.Then,starting from the local,the pipeline mechanics The performance is studied as the entry point.According to the theoretical analysis and simulation analysis of the local pipeline when the actual engineering pipeline is being pulled back through the reaming step and the curved section,the variation law and relevant conclusions of the local stress and strain of the pipeline are obtained.It has important reference value for practical engineering.The main research work is as follows:(1)Analyze the characteristics of the typical complex strata and its difficulties in crossing,and study the factors that affect the back drag of the pipeline and the drag reduction measures in the pipeline back drag.(2)Method for calculating the back drag force of commonly used pipelines: GB50423 standard stipulates rig back drag formula calculation method,unloading arch earth pressure calculation method,net buoyancy calculation method,winch calculation method and its basic ideas for comparative analysis,and through engineering examples The calculations and comparative analysis of the calculation results show that the advantages and disadvantages of each calculation method and the scope of application,and the unloading arch pressure calculation method and winch calculation method to improve,draw a better back towing force calculation formula;(3)theoretical analysis and related numerical calculations of the hole expansion step,and use ABAQUS finite element simulation software to establish the pipe soil finite element model,and analyze and verify the force state and pull back force change trend in the process of pipe crossing the step.The effect of the reaming step on the drag-back force of the pipeline under different parameters such as the height of the step and the change of the radius of curvature of the step;(4)Through the simulation study on the back drag process of the pipeline after passing throughthe bent section of the in-situ soil and the curved section of the excavated soil,the influence of the bending curvature of the pipeline and the hole/pipe ratio on the increment of the pipeline stress and back dragging force is obtained.