Mechanics Analysis Of Pipeline In Back-dragging Process Of Horizontal Directional Drilling

In recent years,Horizontal Directional Drilling(HDD)has drawn more and more attention in non-excavation pipelining project because of its advantages as great environmental adaptability,construction safety and fast.On account of the final and most important step of HDD,only a completed pipeline pullback engineering task can ensure that the whole project investment in the prophase work of human and material resources were not in vain.As a result of the limitation of working conditions,the pipeline pullback project must be done continuously after the start of the construction,and it can't be stopped in the middle.Hence,it's very important to optimize the related parameters by using mechanical analysis method before the pullback project.Above all,this article has carried on the research work as follows:Base on the technology of HDD as well as the pipeline pullback process,it has been found that there exist three locations called pipeline bent position,pipeline pullback unearthed position and the segment of interim tangential path,and respectively analyzed and summarized the larger influence parameters of the three.In the process of pipeline lift,through the method of finite element calculation and the validation experiments,it rules out that there would be no real components participated the interaction,and by building the new finite element calculation of the lifting process and compared with the experiments,it is found that the new model is with high accuracy,and it can replace the original model for the simulation analysis.By analyzing the results of finite element model and the model adopted in the experiment,the theoretical model of the simple-supported beam beam is deduced on the basis of original model,through the boundary conditions it has been completed to the solution of the model.Finally,the best pullback height is found by the engineering calculation.Compared with the results of finite element analysis,this model has high accuracy,and can be used as the analysis of pipeline lift.The stress of the pipeline in bending section is more complex,and this paper analyzed this by comparing with the existing models and found that they do not consider the effects of stiffness,and it doesn't accord the development trend of the pipeline crossing,so the new calculating formula was established by mechanic's analysis.Combined with the new model of the incremental computation of the derivation of bending section,it analyzed the whole calculation progress.This model can calculate the drag force at any time of the drag process.Finally,through the calculation of the three instances,it's found that the new calculation model conforms to the drag force better than any other models.In the end,by using the establishment of theoretical model in the process of the pipeline crossing artificial control to analyze the important construction parameters,it obtains that the best parameters can be chosen of the engineering practice.