Study On Deformation Characteristics Of Buried Pipeline Crossing Loess Embankment Area

In the process of urbanization of loess plateau in China,loess filling is a kind of typical and common engineering measure.The uneven settlement of the filling soil will inevitably lead to deformation or even damage through the filling area.It is necessary to study the deformation characteristics of the buried pipeline through the loess filling area.Taking the buried pipeline in Yan'an New District as the object of study,through the data collection and field investigation,the regional settlement characteristics of the filling area are summarized,the deformation model of the pipeline is summed up,the mechanical model is established and the mechanism of pipeline deformation is obtained.The indoor model test was carried out on the piping through different forms of filling,and the variation of pipeline displacement,strain and lower earth pressure under different inhomogeneous settlement were obtained.Finally,numerical simulation of MIDAS software is carried out to further study the deformation characteristics of buried pipeline through loess filling area.The study has achieved the following results:(1)Through the field investigation,the paper summarizes the settlement form of the fill side,the form of the "oblique line",the "convex" settlement form,the "concave" settlement form and the three combinations.(2)The deformation modes of the buried pipeline through the fill area are as follows:shear deformation mode,buckling deformation mode,beam compression deformation mode,torsional deformation mode and compression deformation mode.(3)It is concluded that the maximum displacement of the pipeline occurs at the most distant distance from the uneven settlement surface in the fill area of the filling area,and the variation of the pipeline displacement at the uneven settlement surface is obtained.The displacement curve of the pipeline is "S".The upper surface of the pipeline is affected by the tensile stress during the whole test,the tensile stress is the largest at the uneven settlement surface,and the tensile stress is the smallest.The lower earth pressure at the lower part of the pipeline is the largest decrease in the uneven settlement surface,and the pipeline in the fillingsubsidence zone is in the floating state.In this mode,the deformation of the pipeline is mainly prying deformation mode.(4)The maximum displacement of the pipeline occurred at the end of the pipeline in the settlement area of the two sides.The displacement of the pipeline at the uneven settlement surface was larger than that of the pipeline The sedimentation curve is parabolic in the middle of the relative stability zone.The strain value of the upper surface of the pipeline is negative at both sides,and the relative stability of the middle filling is positive.The maximum value of the pipeline strain occurs at the midpoint of the middle filling area and is symmetrical.The lower earth pressure at the lower part of the pipeline is the largest decrease in the uneven settlement surface.During the settlement process,the pipeline is in the floating state on both sides of the filling area.(5)The maximum displacement of the pipeline occurred at the midpoint of the middle fill sedimentation area through the settlement of the "concave" sedimentation zone pipeline model.With the increase of the displacement of the pipeline at the uneven settlement,the sedimentation curve The middle of the settlement is located in the middle of the parabolic shape.The strain value of the upper surface of the pipeline is negative at the filling area,and the relative stability of the two sides is positive.The maximum strain of the pipeline occurs at the midpoint of the settlement area and is symmetrical.The lower earth pressure at the lower part of the pipeline is the largest decrease in the uneven settlement surface.During the settlement process,the pipeline is in the floating state in the filling area.