Mechanical Characteristics Analysis Of Crossing Soil Landslide Steel Pipeline And Anti-slide Pile Reinforcement

The geological conditions in our country are complex and diverse,and there are many mountainous areas and plateaus,so the landslide hazards are very common.Where the site conditions are limited under special circumstances,the long distance oil or gas transportation pipeline would cross the landslide region inevitably.The pipeline failure would happen range from deformation to fracture,fire or explosion under the effect of a landslide.Therefore,it is particularly necessary to analyze the stress characteristics of the oil or gas pipeline crossing the landslide.In order to further protect the oil or gas pipeline,anti-slide piles should be set to reinforce the landslide body and reduce the pushing force to pipeline due to the displacement load of landslide.Due to the complexity of using finite element to simulate the integrated process,including the pipeline stress analysis and landslide reinforcement using anti-sliding piles,the process can be divided into there steps.Firstly,the landslide stability and the discrete displacements along the pipeline can be calculated.Secondly,the calculated discrete displacements can be used as loads applied on the pipeline to analyse its stress characteristic.The two models including pipeline crossing landslide in latitude direction and in longitudinal direction can be studied respectively.Meanwhile,the influence of pipeline internal pressure and temperature difference on the two models mentioned above can also be analysed.Finally,anti-slide piles can be used to reinforce the landslide body,and the factors such as pile depth,pile length,horizontal layout and longitudinal layout on slope surface are optimized in order to protect oil and gas pipeline crossing the landslide in operation stage.In order to calculate landslide stability and the sliding displacement using finite element method,the share-strength reduction method can be adopted.In the simulation process,the Mohr-Coulomb model is used to simulate soil property,and the strength of slope can be reduced by adjusting the soil property in order to realize land sliding process.The calculation results include the share-strength reduction factor of the slope,and the discrete displacements value and directions along the slope with buried pipeline.In order to analyse the pipeline stress characteristics,the soil can be simulated by spring element,and the pipeline can be simulated by pipe element,whose property can be calculated by Ramberg-Osgood model,in numerical analysis software.For the numerical simulation analysis of landslide reinforcement using anti-pile,the share-strength method and contact model can be built.Based on the model,the stress characteristics of the anti-slide pile can be analysed varying with pile length,pile diameter,and the conclusions can be used as reference for anti-slide pile design.The layout of the anti-piles in longitudinal and latitudinal direction can be optimized after analysing the strength of the slope reinforced by anti-slide piles.Meanwhile,the various methods used for calculating the slope stability are also summarized.After studying the conclusion can be found as below.Under the condition of pipeline crossing landslide in longitudinal direction,the pipeline section at left side of landslide toe,the bend nearby landslide toe,the pipeline section nearby slide surface and pipeline section nearby landslide top,4 locations in all,have stress extreme points,and the Internal pressure,as well as temperature difference has no influence on pipeline extreme points.Under the condition of pipeline crossing landslide in transverse direction,going through the lower location of landslide has more advantages,and 2 locations of the pipeline have extreme points in all,which are distributed in the interface between landslide body and the stable body respectively,and the lower pressure pipeline,as well as the high temperature difference pipeline is more easily influenced by landslide displacements.The pipeline applied on discrete displacements can reflect the extreme stress in specific sections caused by soil shear action,which are more coincident with the law of the landslide and the analysis conclusion can make the pipeline safer.Anti-sliding pile is a kind of pile used to penetrate sliding surface from landslid mass to stable base for shallow landslide treatment.Active pressure in front of the pile and passive earth pressure behind the pile can not vary with pile diameter.With the increase of the pile diameter,the maximum shear stress and bending moment increase gradually.When the pile diameter increases to a certain value,the distribution of shear stress and bending moment no longer increases with the increase of pile diameter,and tends to be eventually stable.With the increase of the anti-slide pile diameter,the displacement at each point of the pile body gradually decreases,and the safety factor of slope body gradually increases,and finally tends to a constant value.When the anti-slide pile is arranged in the longitudinal position of the slope,it should be as close as possible to the middle position of the slope,and the transverse distance of the slope can be determined according to the requirements of the safety factor of slope stability.