Study On The Influence Of Permeability Safety Of Embankment When Pipeline Crossing River

Pipeline transportation,one of the five important transportation industries,which plays an important role in transport water,petroleum,natural gas and so on.It is inevitable to meet the situation that the pipeline crossing rivers during the long distance construction of the pipeline.As a result,the stability of the river embankment will be affected by the construction of the river-crossing pipeline.In recent years,the process of the urbanization construction in Hunan Province has accelerated,so the number of the river-crossing pipeline project has greatly increased.The river-crossing pipeline will affect the safety of the original hydraulic engineering definitely,(such as embankments and rivers).Because the seepage field of the embankment would be changed when the river-crossing pipeline crossed the embankment,and then the stability of seepage or stability against sliding will be endangered.Domestic research mainly focuses on the calculation analysis of specific river-crossing pipeline currently.But the research focuses on the general study of the river-crossing pipeline are seldom studied by scholars,such as the burial depth of pipeline,and the position of river-crossing pipeline.In this paper,the method of numerical simulation was adopted to research this issue.Firstly,the finite element method was used to analysis how the burial depth of pipeline,the position of river-crossing pipeline,and the permeability coefficient of the stratum affect the safety of the embankment.Secondly,the influence on the embankment which construction method results was considered in this study.The main research content and conclusions are listed below.(1)The burial depth of the pipeline had no apparent influence on the seepage gradient.But the position of pipeline crossing river,and the permeability coefficient of the stratum has greatly influenced the seepage gradient.The further the position of pipeline crossing river,or the smaller the permeability coefficient of the stratum,the smaller the maximum seepage gradient would be.(2)It would be better to choose a stratum with small permeability coefficient for pipeline to cross the river.If it is impossible to avoid the stratum which may occur water leak,it must make sure that the permeability coefficient of the upside stratum small than embankment's.Besides,the position of river-crossing pipeline should be located far from embankment,it would be better arranged 70 meters away from the landside of embankment,no less than 50 m at least.(3)The maximum seepage gradient was prone to show in the areas which two kinds of materials with different permeability coefficient contacted,such as the intersection between the unearthed point of pipeline and stratum,and the junction of embankment toe and foundation,so the seepage control measures must be taken accordingly to make sure that the safety of embankment.(4)The position of river-crossing pipeline must be determined by the calculation of the seepage before the construction of river-crossing pipeline.It is better to do some experiment use numerical simulation.Different degrees of construction have a great influence on seepage gradient.The greater the degree of construction disturbance,the higher of the seepage gradient.And the large seepage gradient will come close to the landside of embankment,where may be prone to occur seepage failure.The construction disturbance will have a great influence on the subsidence of embankment.And it would be easily cause uneven settlement of embankment.The location of the maximum settlement is in the middle of the bottom of embankment.The construction of the river-crossing pipeline has little influence on the stress of the embankment.The stress of the embankment on the landside was larger than waterside.The place of the larger stress used to be the location of the big seepage gradient and subsidence.