Research On Large Ground Displacement Effects On Bridge Pile Foundation Under Earthquake Liquefaction And Improvements Techniques

The large ground displacement induced by liquefaction of earthquake may result in serious damages to the life engineering such as highway , railway , bridge piles and underground lines . Since 1980s it was firstly discovered the facts of the large ground displacement of liquefaction,the research of the lateral displacement of liquefaction has become a big problem in the geotechnical engineering . Six aspects are studied in this paper.1,The rules of the large ground displacement of liquefaction and the disasters caused by the large ground displacement of liquefaction are summarized, and the mechanism and the factors which could affect the large ground displacement of liquefaction are studied comprehensively ; the latest developments and the calculation methods of the large ground displacement of liquefaction are summed up.2,Based on the tests of former researchers , this paper use FEM(finite element method )to make a comprehensive research on the lateral displacement of liquefaction mainly about : how it change under two or three layers soil when it is suffered diverse acceleration and varying height of liquefaction soils,and how the difference of the large ground displacement of liquefaction between two or three layers soil is ; when the boundaries and location of liquefaction soil is changed ,the affects are discussed ; when the liquefaction soil is local or two parts,the rules of the large ground displacement of liquefaction are also disccused.3,The disasters of bridge piles under earthquake liquefaction are summarized and the large ground displacement of liquefaction is one of the most important reasons. In case of large ground displacements ,the bridge pile destroy is induced by the additional static pressure when the liquefied soil has a very low shear strength which could not resist the soil movement .4,The methods are concluded when pile suffered the level force and the LE method based on the centrifugal model tests is recommended to calculate the maximal moment under two or three soil layers. Use the FEM to study the pile displacement and moment: the maximal moment which control the pile destroy is produced between the up liquefied soil and blow nonliquefied soil in the case of two layer soils ; the maximal moment is located in the up noliquefied soil and below nonliquefied soil in the case of three layer soils .5,Different methods of ground improvements against lateral spread and large ground displacement are concluded . the gravel column's applications in liquefied soil improvement are summarized and the problems when it is used to improve fields which have the small degree liquefied soil are brought up. the FEM method is utilized to study the gravel column depth which could resist the large ground displacement ,this paper use four different length of Columns to make research .the result is : the gravel Column should drill through the liquefied soil; when the gravel column does not drill through the liquefied soil, the whole improved soil layers have large displacement along the liquefied soil ;when the gravel Column length come up to the bottom of the liquefied soil layer, much longer gravel columns could not make the level displacement efficiently ,must enlarge the improved soils to reduce the displacement.6,30m,50m,80m width of improve fields are used to study the appropriate width to resist the large ground displacement , the results are : the displacement of the improved areas is reduced greatly when the improved width increases ;the different improved width has a width where the bridge pile is suffered small moments ; but when it is located edges of improved areas ,the bridge pile produces very large moments.