Analysis And Application Research On The Mechanical Characteristics Of Pile Supported Retaining Wall In High Fill Slope

In high fill slope engineering,problems such as uneven settlement of foundation and settlement deformation of high fill under self-weight stress,as well as excessive deformation of retaining structure and serious stress concentration caused by landslide thrust often occur.At the same time,because the traditional gravity retaining wall is self-heavy,the bearing capacity of the foundation is higher,and the foundation needs to be excavated is deeper,so it is not applicable to the soft foundation.As a new type of retaining structure,pile-supported retaining wall structure has the characteristics of light structure and small deformation.It is mainly used to solve the contradiction of low bearing capacity of the foundation of retaining wall structure.Because the pile is embedded in the soil at a certain depth,the retaining structure as a whole can play a role in stabilizing the slope and has a good application prospect in slope engineering.At present,although the structure has been applied in other projects to a certain extent,the mechanism of action is more complex due to the existence of retaining wall,joist,pile foundation,slope and foundation soil and other structures,and the force between them and the transmission path are not clear.In view of the above problems,this paper relies on a high fill slope project in Linxia City,Gansu Province,through theoretical analysis,field tests and numerical simulation to carry out a systematic study.The main contents and conclusions of the study are as follows:(1)According to the nature of the slope and the load acting on the retaining structure and the different displacement modes of the retaining wall,combined with the active earth pressure calculation theory of the retaining wall under the limit state and the active earth pressure calculation theory of the retaining wall under the non-limit state,the active earth pressure calculation theory of the retaining wall under different displacement modes and the distribution law of the earth pressure behind the wall along the wall height are discussed.The results show that the earth pressure on the retaining wall is not linearly distributed along the height of the wall,but is related to the displacement mode of the retaining wall.When the retaining wall is in RT and RTT displacement mode,the earth pressure distribution behind the wall presents a convex curve distribution,while when the retaining wall is in RB and RBT displacement mode,the earth pressure distribution behind the wall presents a concave curve distribution.Therefore,the theoretical calculation formula should be reasonably selected according to the displacement mode of the retaining wall.(2)Combined with the design method of pile retaining wall structure in China,this paper studies the combined retaining structure of three rows of bored piles.By introducing the elastic foundation beam theory considering the interaction between the joist and the soil,the force of the joist is calculated.At the same time,considering the pile-soil interaction,the pile structure unit is regarded as the vertical distribution of elastic foundation beam,and the "m" method is used to calculate the internal force and deformation of the pile.(3)For the high fill slope project relied on in this paper,a typical section is selected,and various testing instruments are buried in the site to carry out long-term monitoring of the displacement,earth pressure behind the wall,internal force of the pile and earth pressure around the pile during and after construction of the pile-supported retaining wall composite retaining structure.The monitoring results show that the pile limits the deformation of the retaining wall,and the structure deforms together as a whole.Moreover,the force of the front and rear piles is different,and the internal force of the external piles is the largest.(4)In order to study the adaptability of different retaining forms to the high fill slope,the finite element numerical simulation software ABAQUS is used to establish the overall three-dimensional numerical analysis model of the two retaining schemes of the gravity retaining wall and the three-row bored pile combined retaining wall structure,respectively.Combined with the analytical calculation results and the field test results,the stress and deformation characteristics of the two different schemes and the combined pile-wall retaining structures under different working conditions are analyzed comprehensively.The analysis shows that the stress distribution,displacement and deformation of the combined retaining wall with three rows of bored piles are obviously better than that with gravity retaining wall alone.At the end of the paper,the effect of earthquake on the structure is considered,and the dynamic response of pile retaining wall structure under horizontal earthquake force is studied by numerical simulation,which provides some theoretical reference for the seismic design of practical engineering.