Research On The Effect Of Soils In Tidal Flat Reclamation Area On Piles

The soft soil foundation in the coastal tidal flats area after reclamation has rheological characteristic when it is under self-weight or additional load,and it will cause damage or hysteretic displacement and deformation to the artificial structures such as bridges and buildings built upon the foundation.On the one hand,the pile foundation of structures must puncture through the soft clay layer,and the gentle inclined soil and uneven geological structure will lead to deformation of soft soil.On the other hand,local loads(such as the actions of surcharge,embankment or vehicles etc.)acting on soft soil will lead to lateral rheological deformation,and it will cause lateral stress to pile foundations of artificial structures to form bending deformation.These two effects will lead to the time-dependent deformation of piles in the soft soil and maybe endanger the safety of bridge or even result in an accident.Based on a practical project,the thesis focused on the rheological characteristic of soft soil in reclamation area,and a rheological test was carried out for remolded soil and improved soil,and then time-dependent effects of rheological characteristic of soft soil on pile and anti-deformation treatments were studied by numerical simulation method.It mainly includes the following aspects.(1)After the preparation of the remolded soil and improved soil samples,a creeping test was carried out by home-made devices with multi-stage loading method,then fitting the experimental data to get creep parameters with time hardening and power-exponential function coupled creep model.Lastly constitutive model was obtained.(2)3-dimentioanl single pile of finite element mechanical analytical model was established based on a practical project with time hardening power function rule and Druker-Prager yield failure criterion coupled creep model,the time-dependent effects of gentle inclined soil on pile where there is an embankment nearby were analyzed,and the rule of time-dependent deformation of pile was obtained.(3)3-dimentioanl pile groups of finite element mechanical analytical model was established based on a practical project with viscoelastic-plastic rheological model,the time-dependent effects of surcharge on pile groups were analyzed,and both the location and the level of the surcharge was considered.(4)Based on the creep parameters fitted by the experimental data above,finite element analysis of active ground treatment for pile groups under the surcharge was employed to evaluate the effects of the width and depth of equivalent cement-soil.