Evolution Process Of Soil Arching Effect Of Pile-supported Embankment And Its Engineering Application

Pile-supported embankments(PSEs)have been widely used in highways and highspeed railways.Under the upper load and the self-weight of fills,the difference in stiffness between the pile and the subsoil will cause the differential settlement between fills over the pile and over the subsoil,resulting in relative movement between the two parts.However,due to the limitation of the relative motion trend of the shear stress ? on the relative motion interface,part of the load is transmitted from the subsoil to the piles.Therefore,piles bear most of the embankment load.This phenomenon of stress transmission is called the “soil arching effect”.Considering that it is difficult to observe the evolution process of soil arching by conventional means,most existing researches about the soil arching effect have remained at the macro level,and the evolution process of soil arching is neglected in the calculation and analysis.In fact,the soil arching effect will gradually change as the differential settlement of piles-subsoil increases.In recent years,due to the rapid development of discrete element method and computer technology,more attention has been paid to the study of the evolution of soil arching effect,but the theoretical calculations considering the evolution process of soil arches are still limited.Therefore,based on existing literatures,this study analyzes the evolution process of soil-arching effect of PSEs by PFC(Particle flow code)and analyzes the theoretical results based on the DEM(Discrete element method)modellings.The major tasks include:Firstly,a set of corresponding DEM modellings are established based on the double-door laboratory proposed by the predecessors.The stress distribution and force chain distribution as well as the displacement contours of different fill coverage ratio H/B and differential settlements between piles and soils ? are observed.It is found that during the evolution of soil arching,the stress reduction ratio curves show a trend of decreasing first and then increasing;the stress acting on the top of the middle pile-cap is obviously higher than the top of the marginal pile-caps,which indicates that the adjacent soil arch has obvious superposition effect.Secondly,based on the discrete element test results and the soil arching evolution models proposed by the predecessors,a soil arching evolution model is proposed according to the geometric form of sliding zone under the soil arching.And the calculation method of soil arching considering the evolution process is derived.Finally,the theoretical calculation results of this paper are compared with the model test results and engineering examples as well as some classical soil arching effects calculation methods,which further validates the feasibility of the proposed method.