Model Test And Numerical Simulation Studies Of Soil-Arching Within Pile-Supported Reinforced Embankments

The pile-supported reinforced embankment is composed of embankment filling,horizontal reinforced cushion,pile caps,piles and foundation soil.It has many advantages compared with the traditional soft soil treatment method.For example,the total settlement and post-construction settlement of embankment are small,and the post-construction settlement can be controlled in a short time.The lateral deformation is easily controlled under the combined action of the pile and horizontal reinforced cushion.The bearing capacity of the pile is efficiently utilized by setting a pile cap above the pile,which also greatly enhances the engineering economy.The pilesupported reinforced embankment has been widely used at home and abroad because of the above advantages.The stress and deformation characteristics of pile-supported reinforced embankment are complex because of the interaction between the various structures.In order to improve the design specification of pile-supported reinforced embankment and better promote this method.It has great significance in theoretical and engineering practical to clarify the development and change mechanism of soil-arching effect,reveal the bearing deformation law of pile-supported reinforced embankment and carry out theoretical analysis of existing codes.In this thesis,the development and change mechanism of soil-arching effect is deeply studied based on the indoor model test,numerical simulation and the theory analysis of design specification,and the following main conclusions are drawn:(1)The result of indoor model test and numerical simulation are both indicated that the deformation characteristic is effected by many factors,such as the pile spacing,the size of pile cap,the strength of subsoil,the strength of reinforcement and filling cohesion.The pile spacing,the size of pile cap and the strength of reinforcement have great impact on the deformation of embankment,and the cohesion of filling has little impact on it.We can know from the result of indoor model test that the differential settlement of pile-subsoil changes in stages with the increase of embankment filling height.the differential settlement of pile-subsoil increases linearly in the early stage of embankment filling,and then the development of pile-subsoil differential settlement undergoes a deceleration growth stage and a stable stage in turn.(2)The stress distribution characteristic of embankment interior and embankment bottom has been researched by indoor model test and numerical simulation.The shape of the vertical stress curve is ’ Z ’ in the center of the embankment,and the pile spacing has a great influence on the height of the maximum vertical stress at the center of the embankment,and the filling cohesion and the strength of the reinforcement have little effect on it.The stress trace has obvious deflection,which is the result of the soil arching and the membrane effect.The soil pressure above the pile cap increases,and the soil pressure above the subsoil decrease,with the increase of the filling cohesion and the strength of reinforcement.There is similarly change trend of soil pressure above the pile cap,but the change trend of soil pressure above the subsoil between piles is different,with the increase of pile spacing.(3)The pile-subsoil stress ration and the load sharing ration of pile have been adopted by the indoor model test and numerical simulation.The parametric study of the two indexes shows that two indexes will be increase with the increase of filling cohesion,the strength of reinforcement and the size of cap,and two indexes will be decrease with the increase of the subsoil strength and the pile spacing.The research results’ consistency of the above different indicators verifies the feasibility of finite element simulation once again.(4)The development and evaluation and the final shape of soil arching have been analyzed by finite element software.It takes about 1% of the relative displacement to form the complete soil-arching effect,and the relative height of embankment ash≥-0.5)(is required for the soil-arching effect to undergo the complete development stage.In addition,the height of complete soil arching the same as the plane of equal settlement.The height of the plane soil arching and the threedimensional soil arching are respectively about)(0.1 as-and)(4.1 as-,which is mainly controlled by the pile spacing and the size of cap.(5)The finite element result has been compared with the theoretical calculation result.The result of comparative analysis shows that the EBGEO-2010 and BS8006-H&R can reasonably predict the load sharing ration of pile.The calculation error of EBGEO-2010 is constantly small at different filling height.The calculation errors of the other standard are large under low embankment conditions,but the calculation errors decrease with the increase of embankment height.The calculation results of national codes decrease with the increase of pile spacing and increase with the increase of pile caps’ size.