Stability Analysis And Bearing Capacity Characteristics For Geo-encapsulated Stone Column-supported Embankments

In this paper,the numerical model of the unit body geo-encasement stone column under two boundary conditions of displacement loading mode and embankment loading mode is established.Two simplified analytical theoretical solutions are compiled based on MATLAB.Combined with literature verification,the applicable conditions of the analytical solution are proposed through parameter analysis.At the same time,a column group model under embankment load was established and the column group settlement,internal force characteristics,embankment stability and critical column length of suspended columns under different working conditions were carried out.The specific conclusions are as follows:(1)It is obtained through two analytical solution models that the settlement,radial deformation,settlement factor,column radius and column-soil stress solved by the incremental model are slightly larger than those of the total model.And with the increase of the applied load,they all increase.It is also found that the encased of geogrid can not only restrain the increase of the column radius,but also increase the bearing ratio of the column stress.(2)The numerical models of the two cell columns show that:(1)the maximum radial deformation of the column occurs at 1.2 times the column diameter and reaches the minimum value at the column bottom.(2)The column-soil replacement rate has a higher influence on the column-soil settlement and the column-soil replacement rate as well as embankment cohesion have a higher influence on the column-soil settlement difference.The column-soil replacement rate also has a higher influence on the column-soil stress value and the reinforcement stiffness has a higher influence on the column-soil stress ratio.(3)When the column friction angle is in the range of 30° to 46° and other parameters are the same,the influence degree of the analytical solution on the settlement and the influence degree of the numerical solution on the settlement of the soil top under the embankment are both “low”influence degrees.It is simplified to the solution value of the analytical solution,that is the top settlement obtained directly by the analytical solution is consistent with the actual situation.(3)Research on column-soil settlement under the column group model:(1)The general trend of column-soil settlement under the support of ordinary stone columns and geoencasement stone columns is the same and the maximum vertical displacement occurs at a position 2～4 meters from the centerline of the embankment.As the center line increases,the column-soil settlement decreases gradually.(2)The biggest influence on column-soil settlement is the column length,followed by the column-soil replacement rate and soil cohesion;The column length and the column-soil replacement rate have a greater impact on the column-soil settlement difference,while the column and embankment friction angle have little effect on column-soil settlement and its difference.(4)Research on column-soil internal force characteristics under the column group model:(1)At a distance of 19～20 m from the embankment centerline(the toe of the embankment),the phenomenon of V/Vmax greater than 1 appears at the top of the two columns,that is the columns are sheared and damaged.(2)Increasing the replacement rate of column and soil can effectively reduce the maximum value of V/Vmax and the shear failure position of the column is gradually moved up,which can also effectively reduce the maximum axial force of the column.Increasing the column length can increase the axial force of the column and increasing the embankment the filling height is more prone to shear failure.(5)Stability study of embankment under column group model:(1)The safety factor of GESCs embankment is always higher than that of OSC and soil cohesion has the highest influence on the safety factor of embankment,followed by column length.However,the friction angle of the embankment,the cohesion of the embankment and the cohesion of the soil have a high influence on the failure mode of the embankment.The slip surface moves upward with the increase of column friction angle and column-soil replacement rate.(2)The safety factor of embankment increases with the increase of column length,column friction angle,embankment friction angle,soft soil cohesion,column-soil replacement rate and stiffness of the wrapping material.When the soil cohesion is small,the improvement is more obvious,when it exceeds 40 kPa the influence on the safety factor is negligible.