| During the construction of the mountain railway,due to the limited of terrain conditions,the railway as a belt project requires a large number of supporting roads in the steep slopes.The tray-type road shoulder retaining structure has broad application prospects in steep slope roadbed retaining because of its good mechanical characteristics and strong slope-recovering ability.However,the theoretical research results and system design techniques of the road shoulder retaining structure in the steep slope area are still not mature.Through filed test and FLAC 3D numerical simulation calculation,the stress and deformation characteristics of the tray-type retaining structure and its influencing factors,the following conclusions are obtained:1.According to the research theories of the cantilever retaining wall and unloading-board retaining wall,the tray-type retaining structure is studied,and the interaction theory with the soil is discussed.2.Through field test,the wall internal force and earth pressure distribution of the pallet retaining structure before and after the work are studied: The cantilever bending moment grows along the buried depth and is parabolic,and the top bending moment is close to zero;the bending moment of the tray is firstly reduced and then increased from the end of the tray to the end of the unloading-board,and rapidly reduces to zero at the portion of the unloading-board;The vertical earth pressure on the upper surface of the tray gradually increases from the tray end to the unloading-board end,showing a trapezoidal distribution;The horizontal earth pressure on the back of the cantilever wall is triangularly distributed;It also verified the unloading effect of the unloading-board on the lower wall.The numerical simulation results show that the horizontal earth pressure on the back wall of the lower wall is increased first and then decreased by the parabola distribution.3.Through numerical simulation,the three design factors of cantilever incline angle,cantilever height and unloading-board length are used to study the sensitivity of the parameters of the tray type retaining structure.Increasing the cantilever incline angle and shortening the length of the unloading-board will increase the earth pressure at the cantilever,increase the height of the cantilever will increase the earth pressure at the bottom of the cantilever.The earth pressure of the lower wall is mainly affected by the length of the unloading-board,and the length of the unloading-board is increased,the earth pressure of the lower wall will generally reduce,however,as the length of the unloading-board increases,the reduction decreases,indicating that the unloading effect of the unloading-board has a certain marginal effect;Increasing the height of the cantilever and shortening the length of the unloading-board will increase the vertical earth pressure on the upper surface of the tray.4.Based on the Coulomb earth pressure theory,according to the structural characteristics,combined with the field test and numerical simulation results,the theoretical calculation correction coefficient adapted to different design parameters is proposed.5.Due to the unloading effect,the soil on the top of the unloading-board has a large difference in the stress state,and the plastic deformation is large.When the length of the unloading plate is too short,the plastic deformation zone of the soil above the end of the unloading plate will increase rapidly.Considering that the subgrade structure is located on a steep slope,the catchment area is large and shear damage is likely to occur.Drainage measures should be taken to prevent surface water from seeping in. |
