Numerical Analysis Of Temperature And Stress Fields In Subgrade With Cantilever Retaining Wall In Seasonally Frozen Regions

China has a vast territory,and seasonal frozen soil area accounts for about 53% of China's area.With the continuous development of engineering construction,the roadbed diseases caused by freeze-thaw cycle in seasonal frozen soil area are getting more and more attention.In winter,the water in the embankment changes from liquid to solid ice,and the volume increases,resulting in frost heave of the embankment.In spring and summer,as the temperature rises,the ice in the embankment gradually melts.Because the upper permafrost melts while the lower layer has not melted,the water in the upper layer cannot be discharged in time,and the embankment strength decreases.When the permafrost of embankment internal melts completely,the structure of the soil changes and thaws.Yinxi line spans three provinces of Yinchuan,Gansu and Shanxi.The long distance of the line is located in a complex engineering environment.Yinchuan is located in the northwest of China.The embankment of this section is asymmetric structure,up to 6m,with l-shaped retaining wall retaining on one side and slope on the other side.This paper,by using the finite element software ANSYS to l-shaped retaining wall section of the roadbed retaining wall temperature field and stress field numerical simulation analysis of freeze,the l-shaped retaining wall embankment retaining wall temperature field distribution,low temperature under the action of embankment frost heave deformation law,back wall horizontal frost heaving force distribution,the wall stress change and take insulation board antifreeze treatment effect and the appropriate depth.The following conclusions are obtained:1.Distribution law of temperature field of l-shaped retaining wall embankment.During the freezing period,roadbed freezing in front at the side of the l-shaped retaining wall for a reverse "S" type curve,the freezing front along the embankment surface from embankment center to retaining wall on one side of the level of development,and then downward deflection along the depth direction according to certain slope development,near the heel plate at the bottom of the freeze front second turning point,then along the direction is almost parallel to the ground surface.On one side of the slope,the frozen front in the subgrade deflects downward from the center of the subgrade along the direction parallel to the subgrade to the shoulder of the road.2.Distribution law of temperature field of l-shaped retaining wall subgrade with insulation board.After the thermal insulation board is laid,the temperature isotherm of the roadbed on one side of the l-shaped retaining wall gathers near the thermal insulation board,develops horizontally from the center of the roadbed to the side of the retaining wall,develops downward along the vertical thermal insulation board when it reaches the road shoulder,deflects around the heel board,and extends in the direction parallel to the foundationsurface.Before reaching the lowest temperature,only the upper part of the horizontal insulation board has a freezing zone,and when the maximum freezing depth is reached,the lower part of the horizontal insulation board has a high-temperature negative temperature freezing zone.When the insulation board is buried at a depth of 20 cm,the frozen area is large,and when the depth is 40 cm,the frozen area is large in the upper part of the horizontal insulation board,and more cooling capacity is retained on the upper surface of the horizontal insulation board,resulting in a larger triangular frozen area in the lower part of the horizontal insulation board than when the depth is 30 cm.It is recommended that the insulation board should be buried at a depth of 30 cm.3.Vertical displacement of roadbed top surface of l-shaped retaining wall and horizontal displacement of retaining wall during freezing period.When the insulation board is not laid,the horizontal displacement distribution of the retaining wall vertical arm is a curve that decreases gradually from the cantilever end downward.When the insulation board is not laid,the vertical displacement of the roadbed top gradually decreases from the side of the slope to the center line of the roadbed,and continues to increase towards the retaining wall supporting side,and the vertical displacement of the roadbed side of the retaining wall is slightly larger than that of the side of the slope.4.During the freezing period,the vertical displacement of the roadbed top surface of the insulation board and the horizontal displacement of the retaining wall shall be set.After laying the insulation board,the distribution law is that the displacement of the cantilever end is the largest,and it decreases gradually along the wall height.At the lower part of the retaining wall,the horizontal displacement of the lateral nodes of the retaining wall increases due to the buried depth in front of the wall.After laying the insulation board,the top surface of the roadbed will not deform basically during the freezing period,and the vertical displacement is a horizontal line with little fluctuation along the roadbed surface.5.Distribution law of soil pressure and horizontal frost heave force on the back of l-shaped retaining wall.When no insulation measures are set,the distribution pattern of horizontal frost heave force on the wall back at the lowest temperature is a triangle with a smaller upper part and a larger lower part,which is similar to the distribution pattern of earth pressure.When the freezing depth is the maximum,the horizontal frost heave force on the back of the wall is distributed in the middle part,and the maximum frost heave force appears in the middle of the retaining wall.After the insulation board is laid,the horizontal frost heave force is applied on the upper wall of the horizontal insulation board at the lowest temperature,and the maximum value is reached near the buried depth of the horizontal insulation board.The lower part is the earth pressure,which is similar to the initial stress field.At the maximum freezing depth,both the upper and lower parts of the horizontal insulation board have horizontal frost heave force,which is distributed in the form of small horizontal frost heaveforce at the cantilever end.The buried depth of the horizontal insulation board gradually increases down to the maximum freezing depth,gradually decreases to the maximum freezing depth,and continues down to the earth pressure increasing along the depth.