Research On Friction Angle Play Of Sandy Soil Retaining Wall Based On Discrete Element Method

Retaining wall is an important structure in the field of civil engineering.A lot of earth pressure monitoring data show that the earth pressure of retaining wall is related to the displacement of wall.The non-ultimate earth pressure method considering the influence of wall displacement is developed on the basis of the traditional ultimate earth pressure analysis method.The key is how to define the relationship between the displacement of retaining wall and the extent of friction angle.However,there are few experimental research results on friction angle play,and there is no unified conclusion on the initial value,trend and limit of friction angle play.Therefore,this paper adopts numerical analysis method to study the play of friction angle with wall displacement.Firstly,the model of sandy soil retaining wall and backfill was established,and the feasibility of the test scheme and the reliability of the model results were verified by numerical test.Then,the trend of internal and external friction angle with the increase of wall displacement under different wall-movement modes is deeply analyzed,and the characteristics of internal and external friction angle under different displacement modes are summarized.The function model describing the external friction angle is selected by comparison.In the translational displacement mode,the play value of friction angle under different combinations of internal and external friction angles was further discussed,and the "play limit" of external friction angle was obtained,and the functional relationship between the "play limit" of external friction angle and different combinations of wall and soil materials was established.The following conclusions were obtained finally.On the one hand,under different retaining wall displacement modes,the internal and external friction angles play nonlinearly with the increase of wall displacement.The full play of external friction angle is generally earlier than that of internal friction angle.The wall displacement needed for the full play of the external friction angle is approximately equal to 1/3 of the wall displacement needed for the full play of the internal friction angle;The passive displacement of the wall is almost 10 times of the active displacement of the wall when the external friction angle is fully developed.Hyperbolic model can be used to describe the nonlinear trend of external friction angle under different displacement modes.On the other hand,there exists a "play limit" for the play value of the external friction angle,which is related to the value of the internal and external friction angle.When δ/φ is small,the external friction angle can be fully played at the whole height of retaining wall with the increase of wall displacement,while with the increase of δ/φ,the external friction angle of the bottom wall is difficult to fully play,and this incomplete trend gradually extends upward from the bottom of the retaining wall,resulting in the overall external friction angle of the retaining wall cannot fully play.There is a linear relationship between the limit of external friction angle and the ratio of the parameter δ/φ.