Study On Earth Pressures Considering Retaining Wall Deformation And Limited Soils

The classical Coulomb and Rankine earth pressure theory are widely used in the calculation of retaining wall. However, these theories are based on some hypotheses, and some practical projects can not accord with them. One of the hypotheses is that the movement of the rigid retaining wall is translation, which is probably different from the actual complicated movement mode of retaining wall; and the other hypothesis is the soil near the wall must be a semi-infinite body, that is inconsistent with some situations in which the width of the backfill is limited, such as the retaining wall adjacent to an exsiting basement, and narrow excavation etc. It is inappropriate to calculate the earth pressure in these cases using the classical pressure theories. This paper focuses on numerical and theoretical studies on the earth pressures considering the deformation of retaining wall and the limitation of soils.1. Based on the experimental and numerical results, a new model for determining active earth pressure against rigid retaining walls is proposed, which has considered the movement mode of the wall. The formulae of the coefficients of the resultant active pressures with different displacements, the unit active pressures and the heights of points of application of pressures are obtained. The comparisons between other theoretical and experimental results show that the proposed equations can predict the earth pressure on the wall satisfactorily.2. According to the same consideration of rigid retaining walls, a new model for determining active earth pressure of flexible retaining walls considering the effect of wall deformation is proposed. The formulae of the coefficients of the resultant active pressures with any displacements, the unit active pressures and the heights of points of application of pressures are obtained. The comparisons among theoretical, previous and experimental values show that the proposed model is more accordant with the experimental data.3. A FEM numerical model for retaining wall in narrow excavations is presented. The slip surfaces in the soils at passive limiting state with different widths of soils when the walls translate are investigated. Based on the concept of Coulomb sliding soil wedge, a new theoretical model for determining passive earth pressures against translating rigid retaining walls in narrow excavations is proposed. The formulae of the inclination angles of slip surfaces and coefficients of the resultant passive pressures are obtained. Then the horizontal differential element method is introduced and the unit passive pressures and the points of application of the resultant earth pressures are proposed. The factors that influence the inclination angle of slip surface under this circumstance are studied in detail. The comparisons between theoretical and numerical values show that the proposed equations satisfactorily predict the earth pressures on the wall.4. The futher computational formulae on earth pressures considering the effect of the deformation of retaining wall and adjacent exsiting basement are obtained. Then the 3D FEM program for analysis retaining structure in excavation by Guo(2006) is modified to consider the effects of the deformation of flexible retaining wall and the adjacent basement. Finally, the modified program is employed to analyse the retaining structure in a excavation case in Hangzhou. The comparisons among the calculated results proposed by the modified programm, previous methods and measured data have shown the reasonableness and practicability of the program.