Modified Computational Method For Active Earth Pressure Against Rigid Retaining Wall

The classical earth pressure theories such as Coulomb's and Rankine's earth pressure theories are wildly used to calculate the earth pressure, because it's a simple method and the results can reflect the mechanical concepts clearly. But the two assumptions of the classical earth pressure theories are quite rigid, and there are some shortages in the practical application. The two classical theories are all based on the soil behind the retaining wall that arrives at the limiting equilibrium condition. However the soil may under the non-limiting equilibrium condition when it's in the working status. Rankine's earth pressure theory points that the distribution of the earth pressure is linear along the back wall. And Coulomb's theory only can obtain the resultant force of earth pressure according to the static equilibrium of the sliding wedge from the back wall, and it assumes that the distribution is also linear along the wall height. But these aren't match with the practical situations. A lot of model tests and field tests have been proved that the distribution of earth pressure along the wall height usually to be non-linear rather than to be all linear. So, to calculate the magnitude of the earth pressure accurately, it's necessary to combine the practice with the method that considers the wall movement modes and the wall movement values, and it also can provide some guidance for the design of the retaining wall.The thesis is based on the study of the asymptotic rupture mechanism in the soil, when the retaining wall moves away from the soil back wall which we can call it the active state. And it contains three basic movement modes named Translation, Rotation about the top and Rotation about the base in this state. Then, respectively establish the relationship between the internal friction angles and the displacements under the non-limiting state about the three modes. The results reflect that the internal friction angles play along with the development of the wall movement progressively. According to the static equilibrium of the sliding wedge, it gets the basic calculation formulation of active earth pressure, and combining with the relationship that we have been made between the internal friction angles and the wall displacements. Finally, we obtain a method of the active earth pressure about the three modes under the non-limiting active state. It considers the effects about the wall movement modes and the wall movement values on the active earth pressure. Comparing the calculated results with the observations from the model tests, it shows that the value of theoretical computation is in good agreement with the measured experimental values, and it confirms the rationality of the method.The mobilization of the shearing resistance in the soil is a progressive process. In order to predict the distribution and the magnitude of the earth pressure precisely and provide some guidance for the practice, it is necessary to know the relationship between the shearing resistance in the soil and the wall displacement. The calculation method of earth pressure is proposed here that considers the effects of the wall movement modes and the wall movement values on the mobilization of shearing resistance in the soil, it can be used for calculating the distribution and magnitude of the active earth pressure under the non-limiting equilibrium condition. Comparing with the classical earth pressure theories, this method can predict the distribution and the magnitude of earth pressure more precisely and provide more reliable data for the design of the retaining walls than the classical ones.