Research On Calculating Methods Of Active Earth Pressure On Retaining Wall Under Various Movement Modes

The determination of the magnitude and distribution of earth pressure against rigid retaining wall is significant in the design of civil engineering. Classical earth pressure theories such as Coulomb and Rankine earth pressure theory have been widely used to design the retaining wall because they are simple and reflect the mechanical concepts clearly. But the classical theories are only valid when the backfill of translation wall reaches the limiting condition, and assume the earth pressure distribution to be hydrostatic. While the retaining walls in service usually have some restrains and may move different from translation. The measured earth pressures on retaining wall are mostly non-linear. And in Coulomb's theory, the resultant earth pressures are obtained by the force equilibrium of sliding soil while the soil stress state is non-considered; In Rankin's theory, the earth pressures are obtained by the stress limiting equilibrium of sliding soil but the wall friction is non-considered. So, it's necessary to propose methods for evaluating earth pressure considering the wall movement modes, and it's vital for deciding the rationality and economy of the retaining wall design.The retaining wall moves from the backfill, the wall movement modes includes three kinds of basic modes-Translation (T), Rotation about base (RB), Rotation about top (RT). The objection of the thesis is the rigid retaining wall whose back is vertical and the wall subjects to move outward and away from the backfill in different modes, the stress state of the three wall movement modes and earth pressure against retaining wall are studied in-depth. The main original work is as follows:1. As for the Translation(T) mode: On the basis of coulomb's concept that the earth pressure against the back of a retaining wall is due to the thrust exerted by a sliding wedge; the basic analysis equation are set up by considering the equilibrium of the forces on an thin-layer element of the wedge. By using the equilibrium equation of the moments on the whole wedge, the lateral coefficient of earth pressure, the earth pressure distribution along the wall back are obtained.2. As for Rotation about base(RB), Rotation about top(RT) modes: Under the impact of the friction angle between wall and soil, the classic theory of the active earth pressure which acts on rigid wall is short of considering change of stress state about soil behind wall, the shear stress and deflection of the principal stress. In order to eliminate the calculation inaccuracy, the relationship between the friction angle and the inclination of the sliding plane in soil is considered. The lateral coefficient is calculated for different friction angle of soil and friction angle between wall-surface and soil based on the analysis about minor principal stress of soil arching elements to study the vertical stress and shear stress, the earth pressure distribution along the wall back are obtained.3. Under Translation, Rotation about base, Rotation about top modes, the effects of the internal frictional angle of backfill and the frictional angle between the wall and the backfill on the lateral coefficient of earth pressure, the earth pressure distribution along the wall are investigated. The proposed method was compared with some experimental data. It is demonstrated that the calculating results by this thesis's method better safety and agreement with those of the experiment than those by Coulomb's theory.The proposed methods of earth pressure calculation considered the wall movement mode. They can calculate the earth pressure of each movement modes, and they'can avoid getting lower overturning moment using Coulomb's solution that will lead to decrease the safety of the structures in design. So, the proposed methods can make the design of the retaining wall safer and more reasonable.