Studies Of Active Earth Pressures On Retaining Wall

Two classic theories of earth pressures are extensively used in engineering fortheir simply calculated and sharp concept. In Coulomb's theory, the resultant earthpressures are obtained by the force equilibrium of sliding soil and the soil stress state isnon-considered. In Rankin's theory, the earth pressures are obtained by the stresslimiting equilibrium of sliding soil, the wall friction is non-considered.Based on combining the idea and methods of two theories, the deficiency of theflat sliding surface and non-balance of the moment of sliding soil in Coulomb's theoryis analyzed; and the problems in the soil arching effect to calculate earth pressures areexplained by analyzing the path of minor principal stress and arch crown. Thelayer-by-layer asymptotic method is created by modifying horizontal-soil-stratummethod for considering the change of length of stratum, tilt angle, friction angle on wallsurface and sliding surface along with wall height. The calculating results indicate thatthe distribution of active earth pressures is nonlinear and the sliding surface is curved.The methods to calculate the friction angle in any height are established forconsidering that the displacement in lower wall is too small to obtain limiting stateunder rotation about the base and the displacement in upper wall is so small that thedisplacement of the adjacent soil layer is inhibited under rotation about the top.Equations to calculate the unit earth pressure, the resultant earth pressure and the pointsof application of resultant earth pressure on retaining wall are set up under translational,rotation about the base and rotation about the top. Comparison is made among theresults calculated by formula presented here and the other methods and theexperimental observations. It is demonstrated that the calculating results by this paper'smethod have better safety and agreement with those of the experimental observationsthan those by Coulomb's theory.Based the wall displacement's increasing with placement in layers, the influenceon earth pressures on retaining wall under three displacement models are analyzed. AndEquations to calculate the friction angle in any height and active earth pressures onretaining wall are build up. Comparison is made among the results calculated byformula presented here and the other methods and the experimental observations.