Active Earth Pressure against Rigid Retaining Walls Subjected to Confined Cohesionless Soil

This study proposes a practical method for determining active earth pressure of confined cohesionless soil. A trapezoidal thrust wedge model confined by two vertical rigid retaining walls is developed to derive the governing equations of earth pressure distribution and the resultant force. The resultant force depends on the unknown incline angle of the sliding plane and must be maximized with respect to the angle. The active earth pressure can be determined once the incline angle is obtained by solving the governing equations with the finite-difference method. Based on these equations, parametric studies are conducted to investigate the effects of the confined width on the active earth pressure and the inclination of the sliding plane. As expected, the active earth pressure decreases with the confined width due to the arching effect. In contrast, the incline angle of the slip plane in the confined cohesionless soil is in close proximity to that of Coulomb’s solution. Moreover, the incline angle of the proposed solution and Coulomb’s solution are used to determine the active earth pressure, respectively. The results of the two solutions are almost equivalent. Based on these findings, a practical method is proposed, in which the incline angle of Coulomb’s solution is suggested for the derived equations to determine the active earth pressure of confined cohesionless soil. The proposed method provides satisfactory results when compared with previous studies.