Effect of slip surface shape on active earth pressure upon retaining wall

Based on the plastic limit analysis theory, the calculation formulas of active earth pressure for retaining wall were derived at the linear and logarithmic spiral slip pattern respectively. And the features of active earth pressure between the plane slip surface and logarithmic spiral slip surface were also compared through the calculation examples. The linear slip surface is considered as a special case of the logarithmic spiral slip surface the point of resultant force of active earth pressure for linear slip surface was determined by the combination of the two calculation formulas. With the increase of slip surface curvature, the point of resultant force of active earth pressure gradually moves up, the value of active earth pressure slightly increases but there is significant increase in the moment of the wall toe. The parameters of the retaining wall were analyzed to study its influence on the point of resultant force of active earth pressure for linear slip surface. The point of resultant force moves up with the increase of the internal friction angle of backfilled soil, the inclination of the retaining wall, the inclination of backfilled soil; and it moves down with the increase of wall-soil friction angle, the ratio of cohesion and the product of wall height and soil bulk density. The result shows that the point of resultant force lies about 0.2 to 0.4 times of the wall height. The results of the study have significant references for how to select slip surface shape to calculate active earth pressure on retaining wall.