Axi-symmetric active earth pressure for layered backfills obtained by the slip line method

The axi-symmetric active earth pressure for layered backfills was investigated using the slip line method. Due to different soil properties, the interfaces of the soil layers were considered as discontinuity surface. Accordingly, the change of the major principal direction was obtained and a new computation scheme was proposed to deal with the discontinuity in the calculation, finally the slip line method was extended to layered backfills. Results indicate that, the major principal direction, as well as the earth pressure, has a finite jump on passing the soil interfaces. The magnitude of the jump depends on the soil properties mainly. Generally, the active earth pressure when a strong layer is overlying a weak layer is much larger than that when the weak layer is lying on the strong layer. The present solution can be reduced to plane strain case and it has been compared with Rankine's and Coulomb's results, and a good agreement is observed.