Nonlinear description of active earth pressure for finite backfill based on principal stress trajectory method subjected to steady unsaturated seepage

To simplify calculations, soil cohesion, horizontal shear stress, and unsaturated properties have usually been neglected in previous earth pressure analytical methods. This negligence has certain theoretical flaws and does not conform to the actual situation. Especially for finite backfill, which often occurs, it is worth continuing to expand research in this field to seek a more rigorous solution. This work presents an analytical framework for estimating the active earth pressure of finite backfill on inclined retaining walls under steady unsaturated seepage conditions. The extended Mohr-Coulomb failure criterion expresses soil shear strength, and a unified effective stress method considering the suction stress is adopted. For a classic failure model, a calculation method using curved differential elements is established based on the principal stress trajectory. The proposed method fully considers soil cohesion, arching effect, and unsaturated properties. Relative to the existing test and theo-retical results, the rationality of this method is verified. The sensitivities of relevant parameters are discussed based on different assumed soil types. The results show that seepage significantly affects the lateral earth pressure. The earth pressure distributions vary greatly under different unsaturated types for various soils. The results can provide a reference for the selection of engineering backfill.