Active and passive critical slip fields for cohesionless soils and calculation of lateral earth pressures

A new method of solving earth pressure problems is proposed in this paper w ithin the framework of the limit equilibrium approach. The concept of the c ritical slip held (CSF) is postulated: the active critical slip field (ACSF ) in the active case, and the passive critical slip field (PCSF) in the pas sive case, Based on the principle of extremum thrust force (which is theore tically consistent with the principle of optimality) in conjunction with th e method of slices, a numerical procedure is presented for the determinatio n of such fields and consequently the distribution of earth pressures on re taining walls. For simplicity at this stage, the backfill material is assum ed to be a homogeneous cohesionless soil with sloping ground surface carryi ng uniform and vertical surcharge, while the retaining wall is allowed to b e battered, and the strength of the soil may be either fully or partially m obilised, Compared,vith the rigorous method (i.e. the method of characteris tics), the proposed method is simple in principle and easily implemented in a computer program, However, it is more accurate than other approximate te chniques and agrees well with available closed-form solutions. A number of examples of ACSF and PCSF are given in this paper, and the validity and eff iciency of the proposed method are demonstrated. In addition, it is easy to extend this numerical procedure to obtain more general ACSF and PCSF accom modating non-homogeneous c, phi soils subject to complicated loading condit ions.