investigation of soil active wedge angle with linear matric suction distribution below the footing

In this paper, a theoretical approach is established to determine the active wedge angle of unsaturated soils, based on the limit equilibrium method, while matric suction varies linearly with respect to depth. in the previous researches, constant suction distribution profile within the soil has been pointed out, however, generally linear and nonlinear suction profiles develop above the ground water table. the range of suction value covers transition zone and residual zone of unsaturation. sensitivity of the proposed model, with respect to different parameters, shows that the value of active wedge angle is more dependent on the internal friction angle, in comparison to other properties. therefore, instead of a complex relation, simple equation can be used. the results show that the active wedge angle for unsaturated soils is equal to $$frac{pi }{6} + frac{7}{8}phi$$. comparisons between the presented model and experimental data show that, for some values of internal friction angle, the active wedge angle in unsaturated state is close to saturated state.