Passive earth pressure of vegetation rooted soils based on limit analysis and quasi-static approach

Although it has been recognized that vegetation roots have a positive effect on the stability of geotechnical structures, few quantitative studies have been performed on the effects of vegetation roots on earth pressures. In this paper, based on the upper bound limit analysis theory and quasi-static method, a new method for calculating the seismic passive earth pressure of vegetation rooted soils is proposed, which considers both the hydrological and mechanical effects of vegetation roots on the passive earth pressure. The proposed method is validated by some existing solutions. The effects of root parameters of shrubs (root transpiration rate, root tensile strength, and root depth), angle of the soil slope surface with the horizontal, and wall interface friction angle on the seismic passive earth pressure coefficient are also investigated. The results show that the passive earth pressure coefficient increases with the increase of root transpiration rate, root tensile strength, root depth, angle of the soil slope surface with the horizontal, and wall interface friction angle. Compared with the mechanical effect, the hydrological effect of vegetation roots on the passive earth pressure coefficient is more obvious. The effects of root parameters on the passive earth pressure ranked in descending order of sensitivity are root transpiration rate, root tensile strength, and root depth. In addition, the effect of vegetation roots on the passive earth pressure becomes more significant with the increase of internal friction angle. The proposed method can provide a reference for the local reinforcement of multi-stage slopes with vegetation.