Abstract: Due to transpiration, the uptake of water by plant root plays a vital role in the stability of soil slope. To quantify such effect, the water uptake by four types of plant roots(uniform, triangular, exponential, and parabolic) were simulated using finite element method,and the effects of root’s geometry and depth on pore water pressure were also analyzed. Results demonstrate that with the proceeding of water uptake, shallow pore water pressure gradually decreases, while safety factor climbs, the shear strength of unsaturated soil increases, and slope stability enhances. The envelopes of pore water pressure and safety factor ratio of the four types of plant roots are basically the same as the root distribution’s shape function. The exponential root has the most superior reinforcement effect on slope because of its lowest ground surface pore water pressure and largest safety factor ratio. Given the same total root amount, the greater the root depth is, the larger the influence zone is, and the lower vegetated soil’s shear strength and smaller factor of safety increment.

Key words: water uptake by plant root, slope stability, root geometry, root depth, pore water pressure, transpiration effect