A Study of Soil Water Movement and Root System for Unsaturated Slope Stability

This research established a partially saturated vegetated slope stability model combined the transportation of soil water content and root model. The paper discussed the actual benefits of the root element of the vegetation offered to the slope stability under different environment and integrated the mechanism of biomechanics, environmental, and engineering properly. In the methods of slope stability, we modified the slice method of infinite slope, Bishop’s modified method and Janbu’s simplified method. In the transportation of soil water content, the hysteresis effect is considered in the simulator. Besides, the root system of the vegetated element in this study is based on “Relations of Root System Mechanics and Slope Stability” (Wu, 1990) in which investigated root system mechanics of Taiwania cryptomerio ides and Trema orientalis (L.) Blume. Finally, the present model in this research calculated the safety coefficients of the different destruction surface in accordance with different soil water content conditions and the kinds of vegetation.he results indicated that different distributions of soil water content and the kinds of vegetation would change the safety coefficient apparently regardless of the slope gradient and the patterns of destruction surface. Therefore, the engineers should consider the transportation of soil water content and the vegetated elements when using the traditional analysis methods of slope stability. The root model of Taiwania cryptomerio ides and Trema orientalis (L.) Blume had no remarkable benefits to deeper destruction surface, but raised the safety coefficient of shallow destruction surface obviously. On the contrary, the weight of vegetative body reduced the safety coefficient of deeper destruction surface. The root system of Trema orientalis (L.) Blume is better than Taiwania cryptomerio ides in the shallow slope stabilization. The simulative results of different vegetative arrangements also showed that the planting intervals are sparser and the benefits offered to the slope stabilization are more unapparent. On the other way, the planting intervals are too close to grow normally, and the vegetation increases the loading of the slope. Besides, decreasing the soil water content of the slope or cutting down the slope gradient are effective strategy to raise the stabilization of the deeper destruction surface. Utilizing the suitable planting intervals to increase the root amount of the unit area can enhance the slope stability effectively. In conclusion, not all kinds of vegetation are suitable for some particular slopes in the design of the ecological engineering. Detailed researches and analysis are required to identify the suitable ecological engineering for a particular slope.