| The hydrological effects of plant slopes is mainly studied on how plant roots affect the seepage of slope soil,which is an important aspect of the research on plant soil consolidation and slope protection.Most of the current studies focus on the absorption of excess water within the slope soil by plant roots after rainfall,which is excluded from the soil through transpiration of plant stems and leaves to reduce the pore water pressure of the slope soil and thus improve the stability of the slope.But at the same time,the presence of plant roots can also go to cause the phenomenon of preferential flow in the inter-rooted soil,and make part of the slope soil infiltrate more water during the rainfall,which reduces the stability of the slope.Therefore,it is of theoretical significance and practical value to study the influence of preferential flow effect on the seepage characteristics of plant slopes under rainfall conditions.Relying on the National Natural Science Foundation of China(NSFC)project,the experimental research,the theoretical research and numerical simulation analysis are combined to study the effect of preferential flow action on the stability of plant slopes under rainfall conditions.The main conclusions obtained from the thesis are as follows:(1)Through rainfall tests on outdoor slopes,it is found that the pore water pressure value within the soil of Vetiver grass plant slopes is slightly larger when continuous rainfall is 4052s compared with bare slopes of the same soil depth,and it shows a trend of first increasing and then decreasing with the increase of soil depth,reaching the maximum value at the depth of 15cm soil layer.It indicates that the presence of plant roots increases the permeability of the slope soil,resulting in the increase of water content and pore water pressure,indicating the existence of preferential flow phenomenon in the plant slope.(2)Through field dye tracing tests on Vetiver plant slopes,it was found that the degree of preferential flow development of slope soils was higher in Vetiver plant slopes with smaller planting spacing.When the rainfall increased,the degree of preferential flow development in Vetiver plant slope soils also increased.(3)Under the short-term rainfall conditions,the infiltration depth and permeability of the preferential domain in the slope of Vetiver grass plants are greater than those in the matrix domain,and the size of rainfall has little effect on the maximum infiltration depth of the slope soil.(4)By counting and staining profiles of Vetiver grass roots in Vetiver plant slope soils,it was found that the number of Vetiver grass roots and root surface area decreased with the increase of slope soil depth,and the average staining area ratio increased with the increase of the number of roots and root surface area,which were linearly correlated.(5)The stability of the slope with or without plant cover was analyzed by numerical simulation,and it was found that the safety coefficient of the bare slope without rainfall was 1.162,which was much smaller than that of the Vetiver plant slope 1.404.The safety coefficient of the Vetiver plant slope was increased by 1.21 times through the reinforcing effect of the Vetiver root.After 96h of rainfall,the pore water pressure of Vetiver plant slope was greater than that of bare slope,and the safety coefficient of Vetiver plant slope was 1.102 at this time,but the safety coefficient of bare slope decreased from 1.162 to below 1,and the slope was damaged.Under different rainfall intensity conditions,the pore water pressure of both the matrix domain and the preferential domain of the Vetiver plant slope increased with the increase of rainfall intensity and the increase of rainfall time. |
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