Study On Ecological Restoration And Stability Of Different Types Of Steep Engineering Slopes

A large number of high and steep exposed slopes are caused by long-term mining and engineering construction,which leads to the destruction of original vegetation and land,and also causes problems such as soil erosion,soil erosion,ecosystem stability reduction,etc..When heavy rainfall occurs,it is easy to cause geological disasters such as landslide and debris flow.At present,slope ecological engineering technology is widely used to manage various exposed slopes,which can achieve the comprehensive benefits such as slope protection,vegetation reconstruction,soil and water conservation and sustainable development of ecological system.However,in the ecological management of mine slopes in Shanxi Province,due to the limitations of environmental conditions such as less annual precipitation,water shortage,loose loess structure,strong collapsibility and so on,there are problems such as vegetation degradation,single community species,artificial soil collapse,wire mesh exposure and fracture in the slope restored by using the technology of external-soil spray seeding.There are obvious differences in ecological restoration effect among different types of slopes,even which have the same construction period and environmental conditions.Therefore,whether the different slope types will affect the vegetation ecological restoration and stability of the slope is a very noteworthy issue.Therefore,based on the combination of field investigation,in-situ test and laboratory test,this paper explores the engineering overview,vegetation succession characteristics,artificial soil characteristics and root soil mechanical interaction(pullout and shear strength)of different types of engineering slopes after 5 years of ecological restoration.This study can provide technical reference and scientific basis for the effective application of ecological restoration engineering of mine exposed slope and the restoration of mine degraded ecosystem in Shanxi Province.The main research results and conclusions are as follows:1.Vegetation restoration characteristics of Engineering SlopeThe vegetation type of slope is herbaceous community,and Artemisia is the dominant species of slope plant community.The trend of vegetation coverage of different types of engineering slope is: Rock slope < Soil slope< Mixed slope;the trend of aboveground biomass is:Rock slope < Mixed slope < Soil slope.The trends of Margalef index and Shannon-Wiener index are: Soil slope < Rock slope < Mixed slope.The trend of Simpson index is:rock slope > mixed slope > soil slope.2.Artificial soil characteristics of Engineering SlopeThe results of bulk density and total porosity of artificial soil in different engineering slopes indicate that the rock slope has low bulk density and large porosity.The artificial soil moisture content of different engineering slopes demonstrate that the soil moisture content of the artificial soil is about 5% in natural conditions without rainfall.On the whole,the nutrient content of artificial soil in different types of engineering slopes is significantly higher than that of the uncovered soil slope(OS).Variance analysis of two-way ANOVA,there was no significant effect of slope position on the distribution of artificial soil nutrients(P > 0.05),vegetation coverage had a significant effect on the distribution of nutrients(P < 0.05),and soil p H was not significantly affected by slope position(P > 0.05),but the interaction of slope type and vegetation,and slope type had a significant effect on soil p H(P < 0.05).The variation degree of available phosphorus is the largest(110%),which is strong variation.The variation degree of nutrients in rock slope is higher than that in soil slope and mixed slope.3.Mechanical anchorage characteristics of roots and stability of Engineering SlopePlant pullout resistance and root-soil complex shear strength are important indexes to evaluate the reinforcement effect of vegetation on slope stability,which are of great significance to study mechanical effect of root system on slope stabilization and slope stability.In this study,in-situ pull-out tests were carried out on the representative dominant plant asArtemisia annua.The results showed that the pull-out resistance of rock slope was less than that of soil slope and mixed slope,while the pull-out resistance of soil slope and mixed slope had little difference,and the size of pull-out resistance was positively correlated with the root biomass of plant(P < 0.05).By the direct shear test of root-soil complex and rootless soil specimens with different water content gradients in rock slope,it is found that the shear strength of artificial soil increased,cohesion(c)increased and internal friction angle(?)decreased due to the existence of root system.The shear strength increases with the increase of the vertical pressure,the cohesion(c)increased and the internal friction angle(?)decreased.In this study,the shear strength of the sample decreases with the increase of water content gradient,and the decreasing range shows a decreasing trend,and the changing trend of internal friction angle is inconsistent.The tendency of cohesion of different types of slope root soil complex at 20% water content is: Soil slope < Rock slope < Mixed slope,which shows that the stability of soil slope is relatively lower under rainfall conditions,which results in the phenomenon of whole collapse of artificial soil layer of soil slope during the survey of slope engineering.In conclusion,there are obvious differences in the characteristics of ecological restoration and root mechanical anchorage between different types of engineering slopes with similar environmental conditions.The vegetation on the slope mainly forms the herbaceous community with the native plant Artemisia as the dominant species,and the species diversity and aboveground biomass of different types of project slopes are different.The structure of artificial soil in rock slope is loose and its water holding capacity is poor.The distribution of soil nutrients was affected by the vegetation cover on the slope,but the slope position did not affect the artificial soil nutrients.The mechanical anchorage characteristics of the root system of the dominant plant species on the slope indicated that the pull-out resistance of the root system of the dominant plant species on the rock slope was less than that of the soil and mixed slope.The shear strength indexcohesion of the root-soil complex of the soil slope is obviously smaller than that of the rock slope and the mixed slope.Based on our investigation of the engineering profile of the engineering slope,our research results suggest that the type of the engineering slope may affect the ecological restoration characteristics and stability of the engineering slope through the site habitat differences caused by different slope components.