Ecological Restoration Model Construction Of Engineering Accumulation With Different Soil Configurations

Engineering accumulations,where are easy to cause serious soil and water loss,poor landscape coordination and strong environmental hazards,are a byproduct of construction projects.It is necessary and urgent to conduct the ecological restoration model on engineering accumulation.To explore the characteristics of soil and water loss and construct the ecological restoration modes of engineering accumulations,a typical engineering accumulation in the dry-hot valley area and the other typical engineering accumulations in the warm and humid area were selected.According to the natural conditions and major contradictions in ecological restoration of the two typical engineering accumulations,the ecological restoration modes that based on configuration in different soil layers,investigation of native vegetation species,and selection of environment-friendly polymer materials and organic fertilizer were constructed.Then the characteristics of soil erosion on the slopes of engineering accumulations were investigated via scouring tests.1)Shrub-grassland was the main group of the dry-hot valley and the warm and humid area.Moreover,among the plant species,shrub tussock type was the largest group,accounting for 72.22%and 65.91%of the total species in the community of the dry-hot valley and the warm and humid area,respectively.Among the herbs,Poaceae,Asteraceae and Fabaceae were the main existing forms.Vegetations such as Heteropogon contortus,Phragmites australis,and Suaeda glauca showed the greatest superiority degrees in the dry-hot valley,while Medicago sativa,Avena sativa,and Robinia pseudoacacia showed the greatest superiority degrees in the warm and humid area.2)As the simulation scouring tests in the dry-hot valley progressed,an exponential decreasing trend(S=a?e^bt,P≤0.01)in soil sediment concentration was observed over time.Increasing-decreasing-stability trends for the flow velocity and flow power,while a decreasing-increasing-stability trend for the flow resistance f were observed over time.Both native grass and PAM（polyacrylamide）could effectively control soil loss and change flow characteristics by increasing the flow resistance f and decreasing the flow velocity and flow power.Additionally,PG3（PAM in application of 1 g/L and native grass）was the best in the ecological restoration modes of engineering accumulations.Compared with B5（blank）,soil sediment concentration,flow velocity and flow power decrease by 46.21%,27.69%and31.42%,respectively,and increase flow resistance f by 78.95%for PG3.3)As the simulation scouring tests in the warm and humid area progressed,different ecological restoration modes could change the sediment yield process in different levels.A sharp increasing-decreasing-stability trend for the soil sediment concentration in CK（blank）,and fluctuating decreasing-stability trends in others were observed over the tests time.Those results indicated that the initial stages of soil erosion were obviously different between CK and other ecological restoration modes.As the tests progressed,slowly increasing trends in the flow velocity and flow power were observed,while a slow decreasing trend in the flow resistance f was observed.Native vegetation could notably increase the resistance f and decrease the flow velocity and flow power.Additionally,the effects of Medicago sativa and Avena sativa in controlling soil loss and changing hydraulic properties were the best,indicating that the ecological restoration effects of measures with grass were better than measures with tree-grass.Notably,the addition of gravel to the topsoil layer was not conducive to the ecological restoration of the engineering accumulations in the warm and humid area.4)The soil configuration with laying down a dense homogeneous soil layer on the surface of the accumulation and overlaying a gravel layer is suitable for ecological restoration on engineering accumulations in dry and hot valley areas.While the soil configuration with directly overlaying a soil layer on the surface of the accumulation is suitable for ecological restoration on engineering accumulations in warm and humid areas.Moreover,under short-term ecological restoration conditions,the ecological restoration on engineering accumulations in dry and hot valley areas is suitable to use Heteropogon contortus and PAM in application of 1 g/L,and the ecological restoration on engineering accumulations in warm and humid areas is suitable to adopt yellow soil with Medicago sativa or yellow soil with Avena sativa.