Experimental Study On Ecological Restoration Of Open-Pit Mine Dumps Slope In Semi-Arid Areas

Shengli open-pit mine is an important coal base in China.However,the ecological environment of this mining area has suffered serious degradation due to the exploitation of coal resources.The plant substrate is an important factor in the reconstruction and ecological restoration of dump slopes in mining areas.Therefore,this thesis improves the effect of ecological restoration of dump slopes in semi-arid mining areas under the influence of evaporation,infiltration,runoff,water and soil loss,and soil moisture on the dump slopes in order to reduce soil erosion and enable seed germination and plant growth on the slopes.Based on pot experiment,with the addition of matrix materials such as sludge,fly ash,slag,straw,and nitrogen,phosphorus,potassium were mixed to improve soil fertility.The physicochemical properties of the plant substrate,the seed germination,plant growth,the effect of the plants on the runoff and the water and soil loss were determined.The test was conducted on three different types of slopes,such as a 20° single slope(K1),a 30° single slope(K2),and a multi-layer slope(K3),with over a 24-hour interval of rainfall.The amounts of each rainfall on slopes K1,K2,and K3 were 500 ml,550 ml,and 575 ml,respectively.This rain simulation study was carried out using a high-pressure hydraulic sprayer to study the characteristics of precipitation and watering plants.The matrix materials were evenly distributed in polyethylene pots measuring 40 cm in length,30 cm in width,and 20 cm in height.Those pots were watered for one week to improve soil quality before sowing.The seeds were covered with material after sowing about 2 cm thick and then watered until saturated,and soil moisture was observed daily for proper hydration.In this experiment,five plants were selected: M.sativa,F.arundinaceae,T.aestvum,L.chinensis,and A.fruiticosa.The results of the physicochemical properties of the study showed that the electrical conductivity and p H of the plant substrate in the untreated soil(reference soil)were relatively higher when compared with other treated soils and belonged to those of an alkaline soil.Organic matter like nitrogen,phosphorus,and potassium were relatively lower compared to the treated soils,which indicates a lower content of nutrients and inhibits plant growth in the substrate.The specific content of sludge,fly ash,and slag were key factors influencing indicators such as infiltration,evaporation,p H,electrical conductivity,organic matter,and plant growth rate.With the increase in slope angle,the magnitude of soil moisture reduction for each slope type gradually decreases,the initial production time decreases,and the higher angle is favourable to the adequate infiltration of rainwater,so the amount of erosion is relatively low.Under the effect of intermittent precipitation,due to the higher water content of the surface soil,the trend of increasing soil moisture is closer.With the increase in precipitation,the initial production time decreases considerably,the time needed to reach a stable runoff decreases,the stable flow rate increases,and the water and soil loss increases.Based on the pot experiment,the potential germination of the plants and their growth indicators were determined.The results showed that during seed germination,T.aestivum was the first plant to germinate,followed by F.arundinaceae plant.Both plants had favourable germination quality,with an average germination rate of 93.33% and 88.88%,respectively.The A.fruticosa plant was the last to germinate,with an average germination rate of 16.66%.In terms of plant photosynthesis,the number of yellow leaves and ecological disturbances on the slopes were the least strong,and the number of green leaves at different levels was the greatest.Plant biomass was also determined.Based on plant growth tests,with platforms,upper slope,middle slope,and lower slopes.The relevant indicators of plant growth were determined,and the results showed that the inhibiting effect on the aerial part of plants is more significant compared to the underground part of slopes,although the coating is favourable for plant growth and the development of roots.The root lengths of T.aestivum and F.arundinaceae plants were very developed,with an average of 40.5 cm and 18.56 cm,respectively,which can play an important role in the stability of open pit mine dump slopes.The plants also intercepted rapidly falling raindrops before reaching the bottom of dump slopes,reducing erosion from rain splashes as well as runoff and loss of water and soil.These plants are favourable to the reduction of runoff,water,and soil loss and can control erosion by intercepting rainfall and stabilising the slope surface with developed root systems.In this study,the appropriate slope for the ecological restoration of these different types of slopes was slope K3,and the appropriate angle was 20°.There are 39 figures,28 tables and 83 references in this thesis.