Experimental Study On Stratum Reconstruction Of Dump Soil In Open-pit Coal Mine

Surface mining inevitably will destroy local land with the self-sustaining and selfrepairing capabilities of ecosystems lost,which brings great inconvenience to the reclamation work in the subsequent mining area,especially for the dumping site of earth and rock piles.The incompatibility of the size of the bulk body causes the internal pores of the dumping site to be large and connected up and down,and the shallow surface water is quickly infiltrated,so that it is very difficult for plants to absorb and grow.Therefore,studying the stratum reconstruction to improve the water retention rate of the dumping site is of great significance for the ecological reconstruction of the mining area.Based on the soil remodeling technology in the “Key Technologies of Mining and Recycling and Large-scale Reconstruction of Large Coal-fired Power Bases”,this paper takes the Baorixile Open-pit Coal Mine as the research object,comprehensively uses laboratory tests,numerical model simulation and other methods.A systematic study of the soil sequence model was carried out.Based on the existence of water in geotechnical soil and the influencing factors of soil water holding capacity,the water holding capacity of sands with different densities was tested.The variation of field water holding capacity with the dry density of sand was obtained.PFC software was used to simulate the process of the change of mesostructure with dry density in sandy soil,and the reason of the change of field water holding capacity with dry density was analyzed.Based on the pore water seepage channel model and the principle of water flow continuity,pore size is the biggest factor affecting water seepage,and compactness is the main factor affecting pores.The seepage of clay samples with different consolidation pressures is performed by GDS tester.Experimental studies have obtained a curve of clay permeability coefficient as a function of consolidation pressure.The above two studies have determined the physical properties of the material when the soil sequence was rebuilt.According to the greening regulations and the root depth of plant growth,the thickness of the soil in the reconstructed aquifer was determined.The SEEP/W software was used to simulate the variation of the permeability of the clay aquifer with the thickness of paving soil,and the optimum aquifer thickness was determined.According to the environment required by the experiment,a stratum reconstruction model test bed was designed in the laboratory,and a soil column model with soil sequence was constructed.The controllable precipitation intensity device was used to simulate the penetration of different precipitation strength soil layers,and single layer of sand aquifer was established as a control for comparative analysis.By comparing the water content,surface runoff and bottom permeation in the three precipitation conditions of the two control models,it was found that the soil column with the sequence structure can better conserve water.Based on three experiments,the direction of water in soil and the factors affecting its infiltration capacity were analyzed.The law of water movement in soil with sequence structure was divided into two cases: the rainfall intensity is less than the saturated permeability coefficient of upper soil and the rainfall intensity is greater than the saturated permeability coefficient of soil.The law shows that the reconstructed aquifer can keep water well regardless of precipitation intensity,which indicates that it is feasible to reconstruct the soil sequence of the open pit dump,and it is also very effective to improve the reclamation efficiency.