Water Contension Variational Properties And Environmental Effects Of Reconstructed Soil Filled With Coal Gangue

There are many environmental problems from coal mining and coal combustion, the arable land loss and regional ecological environment destruction for a large area surface subsidence, the environmental pollution of atmosphere, water and soil through dust and leachate from solid waste, and so on. Furthermore, a great quantity of lands are occupied by the coal-series concomitants and coal combustion residues. Some engineering measures in coal mining areas were applied in response to the challenge of these environmental problems to sustainable development, that were the land reclamation and ecological environment restoration by reconstructed soil profiles filled with the solid waste. One of the important filling matrix was coal gangue. There exist significant differences in physical properties and the condition and migration of the water, nutrient,solute between the reconstructed soil and the natural agriculture soil.This article is based on field investigation, pot experiment, soil column experiment and laboratory analysis of parameters test. It studied coal gangue resource characteristics of Huaibei and water infiltration and nutrient migration of reconstructed soil with coal gangue and established the concept model of moisture migration.(1) It conducted further study on the composition and mineral rock structure of coal gangue in Linhuan, Xutuan, Zhuzhuang, Qinan, Taoyuan and the forth.The result shows that the five kinds of coal gangue which were analyzed have similar mineral composition, and the mineral gives priority to clay minerals and quartz. Clay mineral in washing gangue of Linhuan is pretty high.(2) Soil column experiment was used for discussing the vertical moving up characteristics of water in reconstructed soil, and establish the model of quadric surface response function to simulate the regulation of the relationship of capillary water height with the content of fine particles, gangue layer of bulk density and mudstone content. With the given conditions level of underground water, if we do not consider the influence of the surface evaporation, the vertical moving height of coal gangue moisture can be described by the quadric response model. Between model calculated value and measured value, r=0.777**, RMSE=3.5319,EF=0.5607.(3)By analyzing the heavy metal content and the environment effect of coal gangue reconstructed soil and its leachate, we can see that coal gangue exist certain impacts on heavy metals content change of reconstructed soil, in which the content variation of As element is the largest, followed by Cd element, and the variation of Cu, Zn,Cr elements are fairly, and the change and migration of Pb and Hg in the soil is small.Meanwhile, the comprehensive pollution dgree of heavy metal in coal gangue reconstructed soil is "clean". The single pollution index of Cd have been in the "light pollution", and the rest are in the "clean" level. In the leachate of reconstructed soil, the As, Cu and Pb content order of magnitude (0.00) is quite fairly and the Cd,Cr content order of magnitude (0.000) is also in accordance. The largest content in the order of magnitude(0.00) is Zn element, and the least is Hg elemen(0.0000). All the heavy metal content won’t produce harm.(4) In the Infiltration experiments, change of profile moisture content with time was connected with reclamation matrix, reconstructed soil infiltration rate, the initial water content and relative density of reconstructed soil. Soil water content of fine particle was the closest to the saturated moisture content, because of its high content of fine particle and nearest to the soil grading. In the experiments of evaporation, Reconstructed soil moisture content were decreased with the increase of evaporation days as four different ways of land reclamation, profile moisture content of topsoil of washing gangue column had the minimum change with time. On the contrary, profile moisture content of topsoil of coarse particle column had the maximum change with time. At last, coarse particle column had the lowest water content, because of too much large particles in underlying and low Water-holding capacity.(5) Setting up different models of infiltration rate with time:Washing gangue column can be expressed as infiltration model: i(t)=0.05+0.11e-0.0015tUniform grain column can be expressed as infiltration model: i(t)=0.75t-0.5+0.06Fine particle column can be expressed as infiltration model: i(t)=0.6t-0.5+0.02Coarse particle column can be expressed as infiltration model: i(t)=0.04+0.1e-0.0017tAccording to four types of models, using monthly rainfall and evaporation of Huaibei city in2011and2012. Taking use of Hydraus-1D software to simulate characteristics of water balance reconstructed soil. At the early stage of reconstruction, the water content of topsoil charged not very seriously under natural rainfall and evaporation. Water content of reconstructed soil was between the wilting coefficient and field moisture that plant can meet the demand of growth.