The Effects Of Compaction Resulted From Large Machineries On Soil Pore Properties In An Opencast Coal Mine Dump In Loess Area

During mining and reclamation,the use of large machinery results in mechanical compaction and severely disturbs on the internal soil pore structure.Soil pore,an important part for soil moisture exchange,determine the soil moisture and air condition and then affect the quality and fertility of reclaimed soils.In this paper,the soil of different degree of compaction in Antaibao opencast coal mine including severe compaction,less severe compaction,moderate compaction,mild compaction and original landform were selected to conduct a scan to obtain the information of soil pore.Soil pore distribution of three-dimensional was reconstructed using the VGstudio software.The three dimensional volume,surface area,mean curvature and connectivity of soil pores were calculated and extracted according to the QuantIm programming software in Linux virtual system platform.Combining with the amount of soil pores and porosity,the effect of mechanical compaction on soil pores was further analyzed.The results indicated that the following conclusions:(1)CT scanning can be used to obtain the information of soil pore distribution characteristics quickly and accurately as an advanced micro-quantitative research method.Three dimensional reconstruction and quantitative characterization of soil pores can be obtained by those scanned images.(2)The soil pore volume,surface area and mean curvature density were negatively correlated with the soil penetration resistance,while the soil pore connectivity density and Euler number were positively correlated with the penetration resistance.(3)The three dimensional parameters of compacted soil pores had good correlation and the correlation coefficients were between 0.786 and 1.000.It can reflect the effects of mechanical compaction on soil pores distribution properties from different aspects.(4)As the compaction degree increased,the porosity and the number of pores at different area and different soil depths decreased.The macropore was the most affected significantly by the mechanical compaction,followed by mesoporosity and microporosity.(5)In the severe compaction area,the number of micropores led to the decrease f the pore surface area density.In the mild compaction area,the number of small pore led to the increase of the pore surface area density.Mechanical compaction led to macropores filled into micropores.The result was that the number of convex pore was small and most pores were horizontal direction.The three-dimensional average curvature of pores was low.In the severe compaction area,more fully isolated pores resulted in poor porosity connectivity;and the mild compaction area had opposite results.This study can provide a theoretical basis for the effective solution of reclamation and compaction problems in opencast coal mine dump in Loess Area.