Effect Of Coal Mining Subsidence On Ecological Environment And Recovery Technique

Shenfu-dongsheng mining area located in the contiguous area of Shanxi, Shaanxi province and Inner Mongolia of southeast Mu Us sandy land. With the increasing coal mining scale in recent years, coal mining subsidence happened with large area in local place and led to loss of water resource, fade and death of vegetation caused by lack of soil moisture, aggravation of wind-sand activity and deterioration of the originally tender ecological environment. In order to research the response relationship between coal mining subsidence and soil-water-vegetation systematically, the technique of field investigation and laboratory analysis and previous reference was used. In this study, subsidence areas subsided in 2004a,2005a and 2006a was selected as references to research the evolution law of local ecological environment and driving mechanism, find out the key restrictive factors aiming at different natural conditions and damaged ecosystems, and to construct suitable ecological recovery technology scientifically. The results were as follows:(1) On the basis of field observation and investigation, the surface collapse form of Shendong mining area after mining was mainly "concave" continuous collapse, "step" continuous collapse and "funnel" discontinuous collapse. The three types appeared meanwhile alternating so that it exacerbated the change of surface environment in the mining process. Based on the investigation and analysis of subsidence crack, the crack formed after mining subsidence activated the dune. One year later, the relation of migration distance of crack and ratio of subsidence fall head and crack width was polynomial function. Two year later, due to the healing of subsidence crack and the formation of new landform, the correction of polynomial function was not obvious. This is means that the formation of subsidence crack lead to the activation of the dune.(2) At the aspect of variation of soil physical properties in coal mining subsidence area:slope of sand dune position, soil moisture of subsidence areas was significantly lower than the corresponding slope position of non-subsidence area, while at lowland position, soil moisture of 2004a subsidence area was significantly lower than the corresponding slope position of non-subsidence area. At the slope position, volume mass of 2005a subsidence area was significantly lower than the corresponding slope position of non-subsidence area, while at lowland position there was no remarkable difference between subsidence areas and non-subsidence area. At the slope position, soil porosity of 2005a subsidence area was significantly higher than the corresponding slope position of non-subsidence area, while no significant'difference was found at lowland position. Hardness of 2005a subsidence area was significantly lower than non-subsidence area at both slope and lowland position, and hardness of 2004a subsidence area showed no remarkable difference compared with non-subsidence area. Infiltration experiment showed that infiltration depth after 55 min at no-crack plot of lowland exceeded non-subsidence area significantly, while infiltration depth at slope position of subsidence areas showed no significant difference compared with non-subsidence area. Multi-factor variance analysis showed that coal mining subsidence caused larger disturbance to relatively exposure side, and this kinds of disturbance recovered at 1-2 a.(3) At the aspect of variation of soil nutrient chemical properties in coal mining subsidence area: pH of no-crack plot groups in lowland of 2004a subsidence area was significantly higher than the lowland of non-subsidence area (P<0.05), and pH of no-crack plot groups in slope of 2004a subsidence area was significantly lower than the slope of non-subsidence area (P<0.05). Total N of no-crack plot groups in 2004a subsidence area was significantly lower than the slope of non-subsidence area (P<0.05). Alkaline hydrolytic N of crack plot groups at slope of non-subsidence area significantly increased compared with slope of non-subsidence area (P<0.05). Total P of no-crack plot group and crack plot group in slope of 2004a subsidence area was significantly lower than slope of non-subsidence area (P<0.05). Total K of no-crack plot groups in slope of 2005a subsidence area exceeded slope of non-subsidence area significantly (P<0.05). Available K of no-crack plot group and crack plot group in slope of 2004a subsidence area was significantly lower than slope of non-subsidence area (P<0.05). Available P and Organic matter showed no significant difference at each slope position (P>0.05).(4) At the aspect of variation of vegetation in coal mining subsidence area:species number and vegetation coverage of 3 survey areas in 6 mines showed same tendency that is subsidence area had more kinds of plant species and larger vegetation coverage compared with non-subsidence area.2005a subsidence area had more kinds of plant species and larger vegetation coverage compared with 2004a subsidence area. Correlation analysis showed that, correlation coefficient of subsidence age limits, subsidence and non-subsidence, and plant species exceeded 0.85, and correlation coefficient of vegetation coverage exceeded 0.9, which showed obvious correlation and showed that affect vegetation in some degree. Subsidence caused no significant effect to vegetation coverage and the growth of constructive species. Species number and vegetation coverage showed correlation to subsidence and subsidence age limits. Rich degree of plant species and vegetation coverage exhibits some correlation to subsidence.(5) Base on qualitative and quantitative analysis, method that mixed with experiment and investigation was used to establish construction technique of ecological function cycle before mining, diagnosis essential feature, reason, process, type and degree and so on of regional ecological degradation, and to ensure the realize target of ecological restoration according to the natural condition of coal mining subsidence area. Base on current work, proper ecological rehabilitation technologies were integrated, ecological rehabilitation zone was established, ecological rehabilitation path was forecasted and repair effect was evaluated to offer technical and practical basis for constructing favorable ecological cyclic utilization system and increasing economic benefit.