| The dump is the most serious area of soil erosion in a surface coal mine,which of the loose structure and uneven settlement will induce ground fissure and it has a serious impact on moisture movement,water cycle and vegetation restoration.However,few research works have been done on ground fissures in the dump.Ground fissure is one of the most intuitive geological hazards in coal mining area,and also the most harmful one.It has a large number,extensive distribution,and severe damage,seriously affecting the ecological security of mining area.Taking the south dump of the Shenglidong open-pit coal mine No.2 of Datang international power generation company,in Xilinhot City,Xilingol League,Inner Mongolia as the research object,using field investigation,dye staining experiment,indoor soil physical and chemical properties analysis,artificial rainfall simulation and digital image processing technology,this paper studied the morphology and fractal characteristics of ground fissures,and analysed the physical and chemical properties,mechanical properties and root distribution characteristics with soil layers,revealed the characteristics and influencing factors of preferential flow,clarified the quantitative influence of ground fissure depth and rainfall intensity on soil erosion,and established the calculation model of soil erosion in the dump.The research not only revealed water rapid movement,but also provided scientific basis for the prevention and control of soil erosion in the dump.The main research contents and results were as follows.The fissures were concentrated within the first 5 m from the frontal edge of the dump.Ground fissures were classified into small fissures,medium fissures,and large fissures according to the fissure width W in the dump.The ground fissure width of GF ?,GF?,and GF? was 9.85 cm,2.86 cm,5.77 cm,and there were significant differences among three fissures(P<0.05).That showed that the distribution of ground fissures had self-similarity in the dump.The root in the ground fissures was mainly concentrated in 0-20 cm,which was mainly d<0.1 mm and 0.1 mm<d<0.3 mm.The soil water content and soil water using efficiency were low,and the soil bulk density was high;the saturated hydraulic conductivity of 0-10 cm soil layer was significantly higher than that of other soil layers(P<0.05),and the saturated hydraulic conductivity of 50-60 cm soil layer was significantly lower than that of other soil layers(P<0.05).The destruction rate of soil structure was from 20.52%to 40.56%and the stability of soil aggregates was poor.The stained area was greater than 90%in the 0-5 cm soil layer among the three fissures and water movement was dominated by matrix flow.The stained width decreased from 90 cm to 20 cm with increasing soil depth.The preferential flow was mainly concentrated in both sides of the fissure,which distributed as "T" shape,but there were no significant differences for GF ?,GF? and GF?.Ground fissures,sand content,soil water content,saturated hydraulic conductivity,soil organic matter and plant roots could significantly promote the development of preferential flow of ground fissures.The evolution process of slope erosion in the dump was divided into six stages:soil splash erosion and surface erosion,water filling and collapse of ground fissures,rill erosion,ground fissures through,slope shoulder collapse,stable stage.There was a good power function relationship between runoff and erosion and ground fissure deep.Under rainfall intensity of 90,120,150 mm/h,the slope erosion contribution rate was 92.62%,93.66%,98.98%,respectively.Soil erosion amount of dump was the result of joint effect of ground fissure and rainfall intensity,and its calculation model was E=1.629×10-6H0.318I3.369(R2=0.802,F=18.101,P<0.01,N=7). |
PDF Full Text Request