In recent years,the ecological quality of ditches became worse and worse with the degradation of its ecological functioning.It was necessary to apply a multi-disciplinary and multi-scale approach to study ditches base...In recent years,the ecological quality of ditches became worse and worse with the degradation of its ecological functioning.It was necessary to apply a multi-disciplinary and multi-scale approach to study ditches based on landscape ecology theory.Spatial and network features of agricultural ditches in Lake Dianchi Basin were analyzed by geographic information system technology.The results indicated that the ditches at high level were made by concrete or block stones,the coverage of vegetation of buffer zones and width ratio between ditch sections and vegetation zones were very low;The network of agricultural ditches in Lake Dianchi basin had similar characteristics,the connectivity and circuitry were low,and the fractal dimension index of ditch network were larger in southeastern and southern banks.展开更多
Underground pressure is abnormal during mining of shallow coal seams under gullies. We studied gully slope movements, subject to underground mining, with physical simulation and theoretical analysis. The rules disclos...Underground pressure is abnormal during mining of shallow coal seams under gullies. We studied gully slope movements, subject to underground mining, with physical simulation and theoretical analysis. The rules disclose that the slope rock slides horizontally in response to mining in the direction of gullies and rotates reversely with the appearance of a polygon block in mining away from gullies. We focused our attention on the case of mining away from a gully. We built a mechanical model in terms of a polygon block hinged structure and investigated the variation of horizontal thrust and shear force at the hinged point in relation to the rotation angle under different fragmentations. The Sliding-Rotation instability conditions of the polygon block hinged structure are presented based on the analyses of sliding instability and rotation instability. These results can serve as a theoretical guide for roof control during mining away from gullies in a coalfield defined by gullies.展开更多
By using the simulated ditch experiment,the differences of nitrogen and phosphorus absorption capacities of 9 aquatic plants were studied,and the better varieties of nitrogen and phosphorus absorption capacity were se...By using the simulated ditch experiment,the differences of nitrogen and phosphorus absorption capacities of 9 aquatic plants were studied,and the better varieties of nitrogen and phosphorus absorption capacity were selected to construct the ecological ditch and oxidation pond to study the nitrogen and phosphorus absorption effect.The results showed that the nitrogen and phosphorus residues in the simulated ditch water were signi ficantly reduced after planting aquatic plants.The biomass of Canna glauca,Myriophyllum elatinoides,Sorbaria sorbifolia,Pontederia cordata and Zizania was high,and the uptakes of nitrogen and phosphorus were high.Among them,the effect of planting Canna glauca and Myriophyllum elatinoides was the best.The concentration of nitrogen and phosphorus in farmland drainage decreased signi ficantly after being absorbed by aquatic plants in ecological ditches;the concentration of total nitrogen,soluble nitrogen and total phosphorus in main ditches decreased by 39.6%,40.1% and 36.9% respectively on average;the concentration of total nitrogen,soluble nitrogen and total phosphorus in branch ditches decreased by 6.6%,10.3% and 13.6% on average.The concentration of total nitrogen and total phosphorus in the oxidation pond could be further reduced by 17.7%and 13.3%.Ecological ditches can effectively intercept nitrogen and phosphorus in water,and have good ecological benefits of purifying water to obtain improved water quality.展开更多
基金Supported by National Key Sciences and Technology Program for Water Solutions (2008ZX07102-004) ~~
文摘In recent years,the ecological quality of ditches became worse and worse with the degradation of its ecological functioning.It was necessary to apply a multi-disciplinary and multi-scale approach to study ditches based on landscape ecology theory.Spatial and network features of agricultural ditches in Lake Dianchi Basin were analyzed by geographic information system technology.The results indicated that the ditches at high level were made by concrete or block stones,the coverage of vegetation of buffer zones and width ratio between ditch sections and vegetation zones were very low;The network of agricultural ditches in Lake Dianchi basin had similar characteristics,the connectivity and circuitry were low,and the fractal dimension index of ditch network were larger in southeastern and southern banks.
基金Financial support for this work, provided by the Research Fund of the Fundamental Research Funds for the Central Universities of China University of Mining & Technology (No. 2010ZDP02B02)the State Key Laboratory of Coal Resources and Mine Safety (No. SKLCRSM08X2)+1 种基金the Jiangsu "333" High Qualified Talents, the National Natural Science Foundation of China (Nos. 50904063 and 51004101)the Scientific Research Foundation of China University of Mining & Technology (Nos. 2008A003 and 2009A001)
文摘Underground pressure is abnormal during mining of shallow coal seams under gullies. We studied gully slope movements, subject to underground mining, with physical simulation and theoretical analysis. The rules disclose that the slope rock slides horizontally in response to mining in the direction of gullies and rotates reversely with the appearance of a polygon block in mining away from gullies. We focused our attention on the case of mining away from a gully. We built a mechanical model in terms of a polygon block hinged structure and investigated the variation of horizontal thrust and shear force at the hinged point in relation to the rotation angle under different fragmentations. The Sliding-Rotation instability conditions of the polygon block hinged structure are presented based on the analyses of sliding instability and rotation instability. These results can serve as a theoretical guide for roof control during mining away from gullies in a coalfield defined by gullies.
文摘By using the simulated ditch experiment,the differences of nitrogen and phosphorus absorption capacities of 9 aquatic plants were studied,and the better varieties of nitrogen and phosphorus absorption capacity were selected to construct the ecological ditch and oxidation pond to study the nitrogen and phosphorus absorption effect.The results showed that the nitrogen and phosphorus residues in the simulated ditch water were signi ficantly reduced after planting aquatic plants.The biomass of Canna glauca,Myriophyllum elatinoides,Sorbaria sorbifolia,Pontederia cordata and Zizania was high,and the uptakes of nitrogen and phosphorus were high.Among them,the effect of planting Canna glauca and Myriophyllum elatinoides was the best.The concentration of nitrogen and phosphorus in farmland drainage decreased signi ficantly after being absorbed by aquatic plants in ecological ditches;the concentration of total nitrogen,soluble nitrogen and total phosphorus in main ditches decreased by 39.6%,40.1% and 36.9% respectively on average;the concentration of total nitrogen,soluble nitrogen and total phosphorus in branch ditches decreased by 6.6%,10.3% and 13.6% on average.The concentration of total nitrogen and total phosphorus in the oxidation pond could be further reduced by 17.7%and 13.3%.Ecological ditches can effectively intercept nitrogen and phosphorus in water,and have good ecological benefits of purifying water to obtain improved water quality.
