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11.
针对近浅埋综采面过山丘地形发生强矿压显现的问题,采用现场监测、理论分析与数值模拟相结合的方法,建立山丘静载应力传递模型和不同岩层赋存特征的沙土型与土石型山丘工作面关键块体结构力学模型,分析山丘地形工作面矿压发生机理。研究表明:山丘静载向工作面传递的垂直应力呈钟形分布,山丘高静载应力易激发弱铰接结构失稳;山丘坡体中关键层的有无导致了土石型和沙土型山丘工作面矿压发生机理的差异性;坡体断裂块的倾斜回转运动是沙土型山丘工作面发生强矿压的主导因素,断裂块不同的倾斜回转方向导致工作面在上坡段矿压显现缓和而下坡段显现剧烈;土石型山丘工作面的矿压显现主要受坡体中关键块体结构稳定状态的控制,工作面在上坡初和坡顶段动载矿压强烈而下坡段后期较缓和。数值计算结果与现场监测和理论分析相符。 相似文献
12.
Xiao WANG Fanghua HAO Xuan ZHANG Wen SUN Hongguang CHENG 《Frontiers of Environmental Science & Engineering in China》2008,2(3):318-325
Environmental risk of high sulfur gas field exploitation has become one of the hot spots of environmental management studies.
Severe gas H2S blowout accidents in recent years have shown that poor understanding and estimates of the poisonous gas movement could lead
to dangerous evacuation delays. It is important to evaluate the real concentration of H2S, especially in complex terrain. Traditional experiential models are not valid in the case of rough terrain, especially in
low-lying areas where the gas accumulates. This study, using high sulfur content gas field of Sichuan “Pu Guang gas field”
as study object and adopting objective diagnosis of wind field of land following coordinate three dimensions, applied Lagrangian
Puff Model and breaking up technique of puffs to simulate the H2S diffusion condition of blowout accidents produced in the high sulfur content gas field of complex terrain area. The results
showed that the H2S distribution did not occur mainly in low wind direction, and due to the obstruction of the mountain’s body, it accumulated
in front of mountain on produced turn over, flowed around submitted jumping type distribution. The mountain waist near the
hilltop and low hollow river valley site rapture points simulating contrast showed that the higher the rapture point, the
better the diffusing condition of pollutant, the distribution of risk sensitive point decided piping rupture environmental
risk size combining the H2S diffusion result and residential area dispersing in the study area, synthetic judge located in the high rapture point environmental
risk was smaller than the low hollow point, thus it was suggested to carryout laying of lining build of equal high line of
higher terrain. According to simulation results, the environmental risk management measures aimed at putting down adverse
effects were worked out. 相似文献
13.
为了解地貌在坡面尺度上对α生物多样性的影响,采用主观采样法在陕北吴起县合家沟流域不同地貌部位进行了样地调查.利用SPSS16.0统计软件先后对各地貌部位物种组成及各物种的重要值、地形因子要素间、地形因子和群落α多样性之间分别做了聚类分析、相关分析和多元回归分析.结果表明:(1)地貌部位相似的群落聚类在一起,说明地形因子是影响物种组成、群落结构、生态系统等的重要因素.(2)海拔和坡位,坡向和坡度,地形指数和海拔、坡位、坡形之间的Pearson 相关系数均大于0.8,双尾显著性检验概率小于0.05.(3)影响α生物多样性指标香农-维纳指数的地形因子按重要性从大到小依次是:坡位、坡向、海拔、坡形、坡度、地形指数,进一步分析得出在黄土高原丘陵沟壑区,沟沿线、光照、土壤水分和养分在影响α生物多样性指标上依次递减.(4)通过多元线形回归检验,得出坡位、坡向、坡形、海拔这四个地形因子与群落α生物多样性关系密切,建立的回归模型显著性检验可信度大,与样本数据的拟合度高.各地形因子数据归一处理后的回归方程为:香农-维纳指数=2.417-0.581×坡形-1.333×坡位+1.449×海拔+0.631×坡向.地形地貌特征在黄土丘陵区表现明显,研究它对生物多样性的影响可为该区植被恢复提供参考,但由于调查样地尺度较小,在应用推广上尚待进一步研究. 相似文献
14.
15.
为了研究采场在覆岩运动过程中关键层的缺失与否对综采工作面采场矿压的影响效果,采用相似模拟试验和数值模拟,对大柳塔煤矿活鸡兔井1-2煤21304综采工作面在回采期间出现的2次压架事故进行分析。研究结果表明:上覆岩层的关键层缺失与否对下部煤层的开采影响至关重要,尤其是对上部已采单一关键层的煤层回采影响较大,当上煤层的关键层未缺失时回采后形成稳定的砌体梁结构,其下煤层回采也易形成稳定的砌体梁结构,反之亦然;在冲沟发育较深的地形,关键层的形成也会受到冲沟影响,造成部分关键层缺失,当关键层缺失时工作面向坡开采,随着工作面所承受的荷载逐渐增大,出现动载矿压的几率也随之增加,背坡开采则与之相反。 相似文献
16.
Yuichi Yamaura David Lindenmayer Yusuke Yamada Hao Gong Toshiya Matsuura Yasushi Mitsuda Takashi Masaki 《Conservation biology》2020,34(1):194-206
Stand structure develops with stand age. Old-growth forests with well-developed stand structure support many species. However, development rates of stand structure likely vary with climate and topography. We modeled structural development of 4 key stand variables and a composite old-growth index as functions of climatic and topographic covariates. We used a hierarchical Bayesian method for analysis of extensive snap-shot National Forest Inventory (NFI) data in Japan (n = 9244) to account for differences in stand age. Development rates of structural variables and the old-growth index exhibited curvilinear responses to environmental covariates. Flat sites were characterized by high rates of structural development. Approximately 150 years were generally required to attain high values (approximately 0.8) of the old-growth index. However, the predicted age to achieve specific values varied depending on environmental conditions. Spatial predictions highlighted regional variation in potential structural development rates. For example, sometimes there were differences of >100 years among sites, even in the same catchment, in attainment of a medium index value (0.5) after timber harvesting. The NFI data suggested that natural forests, especially old natural forests (>150 years), remain generally on unproductive ridges, steep slopes, or areas with low temperature and deep snow, where many structural variables show slow development rates. We suggest that maintenance and restoration of old natural forests on flat sites should be prioritized for conservation due to the likely rapid development of stand structure, although remaining natural forests on low-productivity sites are still important and should be protected. 相似文献
17.
I. Mammarella F. Tampieri M. Tagliazucca M. Nardino 《Environmental Fluid Mechanics》2005,5(3):227-246
Turbulence measurements were performed in Antarctica, on the Nansen Ice Sheet, dominated by westerly katabatic winds. The measurements were taken at two sites aligned with the katabatic wind fall-line. The measuring stations were located in the middle of a wide, flat iced area at a distance of 14 km from the base of a sloping surface and at the top of a steep ridge (Inexpressible Island). The aim was to investigate the perturbation of turbulence close to the ground generated by the interaction of the flow with the ridge. We present an analysis comparing the data measured at the upstream unperturbed station with those at the top of the obstacle. Moments and spectra of velocity components have been calculated for almost steady periods. The topography and roughness change produce a combined effect on the flow acceleration (of the opposite sign) and on the turbulent stresses (of the same sign). Spectra of velocity components measured at the top of the ridge and scaled by unperturbed quantities evidence an increment of energy in the high frequency subrange with respect to the up-stream flow. Moreover, the horizontal velocity components display a shift in turbulence maximum towards higher frequencies. The vertical velocity spectrum exhibits an energy increment at low frequencies with respect to the upstream spectrum. 相似文献
18.
This study improved the application of the Holdridge life-zone model to simulate the distribution of desert vegetation in China which gives statistics to support eco-recovery and ecosystem reconstruction in desert area. This study classified the desert vegetation into four types: (1) LAD: little arbor desert; (2) SD: shrub desert: (3) HLHSD: half-shrub, little half-shrub desert; (4) LHSCD: little halfshrub cushion desert. Based on the classification of Xinjiang desert vegetation, the classical Holdridge life-zone model was used to simulate Xinjiang desert vegetation's distribution and compare the Kappa coefficient result of the model with table of accuracy represented by Kappa values. The Kappa value of the model was only 0.19, it means the simulation result was poor. To improve the life-zone model application to Xinjiang desert vegetation type, a set of plot standards for terrain factors was developed by using the plot standard as the reclassification criterion to climate sub-regime. Then the desert vegetation in Xinjiang was simulated. The average Kappa value of the second simulation to the respective climate regime was 0.45. The Kappa value of final modeling result was 0.64, which is the better value. The modification of the model made it in more application region. In the end, the model' s ecological relevance to the Xinjiang desert vegetation types was studied. 相似文献
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“尤德地体”位于闽中裂谷带南端 ,与紫金山金矿处于同一成矿带。在“尤德地体”中 ,目前已发现元古界麻源群变质岩和侏罗系长林组、南园组 ,火山岩中均存在韧性剪切带型矿床和热液交代充填矿床。区域构造、地层含矿性、物化探重砂异常等表明其找矿前景很好。找矿工作重点应紧扣层控矿床 ,大断裂带 ,斑岩型金矿和红土型金矿 相似文献