含瓦斯煤样横向变形与瓦斯流动特性耦合关系试验研究   总被引：2，自引：0，他引：2  

赵洪宝  李华华  杜秋浩  蒋军军 《岩土力学》2013,34(12):3384-3388

以二次成型煤样为研究对象,运用自行研制开发的含瓦斯煤热-流-固耦合三轴伺服渗流试验装置对含瓦斯煤样三轴加载过程中横向变形和与瓦斯流动特性的耦合关系进行了试验研究。结果表明：弹性力学定义的泊松比不能准确表征含瓦斯煤样的横纵应变特性,其关系可用二次函数表征;在预加载荷引起的横压向应变恢复阶段瓦斯流动速度变化呈先急剧降低再缓慢增加特性;在横向应变逐渐向扩张应化转变阶段,煤样内部的瓦斯流动速度呈单调缓慢增加趋势,且存在一个内部结构临界状态点使煤样内瓦斯流动速度最小;含瓦斯煤样处于横向压应变状态起始时的瓦斯流动速度要大于处于横向应变呈扩张状态末端时的瓦斯流动速度。  相似文献   

Fluvial response to an historic lowstand of the Great Salt Lake,Utah     

Krysia Skorko  Paul W. Jewell  Kathleen Nicoll 《地球表面变化过程与地形》2012,37(2):143-156

Understanding fluvial adjustments to base level changes benefits the fields of sequence stratigraphy, geomorphology and petroleum geology. This investigation is a modern case study of the channel dynamics of Lee Creek and the Goggin Drain, two streams that are part of the Jordan River drainage into the endorheic Great Salt Lake of northern Utah, a lacustrine system that has experienced multiple, decadal‐scale base level changes. Since 1965, the lake level has fluctuated in elevation more than 6 m, transitioning from an historic lowstand [< 1279 m above sea level (a.s.l.)] to an historic highstand (>1284 m a.s.l.), and in 2009–2010 approaching an historic lowstand. This study uses detailed aerial images, fieldwork and LiDAR data to link the modern geomorphology and channel hydraulics to specific variations in sediment transport, channel form, and avulsion behavior. Although Lee Creek and the Goggin Drain are situated only a few kilometers apart and share similar shore zone gradients, substrates and vegetation patterns, and have been subjected to the same changes in lake level, their channel forms have evolved very differently. Differences in discharge patterns are likely the most influential factor causing the meandering form of Lee Creek and the braiding channel of the Goggin Drain. Despite the differences in discharge, total sediment eroded from the two streams is comparable and can be attributed to similar stream power/unit stream width in the two streams. Although Lee Creek has not recently been avulsive, three major avulsions of the Goggin Drain have taken place since 1965. Two possible styles of avulsion are interpreted: an allogenic response to changing base level, and an autogenic response dictated by channel morphology and hydraulics. Despite a wealth of available information, avulsions cannot be unequivocally attributed to one style or another. Caution should be used when attempting to link the complex process of avulsion to causal mechanisms. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Paleo-fluvial sedimentation on the outer shelf of the East China Sea during the last glacial maximum   总被引：1，自引：0，他引：1  

王中波  杨守业  张志珣  蓝先洪  顾兆峰  张训华 《中国海洋湖沼学报》2013,31(4):886-894

Evidence from lithology, foraminiferal assemblages, and high-resolution X-ray fluorescence scanning data of core SFK-1 indicates tidally influenced paleo-fluvial sedimentation during the last glacial maximum (LGM) on the outer shelf of the East China Sea. The paleo-fluvial deposits consist of river channel facies and estuarine incised-valley-filling facies. Different reflections on the seismic profile across core SFK-1 suggest that the river channels shifted and overlapped. River channel deposition formed early in the LGM when sea level fell and the estuary extended to the outer shelf. Channel sediments are yellowish-brown in color and rich in foraminifera and shell fragments owing to the strong tidal influence. Following the LGM, the paleo-river mouth retreated and regressive deposition of estuarine and incised-valley-filling facies with an erosion base occurred. The river channel facies and estuarine incised-valley-filling facies have clearly different sedimentary characteristics and provenances. The depositional environment of the paleoriver system on the wide shelf was reconstructed from the foraminiferal assemblages, CaCO₃ content and Ca/Ti ratio. The main results of this study provide further substantial constraints on the recognition of late Quaternary stratigraphy and land-sea interactions on the ECS shelf.  相似文献   

Hydraulic geometry, river sediment and the definition of bedrock channels     

Jens M. Turowski  Niels Hovius  Andrew Wilson  Ming-Jame Horng 《Geomorphology》2008,99(1-4):26-38

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Factors controlling the entrance cross‐sectional areas of four inlets (note)   总被引：1，自引：1，他引：0  

R. A. Heath 《新西兰海洋与淡水研究杂志》2013,47(4):725-735

The frequent occurrence of swell in the entrance to Wellington, Lyttelton, and Akaroa Harbours, coupled with the small littoral drift of sediment on adjacent rocky coastlines, appears to promote development of larger entrances than those associated with tidal control in unconsolidated sediment. In contrast to these three harbours, tidally controlled entrances have either bars or banks that protect them from severe swell and act as bypasses to the littoral drift of sediment.

The entrance to Paterson Inlet lies on a coast with little sediment transport and further protection from sediment influx is provided by islands located at its entrance.  相似文献   

Changes in the epipelic diatom assemblage in nutrient rich streams due to the variations of simultaneous stressors     

《Limnologica》2015

Benthic diatoms are often used for assessing environmental conditions, such as water quality and habitat conditions in stream and river systems. Although laboratory experiments have shown that each diatom species have different levels of tolerance to different stressors, few studies have been conducted in laboratory settings that analyze the responses of the diatom assemblage to the effects of multiple simultaneous variables. The aim of this study was to evaluate some structural responses (such as species composition and diversity) of the diatom assemblage on a short time scale to the effects of the simultaneous increase in four variables that are directly linked to the environmental changes affecting the Pampean streams: turbidity, nutrients (phosphorous and nitrogen), water velocity and temperature. To this end we conducted a five-week laboratory experiment using artificial channels where we simulated two environmental conditions (LOW and HIGH) employing epipelic biofilm from a mesotrophic stream. The results obtained in the experiment show that the structure of the diatom assemblage in the epipelic biofilm is affected by the simultaneous modification of temperature, water velocity, nutrient concentration and turbidity. These modifications in the assemblage included moderate decreases in diversity, small decreases in the proportion of species sensitive to eutrophication and saprobity, moderate increases in the IDP (Pampean Diatom Index) values and moderate changes in the percentages of the stalked growth-forms. The relative abundance of species such as Luticola mutica, Navicula cryptocephala and Navicula lanceolata were negatively affected by both treatments; other species such as Planothidium lanceolatum, Caloneis bacillum, Encyonema minutum, Humidophila contenta, Luticola kotschyi, Nitzschia amphibia, Navicula veneta, Pinnularia subcapitata var. subcapitata were positively affected by the HIGH treatment; and Nitzschia fonticola was positively affected by both treatments. The results suggest that, in the very short term of the bioassay conducted, the diatom assemblage can modify its structure to respond in a sensitive manner to the abrupt changes in multiple physical–chemical variables.  相似文献   

宁波-舟山港口航道3种致病性细菌毒力特征与耐药性     

管峰  高威  陈吉刚  毛芝娟  杨季芳 《海洋学研究》2015,33(4):77-82

本文调查分析了宁波-舟山港口航道副溶血弧菌 Vibrio parahemolyticus、溶藻弧菌Vibrio alginolyticus和嗜水气单胞菌 Aeromonas hydrophila的毒力特征和耐药性特点。用PCR方法检测分离菌株的毒力基因分布模式发现,副溶血弧菌毒力基因型以gyrB⁺,toxR⁺,tlh⁺和 tdh⁺为代表,溶藻弧菌毒力基因型以aspA⁺,tlh⁺,collagenase⁺和toxS⁺为代表,嗜水气单胞菌毒力基因型以aerA⁺,alt⁺,aha1⁺和hlyA⁺为代表;副溶血弧菌、溶藻弧菌和嗜水气单胞菌代表菌株相应基因的检出率分别为57.1%、40.0%和50.0%。用24种常见抗生素对3种细菌的分离代表菌株进行药敏调查,耐药率分别为4.17%、8.33%和29.17%。实验结果表明宁波-舟山港口航道3种致病性细菌具备较丰富的毒力基因种类和耐药性,需要有针对性地制定预防措施。此外,鉴于毒力基因型与致病性之间的相关性,毒力基因可作为标记基因,用于致病性细菌的检测。  相似文献   

Anastamosing channels in the lower Neches River valley,Texas          下载免费PDF全文

Jonathan D. Phillips 《地球表面变化过程与地形》2014,39(14):1888-1899

Active and semi‐active anastomosing Holocene channels upstream of the delta in the lower valley of the meandering Neches River in southeast Texas represent several morphologically distinct and hydrologically independent channel systems. These appear to have a common origin as multi‐thread crevasse channels strongly influenced by antecedent morphology. Levee breaching leads to steeper cross‐valley flows toward floodplain basins associated with Pleistocene meander scars, creating multi‐thread channels that persist due to additional tributary contributions and ground water inputs. Results are consistent with the notion of plural systems where main channels, tributaries, and sub‐channels may have different morphologies and hydrogeomorphic functions. The adjacent Trinity and Sabine Rivers have similar environmental controls, yet the Trinity lacks evidence of extensive anastomosing channels on its floodplain, and those of the Sabine appear to be of different origin. The paper highlights the effects of geographical and historical contingency and hydrological idiosyncrasy. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Breeding,growth, and aestivation of the Canterbury mudfish,Neochanna burrowsius (Salmoniformes: Galaxiidae)   总被引：1，自引：1，他引：0  

G. A. Eldon 《新西兰海洋与淡水研究杂志》2013,47(3):331-346

Neochanna burrowsius (Phillipps) breeds in late winter and spring. Eggs are widely scattered, and adhere to leaves, stems, and suspended roots of aquatic and bankside vegetation in the sluggish or still waters of the adult habitat. Fish were successfully bred in ponds and tanks; hatching time for eggs varied greatly under different conditions of light and temperature. Fry are free swimming until they adopt the nocturnal, cryptic habits of adults when 30–50 mm long. Growth in the first year is rapid, sexual maturity being reached at 1 year old; subsequent growth is slow. Aestivation occurred successfully in shaded vegetable detritus or gravel. Holes were sometimes used, but fish did not make their own burrows for aestivation. When dissolved oxygen was low, captive fish left the water if able to do so without leaving  相似文献   

Comparison of fish populations in riffles of three braided rivers of Canterbury,New Zealand     

G. J. Glova  M. L. Bonnett  C. R. Docherty 《新西兰海洋与淡水研究杂志》2013,47(2):157-165

Populations of small fish were sampled in 12–20 riffles of the lower reaches of 3 braided rivers in Canterbury, New Zealand, during periods of low, stable flows. In the Ashley, which has been least affected by floods in recent years, the standing stock of fish was severalfold higher than in the Hurunui and Rakaia Rivers, which experienced large floods over much of the time, particularly the Rakaia River. Mean abundance + 1 standard deviation (S.D.) of all species combined, amounted to 5.95 + 2.76 fish m ² for 10 species in the Ashley, 0.59 + 0.60 fish m ² for 7 species in the Hurunui, and 0.23 + 0.11 fish m ²for 6 species in the Rakaia. Mean biomass was 24.85 + 9.59, 2.11 + 1.19, and 2.50 ± 3.60 g m ²in the Ashley, Hurunui, and Rakaia Rivers, respectively. The more common species in the Ashley and Rakaia Rivers were torrentfish, longfinned eel, blue‐gilled bully, and upland bully. The same dominant species complex prevailed in the Hurunui River except that the common river galaxias was present instead of the bluegilled bully. The adverse effects of floods on fish, either directly, indirectly, or both, are considered to be a major limiting factor offish populations in braided rivers characterised by highly unstable flows and river beds, and a lack of suitable cover for fish.  相似文献