桥墩墩型对平衡冰塞水位影响的试验研究          下载免费PDF全文

王军  黄宁静  吴一帆  程铁杰 《水科学进展》2018,29(4):568-573

冰塞的出现使上游水位壅高,极易诱发凌洪灾害。桥墩墩型是影响桥墩附近冰塞壅水的重要因素之一。通过模型试验,对不同墩型影响下的平衡冰塞水位增值过程进行研究,并与无桥墩条件和明流情况进行了对比。试验结果表明:在试验冰水流量比条件下,当Fr≤0.145时,无桥墩条件下平衡冰塞水位增值小于有桥墩;当Fr>0.145时,无桥墩条件下平衡冰塞水位增值大于有桥墩;桥墩墩型引起的平衡冰塞水位增值由大到小排序为长方形桥墩、尖端形桥墩、圆端形桥墩和圆柱形桥墩。易发生冰塞的河段,建造桥梁时应当尽量选用圆柱形、圆端形桥墩。  相似文献   

Study on Environmental and Hydrological Effects of Thermokarst Lakes in Permafrost Regions of the Qinghai-Tibet Plateau     

Fujun Niu  Wei Wang  Zhanju Lin  Jing Luo 《地球科学进展》2018,33(4):335-342

Thermokarst lake is the most visible morphologic landscape developing during the process of permafrost degradation, and it is still an international hot topic in permafrost research. The climate warming, and the consequent degradation of the permafrost on the Qinghai-Tibet Plateau aggravate thermokarst lake development. The permafrost is normally considered as an aquiclude, and the permafrost degradation, especially when the permafrost is completely thawed by a thermokarst lake, might influence regional ground water. Therefore, a research program focusing on environmental and hydrological effects of thermokarst lakes in permafrost regions of the Qinghai-Tibet Plateau was started and supported by the National Natural Science Foundation of China. The work proposed by the application includes: To analysis the spatial and temporal distribution rule of thermokarst lakes in the Qinghai-Tibet Engineering Corridor (QTEC) under the climate change and engineering activities, and to evaluate the ecological environment effects through remote sensing and field investigation; to reveal the main factors influencing a typical thermokarst lake and its hydrothermal condition, and to elucidate the conversion relationship between the thermokarst lake and the groundwater with hydrological and isotope tracer tests; to make an analysis of the influences of different lake stage and size on regional permafrost, hydrological conditions and ecological environment through numerical simulation and statistical modelling, considering the relationships between the thermokarst lake and the ground water level. The research results will help to accurately assess regional permafrost ecological environment evolution and trend prediction, and to reasonably understand the impact factors of the permafrost hydrological evolution and its response mechanism to the ecological environment in the river source regions of the Qinghai-Tibet Plateau. In this paper, the research status analysis, the main research contents, research objectives and prospects were introduced so as to provide some references for related researchers and engineers.  相似文献   

辽北地区新元古代原殷屯组岩石地层单位的重新划分及其地质意义     

卢崇海  田德欣  李彪  邵九龙  刘振伟  赵娇  卢思桥 《世界地质》2018,37(4):1085-1091

本次研究把20世纪八十年代初期完成的辽宁1∶5万大甸子、下肥地和上年马洲幅区调报告中所建立的震旦系殷屯组3个岩性段,即底部砾岩段、中部砂岩段和上部板岩、页岩段,分别厘定为新元古界北方系(南华系)殷屯组、陈千户组和汎河组。并确认出殷屯组为辽宁北方系(南华系)第一次陆相冰碛作用的产物;陈千户组为陆相间冰期沉积的产物;汎河组为辽宁第二次陆相冰湖相堆积的产物。上述组级岩石地层单位的厘定,首次在辽宁北部地区划分出2次冰水堆积物。  相似文献   

The role of megatides and relative sea level in controlling the deglaciation of the British–Irish and Fennoscandian ice sheets          下载免费PDF全文

J. D. Scourse  S. L. Ward  A. Wainwright  S. L. Bradley  K. Uehara 《第四纪科学杂志》2018,33(2):139-149

Key external forcing factors have been proposed to explain the collapse of ice sheets, including atmospheric and ocean temperatures, subglacial topography, relative sea level and tidal amplitudes. For past ice sheets it has not hitherto been possible to separate relative sea level and tidal amplitudes from the other controls to analyse their influence on deglaciation style and rate. Here we isolate the relative sea level and tidal amplitude controls on key ice stream sectors of the last British–Irish and Fennoscandian ice sheets using published glacial isostatic adjustment models, combined with a new and previously published palaeotidal models for the NE Atlantic since the Last Glacial Maximum (22 ka BP). Relative sea level and tidal amplitude data are combined into a sea surface elevation index for each ice stream sector demonstrating that these controls were potentially important drivers of deglaciation in the western British Irish Ice Sheet ice stream sectors. In contrast, the Norwegian Channel Ice Stream was characterized by falling relative sea level and small tidal amplitudes during most of the deglaciation. As these simulations provide a basis for observational field testing we propose a means of identifying the significance of sea level and tidal amplitudes in ice sheet collapse.  相似文献   

静水条件下冰冻泥沙水下休止角的试验研究     

王鑫  邓云  冯镜洁  秦鑫  脱友才 《冰川冻土》2018,40(5):979-984

为研究冰冻泥沙在静水中融化后休止角的变化规律以及不同环境中泥沙休止角的差异,采用粒径为0～1 mm、1～2 mm、2～4 mm的泥沙试样,进行了风干泥沙在空气中的休止角、无冰泥沙以及冰冻泥沙水下休止角试验。试验结果表明：对于同一粒径范围的泥沙,风干沙在空气中的休止角最大,冰冻泥沙水下休止角次之,无冰泥沙水下休止角最小,三种试验情景中休止角均随泥沙粒径的增大而增大;泥沙水下休止角与风干沙在空气中休止角的差异,主要与水对泥沙的润滑作用以及泥沙在不同介质中的有效容重系数有关;泥沙在水下受到冰的影响表现为局部泥沙颗粒滑动,这更有利于斜坡上泥沙的堆积,相对于无冰泥沙而言,冰的存在使泥沙水下休止角增大。  相似文献   

冰层空气反循环连续取芯钻具：结构设计与冰芯卡断数值模拟     

陈宝义  范大友  王如生  达拉拉伊  陈艳吉 《探矿工程》2018,45(9):46-50

冰心包含大量的古气候资料和古生物学信息,这些信息对于从远古到现代的气候变化和生物进化都很重要。如何高效快速地获取无污染的冰心是极地科学家的一个重要课题。冰层空气反循环钻具采用双壁钻杆形成反循环通道,内管提供了从钻头底部到表面的冰屑和冰心的连续通道。钻具通过卡断机构卡断冰心,通过反循环通道不断运移冰心,从而实现连续钻具连续取心。本文采用ABAQUS软件对冰心卡断过程进行分析,运用XFEM断裂准则以及Explicit显式方法求解,选出适宜的卡断器尺寸和中心通道尺寸,从而得到更好的反循环钻进效果。  相似文献   

极地深冰钻用减速传动装置设计          下载免费PDF全文

李鲁佳  郑治川 《探矿工程》2018,45(2):36-40

在前期研发的极地深冰钻用减速传动装置中,行星齿轮减速传动装置易发生疲劳破坏,因此减速传动装置寿命相对较低。针对上述问题,对铠装电缆电动机械钻具的减速传动装置进行改进设计,确定装置的结构和尺寸、分析该装置的啮合受力情况并进行强度估算。利用Inventor软件建立该减速传动装置三维实体模型。结合ANSYS Workbench软件对装置的结构进行静力学分析。研究结果表明,该活齿传动减速传动装置满足设计要求,为优化极地深冰钻用减速传动装置提供了依据。  相似文献   

超声波冰层钻进方法的可行性研究          下载免费PDF全文

王晨  赵大军  王美艳  张书磊  王雨  李政阳 《探矿工程》2018,45(10):123-126

人类对极地资源的开采和科学研究需要高效、环保的冰层钻探技术,热熔钻进是常用方法之一。为解决热熔钻进技术能量利用率低的问题,本文提出了一种以超声波频率振动进行冰层钻进的方法,分析了超声波振动钻进冰层的机理,通过超声波振动冰层钻进效率的计算及室内试验,得出了超声波振动冰层钻进速度大、热效率高的结论,可用于极地冰盖、冰架等冰层的钻进。  相似文献   

南极冰盖内部等时层研究进展综述          下载免费PDF全文

唐学远  孙波  崔祥斌 《极地研究》2015,27(1):104-114

南极冰盖内部等时层记录了不同时期冰盖表面的特征及其演变,蕴含了丰富的冰下环境信息。目前,已成为研究大空间尺度与长时间尺度上南极冰盖演化及其底部环境的重要媒介。地球物理观测和数值模拟技术的综合使用,实现了南极冰盖内部等时层在大陆尺度上的可视化。通过这些内部等时层,冰川学研究将南极冰盖内部的古冰流与千年至百万年时间尺度的地貌及冰下环境的变化细节联系起来,得到了一系列数量化的结果。针对南极冰盖,综述产生内部等时层的冰盖动力学物理机理及其在冰川学上的应用,评估在五个方面的运用:(1)深冰芯断代与选址;(2)冰盖动力学过程;(3)冰盖物质平衡;(4)冰盖稳定性;(5)冰下环境。另外,基于对内部等时层的已有认识,对未来在内部等时层研究中可能需要强化的领域进行了归纳:(1)发展更精细描述并测试内部等时层结构时空变化的数值模拟技术框架面临的挑战;(2)如何从内部等时层蕴含的信息推断鉴别以目前南极冰盖作为初始条件的冰盖质量变化;(3)为获得更高分辨率的内部等时层结构图像,得到关于冰盖内部冰体形变与演化的更多数量化信息,如何强化冰盖冰下环境的重复观测。  相似文献   

Sediment‐rich meltwater plumes and ice‐proximal fans at the margins of modern and ancient tidewater glaciers: Observations and modelling          下载免费PDF全文

Julian A. Dowdeswell  Kelly A. Hogan  Neil S. Arnold  Ruth I. Mugford  Martin Wells  J. Philip P. Hirst  Carole Decalf 《Sedimentology》2015,62(6):1665-1692

Turbid meltwater plumes and ice‐proximal fans occur where subglacial streams reach the grounded marine margins of modern and ancient tidewater glaciers. However, the spacing and temporal stability of these subglacial channels is poorly understood. This has significant implications for understanding the geometry and distribution of Quaternary and ancient ice‐proximal fans that can form important aquifers and hydrocarbon reservoirs. Remote‐sensing and numerical‐modelling techniques are applied to the 200 km long marine margin of a Svalbard ice cap, Austfonna, to quantify turbid meltwater‐plume distribution and predict its temporal stability. Results are combined with observations from geophysical data close to the modern ice front to refine existing depositional models for ice‐proximal fans. Plumes are spaced ca 3 km apart and their distribution along the ice front is stable over decades. Numerical modelling also predicts the drainage pattern and meltwater discharge beneath the ice cap; modelled water‐routing patterns are in reasonable agreement with satellite‐mapped plume locations. However, glacial retreat of several kilometres over the past 40 years has limited build‐up of significant ice‐proximal fans. A single fan and moraine ridge is noted from marine‐geophysical surveys. Closer to the ice front there are smaller recessional moraines and polygonal sediment lobes but no identifiable fans. Schematic models of ice‐proximal deposits represent varying glacier‐terminus stability: (i) stable terminus where meltwater sedimentation produces an ice‐proximal fan; (ii) quasi‐stable terminus, where glacier readvance pushes or thrusts up ice‐proximal deposits into a morainal bank; and (iii) retreating terminus, with short still‐stands, allowing only small sediment lobes to build up at melt‐stream portals. These modern investigations are complemented with outcrop and subsurface observations and numerical modelling of an ancient, Ordovician glacial system. Thick turbidite successions and large fans in the Late Ordovician suggest either high‐magnitude events or sustained high discharge, consistent with a relatively mild palaeo‐glacial setting for the former North African ice sheet.  相似文献