共查询到18条相似文献，搜索用时 187 毫秒
1.
2.
采用平面二维水动力数值模拟方法,对伊洛河交汇区河段的错峰洪水特性进行了系统分析,讨论了洪水水位、流态及两支流的相互影响,结果表明:数值模拟成果与实测数据有很好的一致性。研究发现:交汇区流场呈现马鞍形水面形态,并随流量增大向下游推进;错峰洪水过程中强势支流产生的漫滩水流对弱势支流形成壅堵,交汇区水动力要素与流态均与强、弱支流流量比有明显的关联性,交汇点下游的螺旋流结构与转向受当时强势支流控制;错峰洪水使交汇区水位随时间变化呈现三段式二次曲线特征,在两洪峰期间交汇区保持高水位的时间比单峰或同峰长5~7倍;错峰洪水使交汇区洪水位与流量形成特殊的Y型曲线关系,在两个洪峰点附近,水位与汇流比的对应关系出现前、后两个拐点。 相似文献
3.
4.
针对黄河上游干、支流交汇区形成的沙坝淤堵事件,利用野外观测资料,分析了支流高含沙洪水特性及交汇区沙坝淤堵特点,探讨了汇流比(支流流量与干流流量之比)、支流洪水水量、支流洪水沙量等因素对沙坝淤堵形成的影响;根据动量原理建立了交汇区形成沙坝淤堵的判别关系,结合黄河上游干、支流洪水输移特性,得出了基于汇流比与支流洪水水量关系及支流洪水沙量与支流洪水水量关系的沙坝淤堵判别条件。由此,可根据汇流比、支流洪水水量及沙量判断交汇区能否形成沙坝淤堵,可为暴雨洪水期黄河上游交汇区形成沙坝淤堵灾害的预报及防治提供参考。 相似文献
5.
针对天然河流交汇区域复杂的地形条件及水流运动特性,采用水气两相流三维数值模型,对长江与嘉陵江交汇区水流运动进行深入研究,分析了交汇区域分离区、剪切层、流速场及螺旋度的变化特性。研究结果表明:长江与嘉陵江交汇的水流分离区形状受地形影响明显,随着水位的增加向右岸移动,剪切层整体呈一个扭曲的曲面;干支流原有的环流在交汇之后重新汇合,左岸未出现明显的环流,右岸逆时针的环流有减弱趋势,交汇区域纵向流速呈现高速与低速带分布特征。此外,长江和嘉陵江在交汇口下游螺旋度呈现左侧为负、右侧为正的对称分布,水流结构表现出逐渐形成双螺旋流的趋势,其中左侧的螺旋流逆时针运动,右侧的螺旋流顺时针运动。 相似文献
6.
岩溶区嵌岩桩承载特性影响因素试验研究 总被引：2，自引：0，他引：2
基于室内模型试验,对岩溶区嵌岩桩承载能力的影响因素进行了研究。试验表明,随顶板厚度与溶洞位置偏移距离的增大,极限承载力逐渐增大,随溶洞直径、赤道半径与极半径的增大,极限承载力逐渐减小;破坏核体在竖直方向上基本未超过3d（d为桩体直径）范围,在水平方向上基本未超过4d范围。结合模型试验结果,影响因素的敏感性分析表明,敏感度大小的顺序为：溶洞直径>顶板厚度、赤道半径>极半径>溶洞位置。嵌岩桩的承载能力还与溶洞形状有关,厚径比为溶洞顶板厚度、赤道半径以及桩体底面积的综合影响因素,建议引进形状系数? 与底面积尺寸效应系数?,提出岩溶区嵌岩桩概念设计的注意事项,并通过工程实例进行了验证,现场静载试验与模型试验结果基本一致,楼房竣工后未发生岩溶危害。 相似文献
7.
为研究明渠水流自掺气发展区内水气结构特征,采用针式掺气流速仪对自掺气发展区内气泡尺寸与数量进行了试验研究,比较了气泡尺寸与数量随自掺气发展的变化规律,结果显示,同一水流断面上,随着掺气浓度的减小,气泡弦长尺寸分布范围与弦长平均值逐渐减小,掺气区内小尺寸气泡在数量上占有较大的比例,而大尺寸气泡则在含气量上占有较大的比例,分析认为从水面附近高掺气浓度区至自掺气区域底缘低掺气浓度区,明渠自掺气水流水气结构发展过程为“水面变形为主—水面变形与个体空气泡共存—个体空气泡”,为进一步研究明渠自掺气形成机理提供了一定的参考。 相似文献
8.
与顺直明渠水流相比,明渠交汇水流由于存在分离区和自由剪切面,其紊动特性引起的阻力较为复杂,交汇水流除床面阻力外还受到较强的阻力。基于数值模拟与实验比较分析表明,分离流与自由剪切流所产生的阻力(紊动粘性阻力)对于交汇水流数值模拟具有重要影响。同时,由于平面二维模型对二次流影响的忽略,断面环流较强时数值模拟会产生较大的阻力(环流阻力),而断面环流较弱时,交汇水流的三维特性相对较弱,采用平面二维模型和k-ε紊流模型能达到较好的模拟效果。因此,紊动及环流阻力的计算对交汇水流数值模拟的精度至关重要。 相似文献
9.
为深入探讨硬煤的煤与瓦斯突出机制,对深部硬煤掘进工作面煤与瓦斯突出的相关理论和模型试验进行研究。根据断裂力学、岩石力学及煤与瓦斯突出有关理论,提出深部开采过程中硬煤掘进工作面薄板理论假设,并将该理论应用于深部硬煤掘进工作面煤与瓦斯突出模拟试验研究。对硬煤掘进工作面薄板理论分析,认为工作面尺寸、煤的弹性模量、围岩侧压系数、瓦斯压力等因素对硬煤掘进工作面突出具有较大影响。试验结果表明,在围岩应力、煤的坚固性系数较大的情况下,硬煤突出临界条件主要受围岩应力、煤的弹性模量、围岩侧压系数及工作面尺寸等因素影响,而受瓦斯压力影响相对较小;在围岩应力、试样的坚固性系数较大且煤的弹性模量和侧压系数稳定不变的情况下,发生突出的临界轴向应力随模拟工作面尺寸增大而近似呈线性减小。试验结论基本符合本硬煤突出薄板模型理论公式,在一定程度上验证了硬煤掘进工作面煤薄板模型理论及硬煤掘进工作面突出机制假设。 相似文献
10.
11.
12.
A field study of turbulence and sediment dynamics over subaqueous dunes with flow separation 总被引：1，自引：0，他引：1
Ray Kostaschuk 《Sedimentology》2000,47(3):519-531
This study examines flow, turbulence and sand suspension over large dunes in Canoe Pass, a distributary channel of the Fraser River delta, Canada. Dune morphology is characterized by a symmetrical shape and steep leeside slopes over 30°. Velocity was measured with an electromagnetic current meter and suspended sand concentration with four optical backscatter (OBS) probes. The general patterns of time-averaged velocity and sand suspension are consistent with previous studies, including an increase in mean velocity and decrease in turbulence intensity and sand concentration with height above the bed, reversed flow with high turbulence intensity and high sand concentrations in the leeside flow separation zone and an increase in near-bed velocity and sand concentration along the stoss side of the dune. Frequency spectra of near-bed velocity and OBS records from leeside separation zones are composed of two distinct frequencies, providing field confirmation of scale relations based on flume experiments. The low-frequency spectral signal probably results from wake flapping and the high-frequency signal from vortex shedding. The wake-flapping frequency predominates outside the separation zone and is linked to turbulent structures that suspend sand. Predictions from a depth-scale Strouhal Law show good agreement with measured wake-flapping frequencies. Cross-correlations of OBS records reveal that turbulent sand suspension structures advect downstream at 23–25° above the horizontal. These advection angles are similar to coherent flow structures measured in flumes and to sand suspension structures visualized over large dunes in the field. 相似文献
13.
Theoretical investigation of convective instability in inclined and fluid-saturated three-dimensional fault zones 总被引：2，自引：0，他引：2
Chongbin Zhao B.E. Hobbs A. Ord Shenglin Peng H.B. Mühlhaus Liangming Liu 《Tectonophysics》2004,387(1-4):47-64
The convective instability of pore-fluid flow in inclined and fluid-saturated three-dimensional fault zones has been theoretically investigated in this paper. Due to the consideration of the inclined three-dimensional fault zone with any values of the inclined angle, it is impossible to use the conventional linear stability analysis method for deriving the critical condition (i.e., the critical Rayleigh number) which can be used to investigate the convective instability of the pore-fluid flow in an inclined three-dimensional fault zone system. To overcome this mathematical difficulty, a combination of the variable separation method and the integration elimination method has been used to derive the characteristic equation, which depends on the Rayleigh number and the inclined angle of the inclined three-dimensional fault zone. Using this characteristic equation, the critical Rayleigh number of the system can be numerically found as a function of the inclined angle of the three-dimensional fault zone. For a vertically oriented three-dimensional fault zone system, the critical Rayleigh number of the system can be explicitly derived from the characteristic equation. Comparison of the resulting critical Rayleigh number of the system with that previously derived in a vertically oriented one has demonstrated that the characteristic equation of the Rayleigh number is correct and useful for investigating the convective instability of pore-fluid flow in the inclined three-dimensional fault zone system. The related numerical results from this investigation have indicated that: (1) the convective pore-fluid flow may take place in the inclined three-dimensional fault zone; (2) if the height of the fault zone is used as the characteristic length of the system, a decrease in the inclined angle of the inclined fault zone stabilizes the three-dimensional fundamental convective flow in the inclined three-dimensional fault zone system; (3) if the thickness of the stratum is used as the characteristic length of the system, a decrease in the inclined angle of the inclined fault zone destabilizes the three-dimensional fundamental convective flow in the inclined three-dimensional fault zone system; and that (4) the shape of the inclined three-dimensional fault zone may affect the convective instability of pore-fluid flow in the system. 相似文献
14.
灌区分水口多为直角, 附近普遍存在冲刷、淤积及结构破坏现象。天然河流分、汇流多为锐角, 为探索非直角分水口区域明渠水流紊动特性, 以30°分水角明渠为研究对象, 采用声学多普勒点式流速仪测量各断面上的三维瞬时流速, 分析典型断面上的时均流速、环流强度、紊动强度、紊动能和床面剪切应力分布规律。试验结果显示: 分水口处水流横向流速沿渠宽方向变化较大, 易形成环流, 导致局部冲淤现象明显; 靠近口门侧水流紊动强度变化剧烈且分布无规律, 最大值出现在口门上唇断面; 分水口处下层水体紊动能明显大于上层水体, 紊动能较大值多集中在口门附近; 口门断面下唇附近床面剪切应力较大, 易出现冲刷侵蚀, 破坏渠道稳定; 与直角分水口相比, 分水角为30°时, 泥沙颗粒不易进入侧渠道, 水流对渠底及边壁侵蚀速率较低。研究结果可为灌区渠系设计及运行提供参考。 相似文献
15.
On the north coast of Iceland, the rift zone in North Iceland is shifted about 120 km to the west where it meets with, and joins, the mid-ocean Kolbeinsey ridge. This shift occurs along the Tjörnes fracture zone, an 80-km-wide zone of high seismicity, which is an oblique (non-perpendicular) transform fault. There are two main seismic lineaments within the Tjörnes fracture zone, one of which continues on land as a 25-km-long WNW-trending strike-slip fault. This fault, referred to as the Husavik fault, meets with, and joins, north-trending normal faults of the Theistareykir fissure swarm in the axial rift zone. The most clear-cut of these junctions occurs in a basaltic pahoehoe lava flow, of Holocene age, where the Husavik fault joins a large normal fault called Gudfinnugja. At this junction, the Husavik fault strikes N55°W, whereas Gudfinnugja strikes N5°E, so that they meet at an angle of 60°. The direction of the spreading vector in North Iceland is about N73°W, which is neither parallel with the strike of the Husavik fault nor perpendicular to the strike of the Gudfinnugja fault. During rifting episodes there is thus a slight opening on the Husavik fault as well as a considerable dextral strike-slip movement along the Gudfinnugja fault. Consequently, in the Holocene lava flow, there are tension fractures, collapse structures and pressure ridges along the Husavik fault, and pressure ridges and dextral pull-apart structures subparallel with the Gudfinnugja fault. The 60° angle between the Husavik strike-slip fault and the Gudfinnugja normal fault is the same as the angle between the Tjörnes fracture zone transform fault and the adjacent axial rift zones of North Iceland and the Kolbeinsey ridge. The junction between the faults of Husavik and Gudfinnugja may thus be viewed as a smaller-scale analogy to the junction between this transform fault and the nearby ridge segments. Using the results of photoelastic and finite-element studies, a model is provided for the tectonic development of these junctions. The model is based on an analogy between two offset cuts (mode I fractures) loaded in tension and segments of the axial rift zones (or parts thereof in the case of the Husavik fault). The results indicate that the Tjörnes fracture zone in general and the Husavik fault in particular, developed along zones of maximum shear stress. Furthermore, the model suggests that, as the ridge-segments propagate towards a zero-underlapping configuration, the angle between them and the associated major strike-slip faults gradually increases. This conclusion is supported by the trends of the main seismic lineaments of the Tjörnes fracture zone. 相似文献
16.
脉状金矿成矿控矿构造的研究进展 总被引：2，自引：0，他引：2
综述了国内外脉状金矿床成矿控矿构造的新近研究成果, 认为脉状金矿床的产出大多与遭受挤压作用所造成的地壳缩短机制有关, 与地壳大规模造山作用过程关系密切,主要产于造山带及其边缘;金元素沉淀的构造部位主要是韧性剪切带中的强变形部位、叠加的韧－脆性和脆性裂隙, 低角度断层既是成矿地球化学界面也是重要赋矿构造;含金成矿流体虽然有多种来源,但构造变形过程中的构造动力分异作用是成矿流体的一种重要成因;成矿流体的运移机制主要受断裂构造控制,高角度逆断层作为阀门引起成矿流体压力的周期性变化, 并导致成矿物质结晶与变形呈同步交替发生;值得进一步深入研究和探讨的问题有金成矿与深部构造的关系、低角度断层的成生演化与金成矿物理化学场耦合关系、构造动力变形作用引发含金热液形成的高温高压成矿实验以及韧性剪切带的四维控矿机制等。 相似文献
17.
甘孜－理塘结合带甘孜地区混杂岩类型及成因分析 总被引：1，自引：0，他引：1
对甘孜－理塘结合带甘孜地区的沉积混杂、火山混杂、构造混杂岩作了系统分析研究。重点论述了甘孜地区三条构造混杂岩带的物质组成、变形特征和形成机制。结合带是由大小不等，形态各异的岩块（片）拼贴、堆叠而成的构造混杂岩带。较合理地解释了结合带内，大洋拉斑玄武岩、洋岛玄武岩、大陆碱性玄武岩共存的地质特征。提出了一种新的构造岩石单位——构造混杂岩。并对甘孜地区蛇绿岩的成因作了探讨。 相似文献
18.
塔里木盆地西北缘奥陶系大型古溶洞广泛出露,为古溶洞露头地质建模提供了优越的条件。综合野外资料和Google Earth影像分析,将大型古溶洞以形态结构特征为依据划分成管道—厅堂连通型溶洞、单一管道孤立型溶洞、流线型溶洞3种类型;以存在形式划分成单一溶洞和溶洞群。其中,管道—厅堂连通型溶洞以潜流带型为主,在平面上沿主方位通过岩溶管道连接厅堂分布,厅堂大小不等,在50～50000m3之间变化;单一管道孤立型溶洞以渗流带型为主,平面上呈现单一管道线条状;流线型溶洞分布在潜流带中,从剖面上看呈近圆形、椭圆形和豆荚状等多种形状,包括顺层和斜交地层2种类型。结合各露头剖面中构造、地层条件及发育溶洞类型,明确管道—厅堂联通型溶洞受不整合面控制,分布在三间房、五道班和西克尔剖面中;单一管道孤立型溶洞受断裂系统控制,分布在一间房和硫磺沟剖面中;流线型溶洞主要分布在西克尔剖面,沿溶蚀沟道两侧分布;多种不同因素的耦合控制了溶洞群的分布。以此建立了综合大型古溶洞特征及其控制因素的古溶洞发育概念地质模型,以溶洞群为主要体积计算单元,通过与塔北奥陶系串珠进行体积对比,明确了地质模型的油气勘探意义。 相似文献