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21.
1 .IntroductionEvery year ,Taiwanis subjectedtotwo or three typhoonintrusions in average which always causedisasters . Most of the disasters which occur around the coastal zone are due to seabed instability andcoastal structure destruction caused bytyphoo… 相似文献
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Shigehisa Nakamura 《Marine Geodesy》2013,36(4):305-312
A note is presented on tsunami bore front. This tsunami bore front is an old dynamical problem but also a new problem to be understood. The tsunami event on 2004 December 26 has raised this is an urgent problem. The author introduces here a model in order to see a hydrodynamical specific property of the tsunami bore front. This modeling gives us a new understanding about what mechanics is for the interested tsunami bore front, especially, around a coastal zone. This work adds a new understanding about mechanics of water motions as the tsunamis generated by the earthquake undersea at a distant area from the coast. The model in this work points out a specific transitional pattern as a function of time and space of tsunami bore front. This modeling gives what is essential at considering tsunami bore front. 相似文献
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Jinxi Song Guotao Zhang Weize Wang Qi Liu Weiwei Jiang Weiqiang Guo Bin Tang Haifeng Bai Xinyi Dou 《水文研究》2017,31(19):3407-3420
River confluences and their associated tributaries are key morphodynamic nodes that play important roles in controlling hydraulic geometry and hyporheic water exchange in fluvial networks. However, the existing knowledge regarding hyporheic water exchange associated with river confluence morphology is relatively scarce. On January 14 and 15, 2016, the general hydraulic and morphological characteristics of the confluent meander bend (CMB) between the Juehe River and the Haohe River in the southern region of Xi'an City, Shaanxi Province, China, were investigated. The patterns and magnitudes of vertical hyporheic water exchange (VHWE) were estimated based on a one‐dimensional heat steady‐state model, whereas the sediment vertical hydraulic conductivity (Kv) was calculated via in situ permeameter tests. The results demonstrated that 6 hydrodynamic zones and their extensions were observed at the CMB during the test period. These zones were likely controlled by the obtuse junction angle and low momentum flux ratio, influencing the sediment grain size distribution of the CMB. The VHWE patterns at the test site during the test period mostly showed upwelling flow dominated by regional groundwater discharging into the river. The occurrence of longitudinal downwelling and upwelling patterns along the meander bend at the CMB was likely subjected to the comprehensive influences of the local sinuosity of the meander bend and regional groundwater discharge and finally formed regional and local flow paths. Additionally, in dominated upwelling areas, the change in VHWE magnitudes was nearly consistent with that in Kv values, and higher values of both variables generally occurred in erosional zones near the thalweg paths of the CMB, which were mostly made up of sand and gravel. This was potentially caused by the erosional and depositional processes subjected to confluence morphology. Furthermore, lower Kv values observed in downwelling areas at the CMB were attributed to sediment clogging caused by local downwelling flow. The confluence morphology and sediment Kv are thus likely the driving factors that cause local variations in the VHWE of fluvial systems. 相似文献
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基于Copula理论的粗粒土渗透破坏临界水力比降估值 总被引:1,自引:0,他引:1
破坏水力比降是土体渗透稳定性分析和渗流控制的基础。以渗透变形试验为基础,分析了粗粒土临界水力比降与孔隙比、级配不均匀系数和曲率系数间的相关性。利用Copula理论适合建立多个非独立变量间联合分布函数的优点,构造了拟合粗粒土临界水力比降 、孔隙比e、级配不均匀系数 和曲率系数 间相关关系的最优Copula函数,并将其应用于粗粒土临界水力比降估值。结果表明:具有单参数的四维对称Archimedean Copula函数的Nelsen No 6为最优Copula函数。利用构造的最优Copula函数求条件概率,便可得到粗粒土临界水力比降估值的保证率,或者计算在一定保证率条件下临界水力比降估值。通过比较临界水力比降试验值与Copula理论方法、Terzaghi公式及刘杰公式估值,阐述了Copula理论的可靠性,为建立粗粒土临界水力比降与孔隙比及级配特征的多变量统计概率关系及临界水力比降估值提供了一种新途径。 相似文献
25.
蓄能式绳索取心液动潜孔锤钻具是在普通绳索取心钻具总成上端增加了发生和传递冲击载荷的结构,将冲击载荷通过绳索取心钻具外管传递至钻头。新疆达坂城黑沟-达拉地布拉克铀矿工区裂隙、构造蚀变带和构造破碎带发育,地层破碎,使用普通绳索取心钻具钻进,岩心极易堵塞、回次进尺短、频繁打捞内管、钻进效率极低。使用蓄能式绳索取心液动潜孔锤钻具钻进,增加了回次进尺,提高了钻进效率。论文依据施工现场使用情况,介绍了蓄能式绳索取心液动潜孔锤的结构和工作原理,统计、总结了应用情况,论述了绳索取心液动潜孔锤得出的应用结论。 相似文献
26.
Experimental and numerical investigation of groundwater head losses on and nearby short intersections between disc-shaped fractures 下载免费PDF全文
Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computational treatments.The flow velocity has a large spatial differentiation which is more likely to produce non-linear flow and additional head losses on and nearby intersections in such shaped fractures,therefore it is necessary to understand and quantify them.In this study,both laboratory experiments and numerical simulations were performed to investigate the total head loss on and nearby the intersections as well as the local head loss exactly on the intersections,which were not usually paid sufficient attention or even ignored.The investigation results show that these two losses account for 29.17%-84.97%and 0-73.57%of the entire total head loss in a fracture,respectively.As a result,they should be necessarily considered for groundwater modeling in fractured rocks.Furthermore,both head losses become larger when aperture and flow rate increase and intersection length decreases.Particularly,the ratios of these two head losses to the entire total head loss in a fracture could be well statistically explained by power regression equations with variables of aperture,intersection length,and flow rates,both of which achieved high coefficients of determination.It could be feasible through this type of study to provide a way on how to adjust the groundwater head from those obtained by numerical simulations based on the traditional linear flow model.Finally,it is practicable and effective to implement the investigation approach combining laboratory experiments with numerical simulations for quantifying the head losses on and nearby the intersections between disc-shaped fractures. 相似文献
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