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161.
Physically based modeling approach has been widely developed in recent years for simulation of dam failure process resulting
from overtopping flow. Due to the lack of field data, there exist few applications to natural quake dams with complex erosion
mechanisms. This paper presents a physically based simulation of the failure process of the Tangjiashan Quake Dam formed as
a result of the “May 12, 2008” Wenchuan earthquake in China. The one-dimensional model adopted features as cost saving but
enables capturing the main characteristics of the failure process, where selective sediment transport and gravitational slope
collapse are accounted for. The simulated flow hydrograph and breach progression process are generally in good agreement with
the observed data. Unsteadiness and non-uniformity are found to be substantial characteristics of breach progression during
the failure process of natural quake dams. Sensitivity analysis showed that the Manning resistance coefficient and the erodibility
coefficient in Osman and Thorne’s (J Hydraul Eng 114(2):134–150, 1988) model significantly influences the flow peak discharge but has less influence on its occurrence time, while the velocity
lag coefficient associated with bed-load transport may affect the two breaching parameters substantially. 相似文献
162.
华北强烈地震深部构造环境的探测与研究 总被引:5,自引:1,他引:5
20世纪六七十年代以来, 华北地区发生了一系列强烈地震. 强烈地震的孕育、 发生和发展与深部构造密切相关. 近50年来, 我国地震科学领域在强烈地震的地震构造和深部环境方面开展了大量的研究. 深部地球物理探测和地震层析成像结果揭示了华北地区地壳结构的基本特征, 并在强烈地震发生的深部构造环境等问题上取得了重要进展. 本文在回顾华北地区地壳上地幔结构探测的基础上, 对1966年邢台MS7.2, 1976年唐山MS7.8, 1975年海城MS7.3和1679年三河—平谷M8.0地震的地震构造和深部构造环境进行评述. 深部地球物理数据的综合分析表明, 震源下方的低速异常带, 高角度超壳深断裂, 地壳深浅构造的不一致, 偏低的上地幔顶部速度和局部隆起的莫霍界面, 是华北伸展构造区深部孕震环境的共同特征. 相似文献
163.
根据2018年秋季至2019年夏季4个季节的海滩剖面形态测量和表层沉积物粒度分析结果,研究了海阳万米海滩地形和表层沉积物粒度季节变化特征,探讨了控制研究区砂质岸滩季节性演化的因素。结果表明:连理岛-东村河口以西海滩剖面形态在强动力和弱动力条件下分别呈“上蚀下淤”和“下冲上塑”特征,夏季台风造成的滩肩侵蚀量大于冬季风,在滩面形成的沙坝数量多、规模小且离岸距离较之冬季风更远。连理岛-东村河口处海滩剖面形态整体呈淤积状态,且在强动力条件下的淤积量大于弱动力条件。连理岛-东村河口以东海滩剖面形态的季节性变化幅度小于以西海滩,同时滩肩顶剖面形态在夏季出现明显下凹特征。表层沉积物粒度特征变化同样呈现东西差异的特点,秋季到冬季,西侧海滩表层沉积物粒度变粗、分选变差,而东侧海滩变细、分选基本不变;冬季到春季,海滩表层沉积物粒度总体变细、分选较好;夏季变化趋势与冬季相似,但变化幅度有所差异。人工岛和港口等海岸工程建设是导致海滩剖面形态和表层沉积物粒度东西差异的主导因素;波浪和台风事件等是控制砂质岸滩季节性演化的主要动力因素;潮汐作用、旅游开发等人类活动也对岸滩演化造成一定影响。 相似文献
164.
An analytical method is developed to study the sheltering effects on arc-shaped floating perforated breakwaters. In the process of analysis, the floating breakwater is assumed to be rigid, thin, vertical, and immovable and located in water with constant depth. The fluid domain is divided into two regions by imaginary interface. The velocity potential in each region is expanded by eigenfunction in the context of linear theory. By satisfying continuity of pressure and normal velocity across the imaginary fluid interface, a set of linear algebraic equations can be obtained to determine the unknown coefficients for eigenfunction expansions. The accuracy of the present model was verified by a comparison with existing results for the case of arc-shaped floating breakwater. Numerical results, in the form of contour maps of the non-dimensional wave amplitude around the breakwater and diffracted wave amplitude at typical sections, are presented for a range of wave and breakwater parameters. Results show that the sheltering effects on the arc-shaped floating perforated breakwater are closely related to the incident wavelength, the draft and the porosity of the breakwater. 相似文献
165.
冕洞的研究在近二十多年里取得了丰硕的成果。本文回顾了冕洞的发现及观测历史,系统阐述了冕洞的结构特征、形成及演化规律,讨论了冕洞对日地空间产生的影响,冕洞与超级活动区的关系以及冕洞在太阳活动预报中所起的作用,在此基础上利用1970—1995年的冕洞资料对冕洞的时空分布和磁极性演化规律与太阳活动周的关系,以及冕洞与太阳风速度、地磁扰动等方面进行分析研究,得出以下结论:(1)冕洞在南北半球的分布在形态上基本是对称的,但在冕洞数量上北半球稍占优势;(2)冕洞的盛衰演化呈周期性,表现为赤道冕洞周期与黑子周期是完全一致的,极冕洞周期与黑子周期相位相差180°;(3)赤道冕洞的纬度分布随太阳活动周上升而上升,当太阳活动周达到极大值时,它也达到极大,然后再随太阳活动周下降而下降,极冕洞的纬度延伸方向演化与赤道冕洞相反;(4)极冕洞的极场呈11年周期性,并且极场反转出现在太阳活动峰年期间;(5)太阳风和地磁扰动与冕洞的演化有着密切的关系 相似文献
166.
167.
采用了单柱离子色谱法测MnO2产品中无机离子杂质;提出了消除干扰的可行途径,将La(OH)3加入后能同时消除进样峰的干扰和溶剂峰的出现。选用1.75mmol/L邻苯二甲酸1.75mmol/L三羟甲基氨基甲烷为混合淋洗剂测定F^-,Cl^-,NO3^和SO^2-4,其标准加入回收率为95%-105%;RSD(n=7)为2.47%-8.08%。 相似文献
168.
海上固定平台的冰激振动响应计算与分析 总被引:6,自引:0,他引:6
本文用强迫振动理论计算了辽东湾常见冰情挤压冰作用下JZ20—2—1采油平台和测冰平台的自振特性、位移、速度和加速度响应以及平台的应力响应,取得了一些有意义的结果,供平台设计和使用时参考。 相似文献
169.
Jack-up units are extensively playing a successful role in drilling engineering around the world, and their safety and efficiency take more and more attraction in both research and engineering practice. An accurate prediction of the spudcan penetration depth is quite instrumental in deciding on whether a jack-up unit is feasible to operate at the site. The prediction of a too large penetration depth may lead to the hesitation or even rejection of a site due to potential difficulties in the subsequent extraction process; the same is true of a too small depth prediction due to the problem of possible instability during operation. However, a deviation between predictive results and final field data usually exists, especially when a strong-over-soft soil is included in the strata. The ultimate decision sometimes to a great extent depends on the practical experience, not the predictive results given by the guideline. It is somewhat risky, but no choice. Therefore, a feasible predictive method for the spudcan penetration depth, especially in strata with strong-over-soft soil profile, is urgently needed by the jack-up industry. In view of this, a comprehensive investigation on methods of predicting spudcan penetration is executed. For types of different soil profiles, predictive methods for spudcan penetration depth are proposed, and the corresponding experiment is also conducted to validate these methods. In addition, to further verify the feasibility of the proposed methods, a practical engineering case encountered in the South China Sea is also presented, and the corresponding numerical and experimental results are also presented and discussed. 相似文献
170.
Geophysical methods were applied for hydrogeological targets in many countries including Vietnam. This paper presents results of using complex geophysical techniques as well as 2D electrical resistivity imaging (ERI), vertical electrical sounding (VES), very low frequency (VLF), and seismic refraction for geological structure investigation for locating the aquifers and assessing the hydrogeological conditions for groundwater potential in industrial zones of North Hanoi, Vietnam. The locations of two aquifers are determined by their depth and thickness on the basis of resistivity and seismic velocity values which were proved by stratifications of three boreholes to 40–60 m of depth on the study area. There are connections from surface water to shallow aquifer by hydraulic windows, as follows from VLF data. The deeper aquifer can be considered as a potential groundwater supply, but the water level is descending in time, as shown by hydrological monitoring. However, with careful use and by reducing sources of pollution, groundwater can continue to be an important natural resource for future. 相似文献