长河坝—黄金坪水库区域地震台网监测能力分析     

杜瑶  吴彤  冯薪  丁勇  赵昱  郑昭  王宇玺  王余伟 《地震地磁观测与研究》2020,41(5):25-32

位于四川省甘孜藏族自治州康定市内大渡河干流的长河坝-黄金坪水电站，为大渡河流域开发中，以长河坝、大岗山、瀑布沟等形成主要梯级格局开发方案中，"三库22级"水电站中的第10和11级电站，其地震监测台网也采用梯级设计方式，长河坝-黄金坪上下游水库地震监测台网统一设计、建设及监测，共享同一地震监测能力。通过对监测设备的技术指标、台基地噪声水平和震级-频度对数关系的分析，结果表明，长河坝-黄金坪水库区域地震固定台站建成后，地震监测能力达到并优于设计的理论监测能力，地震监测震级达到下限为M_L 0.5的设计要求。  相似文献   

Numerical Study on Tidal Mixing in the Bohai Sea     

Yifei Zhao  Ting Yu  Hu Wang 《Marine Geodesy》2019,42(1):46-63

The spatial and temporal variability of tidal mixing in Bohai Sea is studied using a numerical approach. In calculating tidal mixing, accurate barotropic tidal current is obtained via a harmonic analysis package utilizing the simulated current output from a high-resolution regional ocean model. And a “small-scale” roughness map is adopted to describe the detailed topographic features of Bohai Sea. It is shown that the tidal mixing estimated in Bohai Sea is much higher than the level of global background, and fluctuates considerably at some regions within a single day. In Liaodong Bay, Bohai Bay and Bohai Strait, the mixing varies greatly, with the peak value of O (10^?2) m² s^?1. The order of magnitude of mixing in Laizhou Bay is about O (10^?5～10^?3) m² s^?1. Mixing with background level of O (10^?5) m² s^?1 only appears in central area. Result also shows that rough topography plays relatively a more important role than tidal current in enhancing diapycnal mixing in Bohai Sea. The distributions of tidal mixing in selected sections reveal that the vertical stratification in Bohai Sea is not obvious, generally renders a barotropic structure.  相似文献   

利用惯容隔震系统的结构层间隔震研究          下载免费PDF全文

张瑞甫  吴明瑞  周方圆  吴应雄  江洁玲 《世界地震工程》2020,(4):008-16

层间隔震技术对于结构竖向不规则以及结构增层等状况有良好的适用性。然而，层间隔震可能出现的较大隔震层变形会带来结构设计的困难。通过在隔震层中设置阻尼元件可以减少变形，但是过大的阻尼出力和过多的数量需求可能导致空间布置和安装不便。惯容元件为解决以上问题提供了一种新的途径。该研究提出采用惯容隔震系统作为层间隔震提高能量耗散效率的手段以控制地震响应，同时也给出了基于性能需求的惯容层间隔震的参数优化设计方法。并以一个标准钢结构模型验证了方法的有效性。结果表明:惯容元件的使用显著降低了上部子结构的地震响应和隔震层的变形，惯容系统实现了预期的耗能增效作用。  相似文献   

双座串联大跨度斜拉桥粘滞阻尼器参数分析          下载免费PDF全文

沈文爱  黄鸣柳  朱宏平  何友娣  张强 《世界地震工程》2020,(4):155-162

以双座串联大跨度斜拉桥-珠海洪鹤大桥为背景，根据桥梁自振特性及场地效应，生成了三组人工波，采用纵向+2/3竖向的地震作用组合输入方式，通过非线性时程分析，系统的研究了粘滞阻尼器对双座串联大跨度斜拉桥减震性能的影响。同时为了确定粘滞阻尼器的最优参数，对粘滞阻尼器的阻尼系数C和速度指数α进行了参数敏感性分析。结果表明:设置纵向粘滞阻尼器能够显著减小双座串联斜拉桥的纵向位移响应，减小主梁在串联处发生碰撞的概率，同时改善主塔塔底结构受力情况，具有良好的耗能减震效果。综合考虑安全性、适用性和经济性等方面，最后给出针对洪鹤大桥的最优粘滞阻尼器参数:速度指数α为0.3，阻尼系数C为3 000kN/（m/s）^0.3。  相似文献   

Deposition and preservation of fluvio-tidal shallow-marine sandstones: A re-evaluation of the Neoproterozoic Jura Quartzite (western Scotland)     

Bruce K. Levell  Howard D. Johnson  Daniel S. Collins  Marijn van Cappelle 《Sedimentology》2020,67(1):173-206

The 2 to 5 km thick, sandstone-dominated (>90%) Jura Quartzite is an extreme example of a mature Neoproterozoic sandstone, previously interpreted as a tide-influenced shelf deposit and herein re-interpreted within a fluvio-tidal deltaic depositional model. Three issues are addressed: (i) evidence for the re-interpretation from tidal shelf to tidal delta; (ii) reasons for vertical facies uniformity; and (iii) sand supply mechanisms to form thick tidal-shelf sandstones. The predominant facies (compound cross-bedded, coarse-grained sandstones) represents the lower parts of metres to tens of metres high, transverse fluvio-tidal bedforms with superimposed smaller bedforms. Ubiquitous erosional surfaces, some with granule–pebble lags, record erosion of the upper parts of those bedforms. There was selective preservation of the higher energy, topographically-lower, parts of channel-bar systems. Strongly asymmetrical, bimodal, palaeocurrents are interpreted as due to associated selective preservation of fluvially-enhanced ebb tidal currents. Finer-grained facies are scarce, due largely to suspended sediment bypass. They record deposition in lower-energy environments, including channel mouth bars, between and down depositional-dip of higher energy fluvio-ebb tidal bars. The lack of wave-formed sedimentary structures and low continuity of mudstone and sandstone interbeds, support deposition in a non-shelf setting. Hence, a sand-rich, fluvial–tidal, current-dominated, largely sub-tidal, delta setting is proposed. This new interpretation avoids the problem of transporting large amounts of coarse sand to a shelf. Facies uniformity and vertical stacking are likely due to sediment oversupply and bypass rather than balanced sediment supply and subsidence rates. However, facies evidence of relative sea level changes is difficult to recognise, which is attributed to: (i) the areally extensive and polygenetic nature of the preserved facies, and (ii) a large stored sediment buffer that dampened response to relative sea-level and/or sediment supply changes. Consideration of preservation bias towards high-energy deposits may be more generally relevant, especially to thick Neoproterozoic and Lower Palaeozoic marine sandstones.  相似文献   

圆筒型FPSO优化设计与水动力性能分析     

赵治民  李焱  唐友刚  何鑫  童波 《海洋工程》2020,38(1):11-19

针对圆筒型海上储油装置FPSO垂荡运动性能较差、无法安装干式井口的问题,设计了带延伸筒体与矩形阻尼结构的圆筒型FPSO,根据延伸筒体与矩形阻尼结构是否通海分为两种型式。建立水动力计算模型,比较分析不同延伸筒体和阻尼结构型式对FPSO水动力性能的影响。针对南海作业海域,设计了悬链式系泊系统,基于JONSWAP波浪谱对FPSO的运动进行时域预报,并对系泊系统进行校核。分析结果表明:通海型FPSO垂荡固有周期显著提升,可以错开南海百年一遇谱峰周期,通海型FPSO满足钻井、安装干式井口的运动响应要求,系泊系统系缆张力满足规范要求。  相似文献   

潮汐和风对马六甲海峡海流的影响     

范锦晓  胡松 《热带海洋学报》2020,39(4):13-24

基于非结构有限体积法海洋模型FVCOM(Finite-Volume Community Ocean Model), 建立了马六甲海峡及其毗邻海域高分辨率水动力数值模型, 研究了风和潮流作用下的余环流结构以及水体输运特征。结果表明, 马六甲海峡航道中央潮流运动以往复流为主, 边缘存在旋转流; 主要研究区域内落潮流速略大于涨潮流速, 东南窄道处流速最大; 因峡道束窄变浅, 在涨落潮过程中潮流发生汇聚与分离; 主要研究区域东南段存在3个显著的潮致余环流; 东北季风驱动时模型响应为海峡海流整体向西北方向流动, 西南季风时反之; 季风期间潮致表层余环流结构被破坏, 但底层余流仍存在水平环流结构, 且随着风速增加, 底层余环流的数目、大小、形状、位置均会产生变化; 季风过渡期余环流结构也会发生部分改变, 尤其是小潮期间风场影响效果显著。  相似文献   

On the morphology of radial sand ridges     

Weina Zhang  Xiaohe Zhang  Huiming Huang  Yigang Wang  Sergio Fagherazzi 《地球表面变化过程与地形》2020,45(11):2613-2630

We use a hydrodynamic model applied to an idealized fan-shaped basin to explore the morphology and dynamics of radial sand ridges in a convergent coastal system. A positive morphological feedback between channel incision and flow redistribution is responsible for the formation of the channel-ridge pattern. The selection mechanism of bottom wavelength is associated with flow concentration in the deeper part of the channels. Our results are compared to sediment and hydraulic dynamics in the radial sand ridges (RSRs) in China. In a convergent, sloping basin the tangentially averaged tidal velocity peaks at 47 km from the apex. This distance is similar to the arc distance, 62 km, where the RSRs are most incised. An offshore shift in tidal phase results in stronger flows near the north coastline, explaining the presence of asymmetric channel patterns. A numerical stability analysis indicates that small radial oscillations with a wavelength of 10° to 15° maximize the velocity in the troughs. This oscillation wavelength also emerges in the RSRs, which display a peak in spectral energy at a radial wavelength between 25° to 37.5°. High-resolution numerical simulations in the RSRs confirm that flow concentration occurs in the deeper part of the channels, keeping them flushed. We therefore conclude that the RSRs display morphometric characteristics similar to other tidal incisions, like tidal inlets and intertidal channels. This result further supports the dominant role of tidal prism and related peak velocities in incising coastal landscapes. © 2020 John Wiley & Sons, Ltd.  相似文献   

关于土层地震反应分析中阻尼矩阵建模方式的讨论          下载免费PDF全文

殷琳  楼梦麟  康帅 《世界地震工程》2019,35(2):132-140

阻尼矩阵的选择对土层时域内地震反应计算的准确性有重要意义。本文构造了质量比例阻尼、刚度比例阻尼、Rayleigh阻尼、Caughey阻尼和Clough阻尼矩阵，研究各阻尼对土层地震反应分析精度的影响。以苏通大桥5号桥塔基础处的工程场地为例，分别以人工合成基岩波，Northridge波、Parkfield波和汶川波为输入，得到不同阻尼模型下土层的地震反应，结果表明Clough阻尼在计算精度和误差稳定性上要优于其他阻尼模型，针对Clough阻尼的不足之处提出了改进方法，算例表明改进后的Clough阻尼能在保证计算精度的前提下减少计算机的存储量和计算量。  相似文献   

铜川新区黄土与古土壤动剪切模量比和阻尼比的统计研究          下载免费PDF全文

段蕊  陈党民 《世界地震工程》2019,35(3):153-160

利用铜川市地震小区划项目的大量典型土样动三轴试验结果，采用双曲线模型拟合得到了铜川新区黄土和古土壤在8个典型应变下的动剪切模量比和阻尼比值。根据不同沉积年代和不同土层深度2种方法对黄土、古土壤动剪切模量比和阻尼比随剪应变变化情况进行了统计和对比分析。研究发现:同一剪应变下，黄土、古土壤动剪切模量比随沉积年代和土层深度的增加而增加。二者对黄土动剪切模量比的影响较为显著。  相似文献