大跨度钢板桩围堰的形变分析与预报

结合武汉市东湖隧道工程中大跨度钢板桩围堰的变形监测数据,对大跨度钢板桩围堰的形变特征及预测模型进行了研究,针对其大量级、强趋势和波动性的数据特点,探索出与之相适应的高精度、高稳定的单项与组合预测模型,并采用Matlab编制相应的实用预测软件,获得了良好的预测效果。可为今后同类工程大跨度钢板桩围堰的形变分析预测提供有益借鉴。     

The Linkage between Midwinter Suppression of the North Pacific Storm Track and Atmospheric Circulation Features in the Northern Hemisphere

The midwinter suppression(MWS) of the North Pacific storm track(NPST) has been an active research topic for decades. Based on the daily-mean NCEP/NCAR reanalysis from 1948 to 2018, this study investigates the MWS-related atmospheric circulation characteristics in the Northern Hemisphere by regression analysis with respect to a new MWS index, which may shed more light on this difficult issue. The occurrence frequency of the MWS of the upper-tropospheric NPST is more than 0.8 after the mid-1980 s. The MWS is accompanied by significantly positive sea-level pressure anomalies in Eurasia and negative anomalies over the North Pacific, which correspond to a strengthened East Asian winter monsoon. The intensified East Asian trough and atmospheric blocking in the North Pacific as well as the significantly negative low-level air temperature anomalies, lying upstream of the MNPST, are expected to be distinctly associated with the MWS. However, the relationship between the MWS and low-level atmospheric baroclinicity is somewhat puzzling.From the diagnostics of the eddy energy budget, it is identified that the inefficiency of the barotropic energy conversion related to the barotropic governor mechanism does not favor the occurrence of the MWS. In contrast, weakened baroclinic energy conversion, buoyancy conversion, and generation of eddy available potential energy by diabatic heating are conducive to the occurrence of the MWS. In addition, Ural blocking in the upstream region of the MNPST may be another candidate mechanism associated with the MWS.     

大跨预应力混凝土空间框架结构的地震振动台试验研究

利用地震振动台对大跨预应力混凝土井式梁空间框架结构的抗震性能进行了实验研究。两个模型的实验结果表明：(1)大跨预应力井式梁空间框架结构可以提供大的楼层平面内刚度；(2)对称大跨预应力井式梁空间框架结构，可以不考虑耦合地震反应；(3)大跨预应力井式梁空间框架结构的竖向地震反应中心大而周边小；(4)在相同加速度但不同的地震波作用下，结构的竖向地震反应不同。     

腾冲火山区剪切波和尾波衰减初步研究

用云南腾冲火山地区观测的地震数字化记录进行了尾波和剪切波的衰减测量。用AkiandChouet和Sato单次散射模型获得 5 2秒和 18秒流逝时间尾波的品质因子分别为Qc (f) =5 7×f- 0 94和Qc (f) =2 6×f- 0 95 ,表明地壳上部和地壳上地幔的地震波衰减频率变化率一致。两者均未显示出活火山地区尾波衰减的异常特征。尾波掠过空间椭球的平均半轴 ,前者约为 80km ,大大超出了腾冲火山分布的地理范围 ,后者约为 30km ,在腾冲火山分布的地理范围之内。用尾波规一双台S波振幅比法进一步缩小所用地震波掠过的空间 ,最后获得了S波随频率的衰减有类似于前人报导的活火山地区尾波频率衰减的特征 :相对于低频 (1 5～ 6Hz) ,高频 (6～2 0Hz)的Q- 1s 变化很小。从地表位置看 ,腾冲最年青的全新世的马鞍山和老龟坡火山就在S波掠过范围内 ,打鹰山火山也在近旁。这一结果表明在这三座火山体之下存在低速高衰减体。火山或处于休眠状态 ,或在消亡过程之中。     

丽江大研镇震灾分布和地脉动测量结果之间的相关性

丽江７．０级地震后，大研镇被毁建筑物的地理分布呈显４条条带，伤亡人员的地理分布和上述条带重合。９１个短周期地脉动测点的观测资料表明，分布在上述条带内的大多数测点，其卓越周期大于０．３Ｓ；条带外的测点，其卓越周期一般在０．１Ｓ左右。作认为卓越周期和烈度异常之间良好的相关性，是因为地脉动卓越周期和地方震的频谱之间存在良好的相关性。     

Mesozoic paleogeography and tectonic evolution of South China Sea and adjacent areas in the context of Tethyan and Paleo-Pacific interconnections

Abstract   During the Mesozoic era, the South China Sea and its environs were located at the south-eastern margin of the Eurasian continent. There has been hot debate on the influences of Tethyan and Paleo-Pacific tectonics to the Mesozoic evolution of the area. This paper compiles lithofacies maps of six time slices and discusses the paleogeographic and tectonic evolution of the area based on this compilation and other data on structural deformation and magmatism. In the Early Triassic, the Paleotethys Ocean extended eastward to the study area through the Song Da passage. Then a significant east–west differential evolution began. In the Late Triassic, the western area uplifted as a result of the collision between the Indosinian and South China blocks during the Indosinian orogeny, and the Song Da passage has closed since then. Meanwhile, a transgression of Paleo-Pacific waters occurred in the eastern and south-eastern portions of the area, forming the 'East Guangdong–North-west Borneo Sea'. In the Early Jurassic, seawater transgression was even more pronounced, resulting into the connection of this sea with the Mesotethys Ocean to the west. Large quantities of Tethyan water carrying Tethyan organisms entered the area. In the Middle Jurassic, a short-lived transgression occurred in the eastern Mesotethys and resulted in the formation of the 'Yunnan–Burma Sea'. The Late Jurassic to Early Cretaceous was the climax of the subduction of both the Mesotethys and Paleo-Pacific towards the Eurasian continent. This led to the formation of the great 'Circum South-east Asia Subduction–Accretion Zone' in the Middle or Late Cretaceous. This paper also presents various lines of evidence for a newly recognized segment of this Mesozoic subduction–accretion zone buried under Cenozoic sediments in the north-eastern South China Sea.     

Tectono-thermal modeling of the Yinggehai Basin,South China Sea

Based on the observed data, the average value of surface heat flow in the Yinggehai Basin is calculated and it turns out to be 84.1 mW/m². The thermal evolution of the basin since the Cenozoic era has been attempted by tectono-thermal modeling. Three-phase extension made the basin become hotter and hotter, reaching its climax in paleo-temperature history since 5.2 Ma. And nowadays, the basin is in the heat flow decreasing period. During the Cenozoic era, the basement heat flow remained at 50–70 mW/m² all the time. This is related to the degree of each extension phase, stretching rate mode and also the limited basin scale. Modeling results also show that, the surface heat flow is controlled mainly by the basement heat flow, and less than 20% comes from radiogenic heat production in the sediments of the basin     

地下水稳定运动基本微分方程的三维解法──地下水向承压完整井的运动

以映射和叠加原理为基础，探讨了均质、等厚承压含水层中地下水向完整井作三维运动时，地下水稳定运动基本微分方程的求解方法，并与裘布衣公式作了对比。由于求解时考虑了地下水流速的水平、垂直分量，故所得结果较裘布衣公式更为准确与合理。     

基于Landsat数据的近30年上海大陆岸线变化分析

为了研究上海大陆岸线的最新变化,以5年为间隔,选取1988~2019年间的近30年多期Landsat遥感影像,采用多尺度分割和光谱分割相结合的分割方法,提取影像中研究区域的水边线,并利用同年不同时相的水边线和平均大潮高潮位数据进行潮位校正,获取相对准确的海岸线位置。使用线性回归速率方法(LRR)对大陆岸线的外扩距离和速度变化进行了统计,同时对上海大陆岸线长度和面积的时空变化进行了分析。结果表明,从1988~2019年,上海大陆岸线总长度增加了10.4km,增幅达5.19%,长度变化呈“减增减”的趋势。海岸线的平均外扩距离为1.35km,平均LRR值为50m/年,外扩距离最大处位于南汇嘴。上海大陆沿岸总的新增土地总面积达到220.39km²。     

湖盆扇三角洲河口坝发育程度及粒度韵律特征:以滦平盆地桑园剖面下白垩统西瓜园组为例*

扇三角洲作为重要的油气储集场所,其成因单元类型及分布特征控制着油气的差异分布及采出效率。关于扇三角洲分流河道沉积特征已有共识,但河口坝沉积特征尤其是韵律特征尚存在争议。以滦平盆地桑园剖面下白垩统西瓜园组湖盆扇三角洲沉积体为例,通过人工实测及无人机观测相结合的方法,对河口坝沉积特征、尤其是韵律特征进行研究,利用水槽模拟实验阐明河口坝韵律特征的形成机理。结果表明,河口坝在整个剖面中占砂(砾)岩体的45.27%,分流河道和席状砂分别占53.42%和1.31%。河口坝在剖面上呈底平顶凸状,通常由多期增生体组成。当增生体主要由砂岩组成时,呈粒度反韵律特征; 而当增生体主要由砾岩组成时,呈粒度正韵律特征。河口坝整体韵律受控于增生体的垂向叠置样式,既可呈反韵律特征又可呈正韵律特征。当流量、沉积底形坡度等地质条件一定时,河口坝内部增生体韵律性主要受沉积物粒度控制。当沉积物粒度较细时,河口水流扩散模式为底床摩擦力主控,增生体呈现反韵律特征; 而当沉积物粒度较粗时,河口水流扩散模式为惯性力主控,河口坝增生体则呈现正韵律特征。