小南海水库地震堰塞坝渗漏特征研究   总被引：7，自引：0，他引：7  

王子忠  杨绍平 《四川地质学报》2003,23(1):26-30

从病害整治的角度论述了小南海水库地地震堰塞坝坝体本构特征，渗漏及渗透稳定、防渗处理措施等，并介绍了渗流量计算的解析法与系统理论法。  相似文献   

河南新郑枣区土壤地球化学研究   总被引：3，自引：0，他引：3  

侯海燕  赵敬红  马宏卫  李诗言  张洪  韩存强 《地球化学》2006,35(2):194-200

对比研究了地球化学景观环境、第四系、成土母质和土壤等的地球化学特征与新郑枣品质和产量的关系。研究表明,覆砂的岗丘是优质新郑枣适生的地球化学环境。典型的地质背景、第四系沉积物组构、成土母质和土壤等综合生态地球化学要素影响了新郑枣的品质和产量。区内中上更新统中发育古土壤层,是枣树生产期有益元素聚集的地球化学障和潜藏的有益元素的地球化学库,在某种程度上决定了枣的品质和产量。本区土壤和土体中多种有益营养元素含量偏低,处于缺乏状态。  相似文献   

Wave run-up on a fixed surface-piercing square column using multi-layer barrier     

《Applied Ocean Research》2018

Steep or breaking waves may produce critical run-ups on a surface-piercing column, as represented by an unexpectedly high uprush, which has the potential of generating damaging localised wave-in-deck loads. Hence, to improve the air gap performance of offshore column-stabilised platforms, this paper proposes the mounting of an innovative multi-layer barrier on the column surface at a certain distance below the lower deck. Experiments were performed using a truncated square column to examine the performances of different versions of the barrier, namely, solid-plate, porous-plate, and intermittent-plate types, under four different focused waves. All the barrier types were found to obstruct and deflect uprush flow under storm conditions. However, the solid-plate type tended to experience considerable wave forces, with its impermeability also rendering the higher layers ineffective. The intermittent-plate type dissipated the uprush flow and decreased the wave impact, although it exhibited relatively strong flow disengaging, which decreased the efficiency under large wave run-ups. Conversely, the porous-plate type exhibited adequate performance, with a larger plate porosity and moderately high mounting elevation tending to improve the uprush obstruction performance and further decrease the wave slamming loads. A barrier with an appropriately designed plate porosity, number of layers, and mount elevation is expected to perform efficiently under severe sea states, providing protection for the lower deck against extreme wave run-ups.  相似文献   

The formation and closure of the Big Breach of Sacalin spit associated with extreme shoreline retreat and shoreface erosion     

Florin Iulian Zăinescu  Alfred Vespremeanu-Stroe  Florin Tătui 《地球表面变化过程与地形》2019,44(11):2268-2284

We document a case of exceptionally large natural breaching of a sandy spit (Sacalin spit, Danube Delta) using multiannual to seasonal surveys of topography and bathymetry on successive cross-barrier and shoreface profiles, LiDAR data, satellite imagery, and wind and wave data. The large breach, which quickly reached 3.4 km in May 2014, is attributed to morphological preconditioning of the narrow (50–150 m) barrier, which was susceptible to breaching even during moderate storm conditions. The event switched the barrier's decadal evolution from low cross-shore transport to high cross-shore transport over the barrier, which is an order of magnitude larger than during the non-breach period. Upper shoreface erosion, as indicated by the extensive erosion down to −4 m, indicates that this zone is a significant source for the rebuilding of the barrier. Barrier recovery and widening trigger a negative feedback which limits the back-barrier sediment transfer. As a result, back-barrier deposition decreases whilst the barrier aggradation through overwash becomes more frequent. The Big Breach (TBB) closed naturally in three years. The very high deposition rate of sediment in the breach is a testimony of the high sediment volumes supplied by the longshore transport and the high sediment released through shoreface retreat, and resulted in widening the barrier to a maximum of 1 km. Since the newly-formed barrier shoreline retreated 500 m, this reveals that barrier breaching is an important mechanism which significantly accelerates the landward migration of the barrier system and is a proof of the highly non-linear morphodynamics involved in the barrier island translation. © 2019 John Wiley & Sons, Ltd.  相似文献   

轨道交通典型隔振屏障隔振效果模型试验研究     

刘晶磊  张瑞恒  赵晓玉  刘恒  赵倩  王奥运 《地震工程与工程振动》2019,39(1):231-241

为了研究轨道交通中几种典型隔振屏障的隔振效果,本文通过室外模型试验,以振动加速度级作为振动评价标准,对其做出分析并给出相应评价。结果表明:(1)土体振动主要是由中低频振动波引起的;(2)对比分析几种典型连续隔振屏障的隔振效果:空沟>地下连续墙>碎石填充沟>橡胶填充沟;综合考察几种非连续隔振屏障得出:混凝土桩的隔振效果优于隔振井;隔振效果优劣比较为:混凝土实心桩>混凝土空心桩>PVC空井>碎石填充井>橡胶填充井;(3)对于单排混凝土空心桩,空心率越大,隔振效果相对越差;空心桩内部形状的改变对隔振效果影响不大,外部形状的改变对隔振效果有一定程度影响,但效果不显著,且桩体外截面为方形时的隔振效果较圆形差。  相似文献   

二维地基中空沟−波阻板联合隔振屏障分析     

周凤玺  马强  周志雄 《岩土力学》2020,41(12):4087-4092

针对地基隔振控制,提出了一类新型的空沟?波阻板联合隔振屏障,并对其隔振性能进行了数值分析。首先,利用复伸展坐标变换,在频域内建立了完全匹配层（perfect matched layer, PML）吸收边界的控制方程;其次,利用Galerkin近似技术,给出了以位移为基本未知量的二阶非分裂格式PML的频域有限元计算列式;最后,通过数值算例分析了空沟?波阻板联合隔振屏障的物性参数（地基与波阻板的模量比）、几何参数（空沟深度、波阻板深度）以及载荷参数（振动波频率）等对其隔振性能的影响规律。结果表明,空沟?波阻板联合隔振屏障结合了空沟和波阻板各自的优势,可以有效地控制不同频率振源引起的地基振动。  相似文献   

孟加拉湾障碍层年际变化及其与印度洋偶极子事件的联系   总被引：1，自引：1，他引：0  

郭文仪  邱云  林新宇 《海洋学报》2020,42(9):38-49

利用1980?2015年SODA温盐资料,结合Argo数据分析了印度洋偶极子(IOD)事件年份孟加拉湾障碍层的变化特征及其形成机制。结果表明,IOD事件年份孟加拉湾障碍层变化显著。纯的正IOD(纯pIOD)年份及伴随型pIOD年份盛期(9?11月),除孟加拉湾内西南海域障碍层厚度略变厚约5 m外,赤道海域、安达曼海至孟加拉湾北部障碍层厚度均变薄5～15 m,此障碍层距平盛期形态在纯pIOD年份随pIOD消亡迅速消退,但在伴随型pIOD年份维持至翌年3?5月才开始弱化。纯的负IOD (纯nIOD)年份障碍层厚度变化特征与pIOD年份大体相反。进一步分析表明,IOD事件年份赤道风场距平的远地强迫造成等温层深度的变化是湾内障碍层变化的主因。在伴随型IOD年份,受ENSO事件的影响,赤道风场距平在IOD消亡后仍得以维持3个月以上,使得湾内障碍层距平形态持续更久。除赤道远地强迫外,湾内局地风场的Ekman抽吸作用以及混合盐度变化对障碍层厚度年际变化也有一定影响。  相似文献   

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田颜锋  李姗姗  刘晓刚  付国峰 《大地测量与地球动力学》2009,29(6):130-132

???????????????????o???????????????????????FIR??????????????????????????FIR????????????о??????????λ?????????????????????????????????????????????о?????????????????????任?е????Ч???  相似文献   

黄土高原现代自然降尘的特征——以固原安塞为例     

梁剑鸣  周杰  何忠  刘卫国  梁银丽  程积民 《海洋地质与第四纪地质》2009,(1)

收集了宁夏固原2007年5月至2008年4月的12个降尘样品,陕西安塞2007年5—8月、2008年3—11月的13个降尘样品,并分别在两个降尘采样点附近采集了2个自然表土样品,对样品进行了总有机碳、粒度、磁化率分析,结果发现两地降尘的总有机质含量在1.029%～6.634%之间。粒度特征显示近源搬运占主导地位,同时,工业污染产生的PM10以下颗粒物贡献较小。降尘磁化率比自然表土明显偏高,但季节变化不明显。  相似文献   

The use of fractal geometry to determine the impact of inlet migration on the dynamics of a seagrass landscape     

A.H. Cunha  R.P. Santos 《Estuarine, Coastal and Shelf Science》2009,84(4):584-590

The use of fractal geometry to evaluate seagrass scaling behavior and the persistence of seagrass landscape patterns in relation to a disturbance is presented in this paper.Ria Formosa is a dynamic barrier-island system with a migrating inlet that creates a cyclic disturbance in a seagrass landscape. Seagrass patches which develop in the intertidal and shallow subtidal areas of Ria Formosa were digitized from a temporal sequence of aerial photographs, from 1980 to 1998. The methodology used to evaluate seagrass scaling behavior was proposed by Meltzer and Hastings (1992), and relates the frequency distribution of patch size with the existence of patch size-related patterns. The Hurst exponent was calculated to assess the temporal persistence of the seagrass landscape. Univariate regression was used to investigate relations between temporal persistence and disturbance. The existence of patch size-related patterns was identified for all years suggesting shifts in generating processes occurring at different domains of scales in the seagrass landscape. The results enforces the idea that it is important to recognize the existence of diverse processes occurring at different domains of scales and, emphasizes the importance of evaluating issues of temporal and spatial scale while trying to understand changes in seagrass landscapes. The Hurst exponent estimates show that although the migration and relocation of the inlet affected this system the evolutionary trajectory of the seagrass landscape is persistent, i.e., the patch dynamics observed is stable. Furthermore, persistence values were different for differently sized patches, small patches having lower persistence then larger patches.  相似文献