开敞式潮滩-潮沟系统发育演变动力机制——Ⅲ.海平面上升影响

为研究海平面上升对潮滩-潮沟系统的影响,以江苏中部粉砂淤泥质海岸为原型,建立变态物理模型,模拟研究在不同海平面潮汐过程作用下的潮沟发育和演变过程,分析了潮滩淹没历时、排水密度、潮沟断面形态等特征参数变化规律。研究表明:潮沟在发育初期伸长速率高于拓宽速率,最终趋于动态平衡;海平面上升后,潮滩淹没历时增加,露滩时间缩短,归槽水对潮沟底床的塑造作用减弱;平均归槽水流长度和Horton排水长度均随海平面上升呈现出减小趋势,潮沟的排水能力增强;潮沟断面宽深比服从对数正态分布,随着海平面上升,潮沟断面面积和宽深比均呈现出增大趋势,宽深比分布范围变广。     

The impact of highly permeable layer on hydraulic system in a coastal aquifer

This study is aimed to understand the hydraulic mechanism of coastal aquifer systems that include highly permeable layers (HPLs). These hydrologic conditions can be found in many volcanic islands that are composed of a series of lava flows discharged into sea or other standing body of water. In the first part, we developed a numerical model based on the geologic and hydrologic data obtained from the eastern Jeju Island, Korea, of which the aquifer contains clinker and hyaloclastite layers. The simulation results reproduced spatial location of fresh‐saline water interface, especially the abrupt decline of interface at the inland part and the thickness variation of transition zone along the cross‐section observed at the eastern Jeju coastal aquifer. We were able to find out that these phenomena are strongly related to the presence of the HPL. In the second part, quantitative analyses were conducted with the use of hypothetical models in order to understand the dynamic characteristics of coastal system that includes HPLs. A series of sensitivity studies were conducted to assess the effect of the horizontal length and vertical depth of HPL on the spatial location of the interface toe and the configuration of transition zone. Various case studies have shown that the seawater intruded into the inland more as the horizontal length of HPL was increased and its vertical depth was decreased. In other simulations including two HPLs, the vertical distance between these two HPLs primarily controlled the flow regime, flux variations, and the configuration of the transition zone. Finally, we performed simulations to evaluate the effect of a rising sea‐level. This study provides more understanding of how the presence of HPL controls the seawater intrusion processes, and the spatial configurations of fresh‐saline water interface at coastal aquifers. Copyright © 2012 John Wiley & Sons, Ltd.     

渤海海域埕岛低凸起东部南区新生代断裂系统及油气分布的控制作用

埕岛低凸起东部南区新生代受控于伸展与走滑作用,断裂构造复杂,传统认为中深层北东向与近东西向断层属于同期同沉积断层。针对这一观点及引起的问题,利用钻井和地震资料,运用构造地质理论解析断裂系统。研究区主要发育正断层、走滑正断层两种类型,断开层位有基底—东营组、平原组—东营组、平原组—基底三种情况,现今断裂以东营组与馆陶组之间的区域不整合面为时限划分为两期断裂系统。早期断裂主要切开基底—东下段,属于同沉积断层;晚期断裂主要切开平原组—东营组,可断达基底,其发育受早期断裂制约。北东向与近东西向断层分别属于早晚两期断裂系统,对油气分布各起关键性控制作用:先期基底升降引起的伸展作用形成北东向断层,控制洼槽地貌与深水重力流沉积环境,发育了连片的层状砂质碎屑流;后期郯庐断裂右行走滑派生了近东西向雁列断层,断层面既充当储层上倾方向的遮挡条件,又在东西向挤压时封闭性变差而变成油气垂向运移通道,断层及断层作用控制了圈闭分布与油气聚集的有序性,自东向西,圈闭及油水界面依次升高且充满度变小,呈全充满、欠充满、半充满等状态。断裂系统研究将地质体置于一定的构造应力场中,分析断层组合的空间排列和交切关系以及断层的力学机制和位移特征等,探究时空演化对油气分布的控制作用。断裂系统研究方法在构造作用叠合区具有适宜性,对该区及类似地区的勘探开发具有现实意义。     

Vegetation change and surface elevation dynamics in estuarine wetlands of southeast Australia

Vertical accretion and surface elevation trends were studied in mangrove and saltmarsh wetlands in southeast Australia. A total of 69 surface elevation tables, each associated with three feldspar marker horizons, was deployed in 10 wetlands across 7 estuaries, and monitored for three years. Saltmarsh and mangrove vegetation distributions were mapped for the same estuaries, and elevation characteristics of the wetlands were modelled. Rates of vertical accretion were found to correlate with tidal range. No relationship was found between rates of vertical accretion and surface elevation increase. A positive relationship was demonstrated between contemporary rates of saltmarsh surface elevation change and longer-term rates of mangrove encroachment into saltmarsh. We conclude that landward mangrove encroachment may be facilitated by local factors contributing to saltmarsh compaction during drought conditions.     

Decadal and seasonal changes in landcover at Padre Island: Implications for the role of the back-barrier in signaling island state change

Long-term and seasonal geomorphological changes at Padre Island, Texas are identified and linked with potential external drivers. Aerial and satellite images from 1950 to 2018, monthly images from 2019 to 2020, and a 2018 LiDAR data set are used to assess long-term and seasonal geomorphological changes within a 50 km² area of Padre Island near Port Mansfield, Texas. Trends in landcover are evaluated by mapping and comparing the relative areal coverage of each facies. Vegetated dunes, absent initially, emerged in the fore-island and expanded into the back-barrier to cover 14% of the study area. The active vegetation-free back-barrier dune field steadily decreased in areal extent from 12% to 6% as vegetation spread. Nebkha dune coverage fluctuated between 4% and 7%. Expansive microbial mats colonized the wind tidal and deflation flats surrounding the vegetated dunes and back-barrier dune field giving rise to a remarkably different landscape over the 50-year period studied. An assessment of external forcing factors identifies increased rates of relative sea level rise and decreased sediment influx as the most likely primary factors driving the geomorphological changes. These changes have induced a widespread shift toward stabilization of island sediments by vegetation and microbial mats, which in turn has starved the back-barrier of sediments resulting in low rates of accretion and increased flooding. These findings highlight the sensitivity of the back-barrier and, in particular, the dune facies to changes in sea level and sediment supply, and show that microbial mats are effective at stabilizing island sediments and may be harbingers to barrier island response to rising sea level. As shown in this study, long-term monitoring of geomorphic facies changes and topography can detect important shifts in the island state that can be used to inform decision making for these sensitive coastal landscapes.     

依据时域、频域信号特征判定桩身完整性类别

通过工程检测实例,结合有关规范以及省组织的专家组对桩基检测结果的验证,论述如何依据时域信号特征和频域信号特征,正确划分桩身完整性的类别。达到减少错判误判的目的。     

Mass rig system for shaking table tests of slender columns

A new mass rig system is proposed to minimize the deficiencies in current shaking table testing setups. This is accomplished by placing the inertial mass on a convex path designed to impose P‐Delta demands on slender cantilever columns. The design and performance of the mass rig system, and the principles used in deriving the equations of motion and their analytical validation against results obtained from shaking table tests, are presented. Formulation of the governing equations of motion was based on Lagrangian mechanics and solved using an implicit linear acceleration method with an adaptive time step formulation. Friction developed in the sliding system was also incorporated in the equations of motion. Experimental results validated the accuracy in the derivation and solution of the equations of motion. Validated by analytical and experimental results, P‐Delta effects were found to increase the displacement demands on slender columns in the low‐frequency range of acceleration input, while in the high‐frequency range P‐Delta effects led to no increase and in some cases even a reduction in displacement demands. Copyright © 2015 John Wiley & Sons, Ltd.     

河北沿海海侵灾害初探

文中以包含海进、海岸侵蚀和海水入侵的广义“海侵”概念,论述河北沿海地区海侵现状及其危害,探讨海侵产生的自然原因和人为活动的影响,在此基础上,评估海侵发展趋势。     

广西沿海超高层建筑进行气象灾害风险评估必要性

通过列举国内外超高层建筑遭受气象灾害的案例,结合广西气象灾害风险区划资料,分析大风、台风、龙卷风、暴雨、雷电（雷击）、强降温等灾害与沿海超高层建筑的关系,以及可能造成的影响和潜在的风险,论述了超高层建筑进行气象灾害风险评估可实现最大安全与最小投资的统一.以期为广西沿海开展“超高层建筑气象灾害风险评估”工作提供理由和依据.     

地震分析软件震相走时表文件结构研究

通过对现有地震分析软件所配置的震相走时表文件的结构类型及优劣进行分析,将震相走时表分为4种组合结构并分析其实用性。在IASPEI91震相走时表文件结构的基础上进行修改、补充和完善,从而提出了一种安全性高、适用面广、灵活性强、能存储各种结构走时表的新型走时表文件结构。应用这种新型结构震相走时表,地震分析软件可以灵活配置不同的走时表,实现精细定位,并为数字化测震台网快速利用测震资料编制和应用高精度的区域震相走时表创造了条件,对于地球深部构造研究具有一定的促进意义。