环礁沉积体系的过程-产物关系: 勘察式模拟初探

海洋沉积体系的定量模拟可分为仿真和勘察式模拟,后者的目标是建立沉积特征的连续谱、凝练新的科学问题。本文提出一个勘察式模拟的方法论框架,即根据控制方程确定自变量的定义域,进而由模拟计算给出应变量的值域,并结合物质收支平衡原理和“圆台状环礁”几何模型,以此方法预估环礁及其海底阶地物质输运和堆积格局。环礁是珊瑚礁的独特类型,其礁盘区提供了礁体生长和礁外坡、海底阶地堆积的几乎全部物源。结果表明,环礁自身生长受控于生物碎屑生产,而海底阶地的范围和沉积速率不仅决定于离礁悬沙通量,而且受到环礁外水深和海盆环流的制约。悬沙输运和重力流过程形成常态沉降和水下滑坡的交替沉积。此模型所预测的环礁沉积体系高程-面积曲线与南海环礁的实际曲线相对照,可获得环礁演化的机制信息。模拟结果还提示了需进一步研究的科学问题,如环礁生长规模及其控制机制、环礁沉积体系中周期性沉积的时间尺度、环礁外坡由于珊瑚生长自组织机制形成的重力流事件与地震等极端事件的对比和机制识别、环礁群的海底阶地沉积记录多样性、海面变化对环礁演化的影响和沉积记录、环礁人居环境安全等。     

荧光淬灭剂TrueBlack Lipofuscin对珊瑚自体荧光的消除及其在免疫荧光标记中的应用

自体荧光是生物体内部组织成分在吸收光时自然发出的荧光,会影响人工标记荧光的有效识别,严重干扰对抗体标记的目的蛋白荧光的观察及数据分析,在珊瑚冰冻切片免疫荧光标记研究中尤为突显。为更有效地去除珊瑚组织切片中的自体荧光,本研究以共生模式种花伞软珊瑚（Xenia sp.）为研究对象,首次尝试在花伞软珊瑚冰冻切片免疫荧光染色中,使用一种在小鼠和人体组织切片中常用的TrueBlack Lipofuscin自体荧光淬灭剂,并与已有研究中的酒精梯度脱水法进行比较。结果表明,使用荧光淬灭剂TrueBlack Lipofuscin后,花伞软珊瑚组织切片中的自体荧光强度是传统的酒精梯度脱水法的52.4%,且在Cy5通道下效果最佳。同时,通过珊瑚免疫荧光标记实验表明使用TrueBlack Lipofuscin的实验组特异性荧光信号强度为对照组的205.3%,背景荧光和自体荧光基本去除。     

C60全珊瑚海水混凝土的钢筋锈蚀行为研究

采用线性极化电阻法,测试了C60全珊瑚海水混凝土（coral aggregate seawater concrete,简称CASC）的线性极化曲线、自腐蚀电位（E_corr）和极化电阻（R_p）,研究了不同暴露时间、不同种类钢筋CASC的钢筋腐蚀行为,提出了提升岛礁CASC结构耐久性的建议措施。结果表明：随着暴露时间的延长,CASC的E_corr和R_p均逐渐降低,钢筋的耐蚀性能逐渐减弱。不同种类钢筋CASC耐蚀性能规律为：316不锈钢筋优于有机新涂层钢筋,优于普通钢筋。即使暴露0 d,CASC中普通钢筋仍会发生锈蚀,表明普通钢筋在不附加任何防腐措施的条件下不适用于岛礁CASC结构。综合分析阻锈效果和成本因素,316不锈钢筋的性价比明显低于有机新涂层钢筋,建议岛礁CASC工程优先选用有机新涂层钢筋。     

Deterioration processes affecting prehistoric rock art engravings in granite in NW Spain

Prehistoric rock art sites are endangered despite conservation efforts. The lack of scientific documentation regarding weathering agents affecting rock art and the absence of specific diagnostic protocols hinder the development of conservation strategies. The aim of this research was to investigate active deterioration processes in a granite petroglyph site located in Mougás (Galicia, NW Spain) by characterizing the granite, conducting a geotechnical study of the outcrop and describing and analysing the main weathering processes. Two main deterioration factors were identified. First, water favours block disjunction at the massif scale and causes pitting and surface erosion at the millimetre scale that affects the readability of the engravings. Second, high temperatures associated with wildfires cause mineral transformations that increase the susceptibility of the rock to weathering. Identifying deterioration factors is a first step in developing appropriate preventive conservation measures, which should aim to reduce rock contact time with water (technically affordable in the short term) and to reduce the probability of wildfire occurrence (technically more complex and possibly with longer‐term results). Copyright © 2018 John Wiley & Sons, Ltd.     

土石混合体分形几何特征与强度演化特征

针对土石混合体的结构性特点,以含石量为20%、30%、40%、50%、60%的土石混合体为研究对象,基于多重分形原理研究多重分形特征,研究分形维数与强度之间的关系。研究表明,土石混合体具有双重分形特征,不同尺度条件下具有不同分形指标,包括块石粒度、土体粒度以及平均粒度等分形维数,与含石量相关。单轴压缩试验表明,抗压强度随含石量增加呈现先增大后减小的趋势,根据单维分形特征,确定最优含石量约为40%。建立了含石量、不同分形维数指标与抗压强度之间的关系,分析了双重因素综合影响下抗压强度的变化特征,确定了含石量与分形维数之间存在最优区域。     

Source and supply of sediment to a shoreline salient in a fringing reef environment

Reef-associated landforms are coupled to the health of the reef ecosystem which produces the sediment that forms and maintains these landforms. However, this connection can make reef-fronted coastlines sensitive to the impacts of climate change, given that any decline in ecosystem health (e.g. decreasing sediment supply) or changes to physical processes (e.g. sea level rise, increasing wave energy) could drive the sediment budgets of these systems into a net erosive state. Therefore, knowledge of both the sediment sources and transport mechanisms is required to predict the sensitivity of reef-associated landforms to future climate change. Here, we examine the benthic habitat composition, sediment characteristics (composition, texture, and age), and transport mechanisms and pathways to understand the interconnections between coastal morphology and the reef system at Tantabiddi, Ningaloo Reef, Western Australia. Benthic surveys and sediment composition analysis revealed that although live coral accounts for less than 5% of the benthic cover, coral is the dominant sediment constituent (34% on average). Sediment ages (²³⁸U/²³⁰Th) were mostly found to be thousands of years old, suggesting that the primary sediment source is relic reef material (e.g. Holocene reef framework). Sediment transport across the lagoon was quantified through measurements of ripple migration rates, which were found to be shoreward migrating and responsible for feeding the large shoreline salient in the lee of the reef. The derived sediment fluxes were comparable with previously measured rates of sediment production by bioerosion. These results suggest that sediment budgets of systems dependent on old (>10³ years) source materials may be more resilient to climate change as present-day reef health and community composition (i.e. sources of ‘new’ carbonate production) have limited influence on sediment supply. Therefore, the vulnerability of reef-associated landforms in these systems will be dictated by future changes to mechanisms of sediment generation (e.g. bioerosion) and/or physical processes. © 2018 John Wiley & Sons, Ltd.     

包裹碎石桩加固的砂土液化机理试验研究

通过分别开展包裹碎石桩加固、碎石桩加固以及未加固的饱和砂土液化振动台试验,对比分析不同加固类型下的抗液化性能,重点剖析包裹碎石桩加固的砂土液化机理。试验表明:振动加载过程中,包裹碎石桩始终保持桩体的完整性与良好的排水性能且其加固模型地基的总沉降量相较于未加固模型地基减少了50%,相较于碎石桩加固模型地基减少了31.8%。包裹碎石桩加固模型排出水量较未加固模型地基提高了33.3%,较碎石桩加固模型地基提高了16.6%;包裹碎石桩加固模型地基的超静孔压值下降显著且地基下层砂土出现未液化的现象;并进一步发现包裹碎石桩的排水加固作用沿土层竖向深度呈递增趋势。因此,可以发现包裹碎石桩加固砂土液化的抗震性能优于碎石桩。     

地震减灾工程下格宾石笼拦挡坝支护技术研究

鉴于格宾石笼护岸、护坡等优质特性,对其应用至地震减灾工程进行研究。经分析可知,格宾石笼主要利用双绞合六边形金属网片组合为箱笼,再装填石料堆筑构成防护整体;格宾石笼具有高强度耐久性、透水性、整体性与柔韧性和施工过程简单便利等特征。依据格宾石笼构造与特性分析,分别将地震减灾工程下格宾石笼拦挡坝施工划分为格宾石笼护基与格宾石笼护坡两部分进行研究。利用测量放线、挖掘基础、规整地基、铺垫反滤层、格宾放置与连接、支顶加固、石料装填封盖等步骤实现格宾石笼护基施工。通过削坡、铺设土工布、砂砾垫层、安装网箱、装填石料和封盖等步骤实现格宾石笼护坡施工。分别在冲击力、位移和能量三方面验证格宾石笼拦挡坝支护技术,实验结果表明,冲击力和坝体自身材料性质有关联,格宾拦挡坝材料属于柔性材料,冲击力由此减小,耗费冲击力能量效果十分明显;坝体可以利用整个结构全部能量承担很大负载;格宾石笼拦挡坝体耗能效果显然优于浆砌石坝。     

Dynamic simulation of tropical coral reef ecosystem being disturbed by multiple situations

In consideration of the rapid degradation of coral reef ecosystems, the establishment of models is helpful to comprehend the degradation mechanism of coral reef ecosystems and predict the development process of coral reef communities. According to the characteristics of complex ecosystem of tropical coral reefs in China, the coral reef functional group is the core level variable; combined with the multiple feedback effects of coral reef functional groups and environmental changes, the study presents a coral reef ecosystem dynamics model with hermatypic corals as the core. Based on the simulation of the assumed initial value and the internal feedback of the system, the results show that in the basic simulation(relative health conditions), the coverage area of live corals and coral reefs generally decreased first and then increased, and increased by 4.67% and 6.38% between2010 and 2050, respectively. Based on the calibration model and the current situation of the studied area, the multi-factor disturbance effects of coral reef communities were simulated and explored by setting up three scenarios involving fishing policy, terrestrial deposition, and inorganic nitrogen emissions. Among them, in the single factor disturbance, the fishing policy exerts the most direct impact on the community decline; and the succession phenomenon is obvious; the terrestrial sedimentation has a faster and more integrated effect on the community decline; the effect of inorganic nitrogen emission on the community decline is relatively slow. In the double/multi-factor disturbance, the superimposed disturbance will aggravate the multi-source feedback effect of the coral reef communities development, accelerate the community decay rate, and make its development trajectory more complicated and diverse. This method provides a scientific and feasible method for simulating the damage of long-term coral reef community and exploring the development law and adaptive management of coral reef ecosystems. In the future, it can be further studied in the ecological restoration process and decisionmaking direction of coral reefs.     

Introduction to dynamics of stone arches

The dynamic analysis of stone arches, made up of rigid voussoir laid dray, can be performed in two phases. First of all the value of the horizontal acceleration necessary to turn the structure into a mechanism and the corresponding mechanism must be determined. Then the dynamic behaviour of such a mechanism under a given acceleration time history can be studied. The first step is a static matter. The second one requires the solution of the non-linear equation of motion of the one-degree-of-freedom system in which the arch is turned. In this paper an iteration procedure is proposed to find out the mechanism. Then the structural behaviour of the mechanism is analysed. Both free and forced vibrations are investigated and the study is limited to the first-half cycle of vibration. Damping is not considered and sliding between the blocks at the hinge sections is not allowed. © 1998 John Wiley & Sons, Ltd.