Theory of one dimensional consolidation of two-layered soil with partially drained boundaries

In this paper, a fully explicit analytical solution is presented for one-dimensional consolidation of two-layered soils with partially drained boundaries. It can be shown that the available analytical solutions so far developed for one dimensional consolidation of soil are the special cases of the solution presented herein. According to the solution, some diagrams are prepared and the relevant consolidation behavior of layered soils associated with partially drained boundaries is discussed in detail. Furthermore, the applications of the solution are illustrated in an example problem.     

Formation Mechanism of "Drag Depressions" and Irregular Boundaries in Intraplate Deformation

Almost all intraplate caprocks experienced strong deformation during the convergence of microplates, and then disintegrated into many secondary geologic units with the special characters, such as irregular boundaries and particular structural assemblages. In order to understand the formation mechanism of these special phenomena, a rheological experiment on the structural scenery of the Tongling area is carried out. The result shows that the primary regular and uniform boundaries of the Tongling area becomes irregular because of the enclosing and confinement of surrounding geological units in the process of "compression-shearing-rotation-drag"; simultaneously, two specific "drag depressions" developed at two opposite corners of the block. The former and the later phenomena can be regarded as a typical regional-scale rheological effect and necessary outcome of intraplate deformation respectively.     

昆明吴家营岩溶水系统边界的水文地球化学分析

西南岩溶水系统边界条件复杂,其中水头隔水边界在水动力条件改变的情况下具有不稳定的隔水特性。文章以昆明吴家营岩溶地下水系统为例,通过水化学组分动态序列图解法、数理统计法及水文地球化学模拟等方法对研究区边界特性进行了研究。研究结果表明该岩溶水系统水动力条件丰水季优于枯水季,并存在与边界外发生水力联系的越流通道;丰水季时岩溶槽谷区地下水在高水力梯度的驱动下向下绕过玄武岩隔水层,通过下部阳新灰岩对系统内岩溶水进行越流补给,枯水季受深部滞流阻水影响,越流补给现象不明显;由此得出此类水头边界的隔水特性会随水动力条件的改变而具有动态响应特征。研究成果对当地岩溶水资源量的评价和合理开发利用提供科学依据。      

Political Organization of Space in Advanced Placement Human Geography

Abstract

The political geography section of the course offers the opportunity to introduce students to one of the most important ways in which humans have divided up the surface of the Earth for purposes of management and control. By challenging students to consider what lies behind the patterns on political maps, this segment of the course can encourage the development of a critical geographical perspective while enhancing student appreciation of the link between geography and current events.     

Morphodynamic research challenges for braided river environments: Lessons from the iconic case of New Zealand

Pressures on braided river systems in New Zealand are increasing due to anthropogenic stresses such as demand for irrigation water, braidplain conversion to farmland and invasive vegetation, as well as extreme natural events associated with earthquakes and climate change. These pressures create issues around preserving braided river physical environments and associated ecosystems, and managing hazards such as floods, aggradation and erosion. A need for more robust understanding and quantification of braided river morphodynamic processes underpins many of these issues. Here, we present eight morphodynamic research challenges to service this need. The first four research challenges relate to managing aggradation-related flooding hazards; the last four address issues stem largely from recent dairy expansion, which has created huge pressure to take land and irrigation water from the alp-fed braided rivers and to alter flow regimes at their mouths. Hāpua, the freshwater lagoons found where most braided rivers meet the coast, show complex morphodynamic behaviour in response to the interplay of river and coastal processes, and their special ecosystems are sensitive to river flow and sediment load changes. We discuss how physical laboratory experiments and novel numerical modelling can help to understand the morphological processes braided rivers undergo, and we show how those research advances could inform planning and legal decisions to regulate land rights and irrigation water allocation on New Zealand's braidplains. We illustrate these environmental and engineering issues and research challenges with examples from the Kowhai, Waiho, Waiau, Rangitata and Hurunui Rivers. © 2020 John Wiley & Sons, Ltd.     

Recent geodynamic evolution of convergent plate margins and the reconstruction of fossil plate boundaries

Summary The discovery of paleoplates buried in the upper mantle leads to an interpretation of the subduction as a discontinuous process running in cycles and shifting the place of its operation in or against the direction of ocean floor spreading. This mechanism explains the distribution of calc-alkaline volcanism of different age in fossil convergent plate boundaries. The establishment of regular spatial correlation of the aseismic gap in the Wadati-Benioff zones with the distribution of calc-alkaline volcanism enables to reconstruct fossil plate boundaries and to define allochtonous terranes in apparently homogeneous continental plates. The hampering effect of the ocean floor morphology and of the fragments of continental plates approaching the trench, which substantially influences the rates of subduction and the geodynamic history of active continental margins in different domains along the trench, allows us to understand the complicated geological development of continental wedges in fossil convergent plate margins. The establishment of the segmented nature of active subduction zones and the dramatic morphology of the lower limit of the active subducted slab along the trench help us to interpret extensive lateral gaps in volcanic chains overlying active as well as fossil subduction zones.     

辅助边界谈判划界子系统设计及关键技术

边界谈判划界是一个重要而又复杂的问题,本文结合谈判划界业务流程,探讨了在GIS空间技术支持下,谈判划界系统各功能模块设计以及系统的数据设计,实现对谈判划界数据的有效管理,提供划界辅助工具和资源评价分析工具,为谈判划界提供决策支持.     

北祁连-河西地区强震地点预测

借助弹性块体边界负位错模型,获取了北祁连 河西地区1971～2000年5个时段地壳垂直运动反映的 构造块体及其边界断层运动、变形参量及构造梯度场的时空演化图像,高应变能积累部位和锁定能量强度。研究 了与门源Ms6.4、景泰Ms6.2、永登Ms5.8、景泰Ms5.9、玉门Ms5.9以及2003年10月25日民乐 山丹Ms6.1等 强震孕育有关的背景性前兆特征,初步建立了该区强震地点判定的定量依据:①在较大范围强烈隆起区内及其边 缘、梯度场高值区内及其边缘,尤其是与构造走向较为一致、隆起量5mm/a以上或梯度值8×10-8/a以上能达到 方圆50～100km甚至更大的区域;②强位错(3mm/a以上)锁定区段及其附近,较强负位错应力降或负位错地震 矩(分别为5×103Pa/a和5×1016Nm/a左右甚至更高)区段及其附近;或者显著加强段及其附近,可能发生6级左 右或6级以上地震。对应的异常越突出、项数越多、位置越重合,发震危险性越大。     

川滇菱形块体东边界地震精定位

选用四川及云南地震台站资料,采用多阶段地震定位法(Hypo2000+Velest+HypoDD),对四川境内川滇菱形块体东边界的道孚南至巧家段2010年1月1日~2014年12月31日7787次地震进行了精定位。精定位后,震源位置精度明显提高,震中分布与地震断裂带线性展布较一致。定位结果显示,鲜水河断裂带东南段地震分布相对密集,鲜水河南段与安宁河断裂带、小金河断裂带及以东的大凉山断裂带交叉区域相对密集。深度剖面图沿活动断裂带地震活动分段活动特征明显,横跨鲜水河、安宁河和大凉山等断裂的剖面呈现出石棉附近多断裂交汇处的断层间复杂的相互作用,地震明显分为深、浅两丛。15~20km深度范围地震非常稀少,这与朱艾斓提出的14~19km塑性流变的层厚和位置较一致。     

地球界限概念框架及其研究进展

“地球界限(Planetary Boundaries)”是指用于界定“安全运行空间(safe operating space)”的边界值,是Johan Rockstr?m等近年来提出的旨在保障人类生存和发展的重要概念框架。该框架一经提出就引起了广泛关注,一方面质疑者对这一概念框架的科学意义以及评估方法提出批评;另一方面支持者则对其评估方法、研究内容和研究尺度进行了完善和扩展,并取得了重要的成果。为了促进国内学者对该领域的了解和应用,论文在回顾相关文献的基础上,首先介绍了“地球界限”的概念内涵,并将其与中国学者所熟知的环境承载力等概念进行了比较分析;随后总结了该概念框架的争议观点,同时也对其近期的发展状况进行了评述;最后结合中国目前的发展状况,分析了“地球界限”概念框架对中国可持续发展的借鉴意义,并对未来的研究提出了展望,包括① 进一步了解不同地球系统过程的相互作用机制,完善“地球界限”的指标评估体系;② 明确“地球界限”与生态系统服务以及人类福祉三者之间的内在联系;③ 结合“地球界限”的评估结果,加强变革式环境治理的研究。