边界条件对多年冻土路基热稳定性的影响分析

多年冻土区的年平均气温是影响冻土路基边界条件的重要因素. 在附面层原理的基础上,考虑采用带有相变的控制方程和数值方法,以相同尺度的路基模型为前提,选取不同的年平均气温为影响因素,对青藏工程走廊公路路基的人为冻土上限和年平均地温进行了研究. 结果表明：公路路基下年平均地温随着年平均气温的升高而升高,人为冻土上限随着年平均气温的升高而显著下降. 在年平均气温为-7.16 ℃时,路基修筑50 a后其年平均地温为-3.61 ℃,其人为冻土上限为-0.97 m;年平均气温为-3.21 ℃的条件下,路基修筑50 a后其年平均地温仅为-0.1 ℃,其人为冻土上限也降至-13.11 m. 因此,可以看出：在未来气候持续变暖的背景下,现有处于稳定状态的冻土路基将逐渐变得不稳定.     

多年冻土区道路工程病害类型及特征研究

多年冻土及多年冻土区恶劣的环境给工程构筑物的建设及维护带来了极大的挑战。以青藏工程走廊内的青藏公路、青藏铁路两大道路工程为研究对象,系统论述了其路基工程、桥梁工程、涵洞工程的主要病害类型及分布特征。现场调查显示,青藏公路80%的路基病害由多年冻土融沉所引起,主要表现为严重的不均匀沉降变形和纵向裂缝,且主要发生在高填方路基上。这两种病害与多年冻土地温及含冰量密切相关,地温越高,含冰量越大,病害越为严重。青藏公路桥梁工程的病害主要集中在附属工程及上部结构上,而涵洞工程病害则主要由冻胀、融沉作用、泥石流淤积、冰塞以及施工原因导致。青藏铁路沿线现场监测及调查结果表明,目前铁路路基病害主要为高温冻土区普通路基的（不均匀）沉降变形、纵向裂缝、路桥过渡段沉降变形、风沙灾害及块碎石材料风化引起的冷却路基结构失效等。此外,青藏工程走廊内广泛分布着包括冻胀丘、冰椎、冰幔、热融湖塘等不良冻土地质现象,当上述不良地质现象与工程接近时,会对道路工程的稳定性造成威胁,严重时可导致一些工程病害的发生。     

青藏工程走廊楚玛尔河高平原区路基边界温度特征

基于青藏高原楚玛尔河地区青藏公路里程K2968+200断面浅层地温监测数据（地表下5 cm）,拟合了边界温度的回归方程,分析了公路路基及铁路路基两侧表层温度的特征.同时对路基坡面温度和理论辐射值的相关性进行了分析.结果表明：边界温度回归方程拟合程度较高,可作为冻土路基数值模拟温度边界选取的参考依据;监测断面公路和铁路路基都表现出显著的阴阳坡差异,公路左右坡面冬季温度差异达11.49℃,年均值差4.77℃,冬季铁路路基左右坡脚温度差异达到5.34℃,年均值差3.33℃,天然地表与气温的差值为5.2℃;根据融化与冻结n系数,位于阳坡一侧的冻结n系数较低且融化n系数大,表现为吸热;阴坡一侧冻结n系数较大,整体呈现出放热效应;路基边坡太阳理论辐射与温度变化趋势基本一致.     

New spatial dimensions of global cityscapes: From reviewing existing concepts to a conceptual spatial approach

Current global urbanisation processes are leading to new forms of massive urban constellations. The conceptualisations and classifications of these, however, are often ambiguous, overlap or lag behind in scientific literature. This article examines whether there is a common denominator to define and delimitate–and ultimately map–these new dimensions of cityscapes. In an extensive literature review we analysed and juxtaposed some of the most common concepts such as megacity, megaregion or megalopolis. We observed that many concepts are abstract or unspecific, and for those concepts for which physical parameters exist, the parameters are neither properly defined nor used in standardised ways. While understandably concepts originate from various disciplines, the authors identify a need for more precise definition and use of parameters. We conclude that often, spatial patterns of large urban areas resemble each other considerably but the definitions vary so widely that these differences may surpass any inconsistencies in the spatial delimitation process. In other words, today we have tools such as earth observation data and Geographic Information Systems to parameterise if clear definitions are provided. This appears not to be the case. The limiting factor when delineating large urban areas seems to be a commonly agreed ontology.     

1: Subduction, slab detachment and mineralization: The Neogene in the Apuseni Mountains and Carpathians

The Inner Carpathians comprise several distinct Neogene late-stage orogenic Pb–Zn–Cu–Ag–Au ore districts. The mineral deposits in these districts are closely related to volcanic and subvolcanic rocks, and represent mainly porphyry and epithermal vein deposits, which formed within short periods of time in each district. Here, we discuss possible geodynamic and structural controls that suggest why some of the Neogene volcanic districts within the Carpathians comprise abundant mineralization, while others are barren. The Neogene period has been characterized by an overall geodynamic regime of subduction, where primary roll-back of the subducted slab and secondary phenomena, like slab break-off and the development of slab windows, could have contributed to the evolution, location and type of volcanic activity. Structural features developing in the overlying lithosphere and visible in the Carpathian crust, such as transtensional wrench corridors, block rotation and relay structures due to extrusion tectonics, have probably acted in focusing hydrothermal activity. As a result of particular events in the geodynamic evolution and the development of specific structural features, mineralization formed during fluid channelling within transtensional wrench settings and during periods of extension related to block rotation.In the Slovakian ore district of the Western Carpathians, Neogene volcanism and associated mineralization were localized by sinistral, NE-trending wrench corridors, which formed part of the extruding Alcapa block. The Baia Mare ore district, in the Eastern Carpathians, reflects a transtensional wrench setting on distributed oversteps close to the termination of the Dragos Voda fault. There, mineralization was spatially controlled by the transtensional Dragos Voda master fault and associated cross-fault systems. The Golden Quadrangle Cu–Au ore district of the Southern Apuseni Mountains reflects an unusual rotated transtensional/extensional setting close to the termination of a graben system. There, fluid flow was probably localized by fault propagation at the inner tip of the graben system.The spatial and temporal evolution of the magmatism and its changing geochemical signature from (N)W to (S)E strongly suggests a link with the contemporaneous northeastward roll-back of the subducted slab and a progressive southeastward detachment during accelerating roll-back. This geodynamic evolution is further supported by the present-day overall and detailed mantle lithospheric density images, the present-day heat flow patterns, the crustal architecture and its interpreted evolution, and the spatial and temporal evolution of depocentres around the Carpathian arc. In contrast to all these features, the mineral deposits in the West Carpathians, East Carpathians and Apuseni Mountains are too synchronous with respect to their individual volcanic history and contrast too much with younger volcanics of similar style, but barren, in southeastern parts of the Carpathians to simply link them directly to the slab evolution. In all three districts, the presence of magmatic fluids released from shallow plutons and their mixing with meteoric water were critical for mineralization, requiring transtensional or extensional local regimes at the time of mineralization, possibly following initial compressional regimes.These three systems show that mineralization was probably controlled by the superposition of favourable mantle lithospheric conditions and partly independent, evolving upper crustal deformation conditions.In the 13 to 11 Ma period the dominant mineralization formed all across the Carpathians, and was superimposed on structurally favourable crustal areas with, at that time, volcanic–hydrothermal activity. The period may reflect the moment when the (upper part of the) crust failed under lithospheric extension imposed by the slab evolution. This crustal failure would have fragmented the overriding plate, possibly breaking up the thermal lid, to provoke intensive fluid flow in specific areas, and allowed subsequent accelerated tectonic development, block rotation and extrusion of a “family of sub-blocks” that are arbitrarily regarded as the Tisia–Dacia or Alcapa blocks, even though they have lost their internal entity.     

雄安新区生态安全格局识别与优化策略

雄安新区的设立对于调整、优化京津冀城市空间结构具有深远的历史意义。面向“生态标杆”的新区建设理念,生态安全格局识别及优化是保障雄安新区生态安全、实现可持续发展的基本空间途径。本文基于雄县、容城、安新三县生态本底特征,选取并定量评估粮食供给、产水、土壤保持、生境维持和近水游憩5种生态系统服务,识别生态源地;利用VIIRS/DNB夜间灯光数据修正基于地类赋值的基本阻力面,并运用最小累积阻力模型识别生态廊道;最后基于现状生态安全格局,探讨绿色生态宜居新城目标下的生态安全格局优化策略。研究结果表明：雄安三县生态源地占到全区土地总面积的41.88%,包含14个生态源地斑块,主要分布在白洋淀周边;生态廊道总长度107.21 km,分4大组团呈环状分布;现有生态源地辐射面积占到全区的70.6%,在雄县县城周边新建辐射面积为227 km²的生态源地可满足全区85%的源地辐射面积规模要求。本文提出的生态安全格局优化方案可为雄安新区开发建设提供空间指引。     

文化廊道空间界定之CCSPM模型构建——以滇西南跨境文化廊道为例

基于景观信息链理论,按照识别文化基因、确定文化点、模拟廊道空间的过程,结合阻力模型及原理,运用ArcGIS 工具从文化点对廊道文化的传播重要性、文化点的区域影响力、各文化点的空间关系以及自然环境对文化传播的约束等4个方面,构建出CCSPM（cultural corridor spatial pattern model）模型,并运用该方法界定滇西南跨境文化廊道的空间范围。结果显示：① 滇西南跨境文化廊道的文化元素影响范围沿交通线集聚但空间差异性较大;② 滇西南跨境文化廊道总体格局、分布趋势和历史进程大致相符,模型能较有效地表征文化廊道空间范围。该方法为文化廊道空间研究提供新的研究思路,进而为分析廊道内部的文化连接方向和程度及文化遗产的整体保护与开发提供空间信息支持。     

吉林省东部山区隧道洞室开挖涌水量估算分析

隧道洞身在中等风化岩层中,水文地质条件相对比较复杂。隧道施工时需要进行人工降水,以满足施工条件,为此估算隧道洞体涌水量在设计时显得极为重要。本文以凉水隧道工程为例,应用泉水流量汇总法、地下水径流模数法和水平廊道法对隧道涌水量计算并进行对比分析,验证三种方法的合理性和有效性,为设计和施工降水提供一定的参考依据。     

Thermal-mechanical Influences and Environmental Effects of Expressway Construction on the Qinghai-Tibet Permafrost Engineering Corridor

The Qinghai-Tibet Engineering Corridor (QTEC) is a strategic passage between Tibet and central China. In the past half century, several major projects have been built in this narrow corridor with vulnerable geoenvironment. Along with a new round of economic development of the Tibet autonomous region, some major linear projects including expressway, double-tracking railway, high voltage power transmission line have been incorporated into the national development planning within the corridor, and especially the expressway construction is imminent now. In the QTEC, permafrost is a controlling factor of geological environment, which will impose great restrictions on engineering construction. In turn, engineering construction will induce significant effects on permafrost geological environment. With more and more linear infrastructures crowding into the QTEC, the thermal interaction among permafrost engineering and engineering disturbance on permafrost thermal-mechanical regime will be more significant. With respect to this issue, a research program focusing on thermal-mechanical influences and environmental effects of expressway construction on the Qinghai-Tibet permafrost engineering corridor was started and supported by the National Natural Science Foundation of China. In this paper, the research significance, key scientific issues, main research contents and goals of the program are introduced so as to provide some references for related researchers and engineers.     

中新经济走廊地质矿产特征及找矿潜力

中新经济走廊纵贯东南亚中南半岛,地处全球著名的特提斯成矿域,矿产资源丰富,但资源勘查开发水平滞后,成为中国"一带一路"战略实施的优选地区之一。该区一大批矿床的发现和一系列新矿山的陆续建成投产,必将为区域经济发展和社会进步注入新的活力。通过对中新经济走廊的大型或代表性矿床的地质特征和成矿背景的总结,并对研究区主要矿床的成矿作用、成矿模式及找矿潜力进行讨论,旨在提高对中新经济走廊矿产资源重要性的认识水平,进而为实施"一带一路"战略在东南亚地区的工作部署提供科学依据。