坡顶住宅开裂原因探讨     

刘东  匡立新 《化工矿产地质》2004,26(2):117-121

由于边坡挡土墙设计失误、基础施工影响及原事故处理不当等原因,造成施工地段桩基-地基土-挡土墙体系超量位移,从而导致桌坡顶住宅楼开裂。通过在相应部位施工钻孔灌注桩,完善相关排水、隔水系统等措施,使住宅和边坡达到稳定。由此,应引起工程界对坡顶建筑-基础-地基土-边坡支护体系相互作用机理相关问题的重视。  相似文献   

多普勒雷达径向速度资料在对流天气预报中的应用   总被引：4，自引：7，他引：4  

王丽荣  胡志群  汤达章  赵瑞金  匡顺四 《气象科学》2007,27(6):695-701

本文探讨了降水前多普勒天气雷达径向速度资料在对流性天气预报中的应用方法:图像定性分析法及EVAD技术定量分析法。并以2004年5日15时出现在石家庄的对流天气为例,详细介绍了利用这两种方法预报对流天气的步骤。通过对2004年10个对流性天气过程及其对应的径向速度资料的仔细分析,总结出几个定量的利用径向速度资料预报对流天气的指标,对流出现之前:(1)摩擦层开始出现辐合现象,辐合超前对流出现时间平均为8.2 h;(2)1.5°仰角径向速度图像上25 km范围内均出现了距离折叠现象;(3)25 km以内的低层50%出现了E或NE风,其他50%为S到SE风。另外,反查2004年5—6月径向速度资料发现:低层辐合和距离折叠均出现的日期,当天出现对流性降水的几率为77.3%。这些指标对预测预报石家庄地区对流性天气发生发展有一定指示作用,对其它地区也有一定的推广价值。  相似文献   

Intensifying aeolian activity following the end-Permian mass extinction: Evidence from the Late Permian–Early Triassic terrestrial sedimentary record of the Ordos Basin,North China     

Zhicai Zhu  Hongwei Kuang  Yongqing Liu  Michael J. Benton  Andrew J. Newell  Huan Xu  Wei An  Shu'an Ji  Shichao Xu  Nan Peng  Qingguo Zhai 《Sedimentology》2020,67(5):2691-2720

Sedimentary successions provide direct evidence of climate and tectonics, and these give clues about the causes of the mass extinction around the Permian–Triassic boundary. Terrestrial Permian–Triassic boundary strata in the eastern Ordos Basin, North China, include the Late Permian Sunjiagou, Early Triassic Liujiagou and late Early Triassic Heshanggou formations in ascending order. The Sunjiagou Formation comprises cross-bedded sandstones overlaid by mudstones, indicating meandering rivers with channel, point bar and floodplain deposits. The Liujiagou Formation was formed in braided rivers of arid sand bars interacting with some aeolian dune deposits, distinguished by abundant sandstones where diverse trough and planar cross-bedding and aeolian structures (for example, inverse climbing-ripple, translatent-ripple lamination, grainfall and grainflow laminations) interchange vertically and laterally. The Heshanggou Formation is a rhythmic succession of mudstones interbedded with thin medium-grained sandstones mainly deposited in a shallow lacustrine environment. Overall, the sharp meandering to braided to shallow lake sedimentary transition documents palaeoenvironmental changes from semi-arid to arid and then to semi-humid conditions across the Permian–Triassic boundary. The die-off of tetrapods and plants, decreased bioturbation levels in the uppermost Sunjiagou Formation, and the bloom of microbially-induced sedimentary structures in the Liujiagou Formation marks the mass extinction around the Permian–Triassic boundary. The disappearance of microbially-induced sedimentary structures, increasingly intense bioturbation from bottom to top and the reoccurrence of reptile footprints in the Heshanggou Formation reveal gradual recovery of the ecosystem after the Permian–Triassic boundary extinction. This study is the first to identify the intensification of aeolian activity following the end-Permian mass extinction in North China. Moreover, while northern North China continued to be uplifted tectonically from the Late Palaeozoic to Late Mesozoic, the switch of sedimentary patterns across the Permian–Triassic boundary in Shanxi is largely linked to the development of an arid and subsequently semi-humid climate condition, which probably directly affected the collapse and delayed recovery in palaeoecosystems.  相似文献   

沉水植物苦草根系功能性状对基质类型和种植密度的响应及其与个体表现关系     

陈俊格  陈矿  王和云  易春龙  高健  文冬华  张润龙 《湖泊科学》2024,36(1):247-260

根系功能性状体现了植物细根的生长状况及其对外部环境的适应性,然而根系功能性状响应环境变化的时间稳定性如何仍不清楚。苦草(Vallisneria natans)是水体沉水植被修复的先锋种类,细根在其种群重建初期起着重要作用。该研究设计了草垫、草垫+沙子、草垫+黄泥及草垫+底泥4种生长基质和100株/m²以及200株/m²两种种植密度并将其两两组合,以模拟自然生境不同的基质和密度情况,并在不同时期对苦草功能性状指标进行取样测定,通过重复测量二元方差分析研究基质和密度对根系功能指标的影响,并通过线性拟合模型探讨个体水平的生长表现(生物量分配、营养吸收、个体定植)与具体的根系功能性状之间的关系对环境变化的响应。结果表明:所有测量指标均受到基质条件的显著影响,部分根系功能性状指标如根冠比(RSR)、根干重、比根长(SRL)、根比表面积(SRA)、根组织密度(RTD)、根系锚定力和根体积受密度的影响显著。苦草生物量的分配主要受基质条件的影响,对营养的吸收、运输及根系固着能力受基质和密度的共同影响。线性拟合模型表明SRA、RTD、根直径、根表面积以及根体积在个体水平上能一定程度地预测RSR对环境变化的响应,且RTD的预测效果最好;根冠比、SRA、生根数、总根长、根表面积以及根体积在个体水平上能一定程度地预测SRL对环境变化的响应,其中生根数的预测效果最好;SRA、根直径、根表面积以及根体积在个体水平上能一定程度地预测根系锚定力对环境变化的响应,并且SRA的预测效果最好。但是基质和密度在不同时期对苦草根系功能性状的影响方向会发生改变,当用根系功能性状预测植物个体表现时,需要考虑种群重建所处的时期。  相似文献   

大别造山带南坡晚白垩世玄武岩源区地幔特征   总被引：9，自引：1，他引：9  

匡少平  张本仁  凌文黎  韩吟文 《地质科学》2001,36(2):203-211

大别造山带南坡中生代断陷盆地中出露大量晚白垩世碱性玄武岩类。因岩浆受结晶分异和陆壳混染影响微弱,其成分基本可代表本区原生玄武岩浆。在微量元素原始地幔标准化蛛网图上,本区玄武岩具有地壳富集组分Pb、K、Rb、Ba等的正异常和Nb、P、Hf等高场强元素的负异常。同位素和微量元素特征显示,玄武岩浆来自亏损地幔(DM)和富集地幔(EM+EM)混合源区。玄武岩源区地幔中Pb的富集和Nb、P、Hf等的亏损基本可由中国东部亏损地幔与榴辉岩的混合获得,由此揭示富集地幔端元组成特征可能与晚白垩世前造山带根部榴辉岩拆沉并参与地幔再循环有关。  相似文献   

Timing and mechanism of reservoir forming in the Upper Triassic Halahatang Formation,Yuqi block,Tarim Basin,northwestern China     

Lixiong Kuang  Hao Zheng  Mingyan Wang  Taizhu Huang  Chensheng Liu 《Marine and Petroleum Geology》2010

The Yuqi block is an important area for oil and gas exploration in the northern Akekule uplift, Tarim Basin, northwestern China. The Upper Triassic Halahatang Formation (T₃h) within the Yuqi block can be subdivided into a lowstand system tract (LST), a transgressive system tract (TST), and a highstand system tract (HST), based on a study of initial and maximum flood surfaces. Oil in the lowstand system tract of the Halahatang Formation is characterized by medium to lightweight (0.8075 g/cm³–0.9258 g/cm³), low sulfur content (0.41%–1.4%), and high paraffin content (9.65%–10.25%). The distribution of oil and gas is principally controlled by low-amplitude anticlines and faults. Based on studies of fluorescence thin sections and homogenization temperatures of fluid inclusions, reservoirs in the T₃h were formed in at least two stages of hydrocarbon charge and accumulation. During the first stage (Jurassic–Cretaceous) both the structural traps and hydrocarbon reservoirs were initiated; during the second stage (Cenozoic) the structural traps were finally formed and the reservoirs were structurally modified. The reservoir-forming mechanism involved external hydrocarbon sources (i.e. younger reservoirs with oil and gas sourced from old rocks), two directions (vertical and lateral) of expulsion, and multi-stage accumulation. This model provides a theoretical fundament for future oil and gas exploration in the Tarim Basin and other similar basins in northwestern China.  相似文献   

Research progress and prospects of digital restructuring of global-local interactions北大核心CSCD     

Kuang A.  Wang M.  Zhang Y. 《地理科学进展》2023,(2):380-391

Global-local interaction is an important research topic in economic geography. In recent years, the rapid development of digitalization in various countries and regions has profoundly affected the global production and trade networks. However, there is a lack of systematic theoretical discussion on digitalization and global-local interaction studies. The objective of this study is to conceptually rethink the role of digitalization in reshaping global-local interactions from a dynamic and relational perspective. To do this, the study first systematically reviewed the digital turn in economic geography and discussed the rethinking of digitalization. It is found that the understanding of digitalization is gradually moving beyond the limits of isolated, static, and passive technocentric approaches and towards a more dynamic, relational, and open perspective. Second, the study combined the "digital turn" with the "relational turn" in relational economic geography, which constructs theoretical bridges between digitalization and global-local studies. Third, this study provided a basic understanding for sorting out the evolution of the research frameworks, that is, from the global value chain (GVC) to the global production network (GPN) and then to the digital ecosystem (DE). We argued that digitalization has been deeply involved in shaping the global economic landscape, restructuring global-local production relations, and reconstructing regional development. Based on this recognition, we discussed the primary performance of digitalization on the restructuring of global-local interaction from three aspects: enterprise relationship, spatial effect and interaction mechanism. Finally, grounded in the practice of China's urban and regional digital economy development, the possible theoretical innovations and prospects for future research on digitalization and global-local interaction in the Chinese context were proposed. The study pointed out that we can integrate the regional practices of China's digital development with more in-depth research from the perspectives of the platform ecosystems, spatial effects, location analysis, local development models, and so on in future research. © 2023, Editorial office of PROGRESS IN GEOGRAPHY. All rights reserved.  相似文献   

1986—2021年国家自然科学基金资助大气科学研究35年     

匡钰  王卓妮 《气象科学进展》2022,(1)

中国基础科学全面发展的一个重要标志,是1986年国家自然科学基金委员会的建立。从该年开始,基金委地学部开始资助大气科学基础研究项目。截至2021年,35年来,基金委以研究项目的遴选、资助和评估等过程为推动,不仅促成了我国大气科学研究的持续进步,更形成了一支核心研究机构和队伍。自然科学基金大气科学类项目立项呈现持续增加态势立项数量的增加出现两个快速增加的台阶:一是2000年开始。  相似文献