基于GIS的青神县暴雨洪涝灾害风险区划

随着全球变暖,气候发生变化,青神县极端天气事件频发,气象灾害特别是暴雨洪涝的发生频率有增加的趋势,给国民经济和社会发展造成重大的损失。本文主要根据气象与气候学、农业气象学、自然地理学、灾害学、自然灾害风险管理等基本理论,在GIS技术的支持下,采用风险指数法、加权综合法、自然断点等方法,绘制青神县暴雨洪涝灾害风险区划图,对青神县暴雨洪涝灾害风险进行分析和评估。结果表明,青神县高风险区和次高风险区主要分布在罗波乡、汉阳镇,以及沿江河流域,其余大部为中等及以下风险区。     

多边形统计数据空间分析的不确定性研究——以北京市海淀区人口普查数据为例

普查数据是地理学空间分析的重要数据源。由于受到数据与计算机处理能力的限制,以往的研究对普查数据空间分析的不确定性未给予足够重视,也未形成成熟的研究方法。在建筑物单元的人口普查数据支持下,本文基于多边形统计数据的可塑面积单元问题(Modifiable areal unit problem,MAUP)特征,设计了一种该类数据空间分析不确定性的研究方法,采用不同的尺度(Scale)及分区(Zoning)系统对多边形的统计数据空间分析的准确性进行了分析。实验引入尺度与形态指数,利用可视化分析和数据拟合的研究方法,对尺度及分区对空间分析结果的影响模式进行了模拟。研究结果表明:(1)以统计小区的空间分析,其结果受统计小区空间形态的影响较大,不确定性强,不能充分反映统计数据本身的空间特征;(2)规则格网能较好地保持原始统计数据的空间分布特征,但仍然受尺度及分区影响;(3)规则格网的空间分析结果及其准确性与尺度有较好的拟合关系,不同尺度下的分析结果不确定性是原始数据不同尺度特征的体现;(4)分区效应受空间分析方法的计算尺度影响,两者共同对空间分析结果产生影响。对于固定尺度的规则格网,其邻接多边形数目是分析结果不确定的主要原因。本文研究结果表明,在多边形统计数据空间分析时,应该对其使用规则格网重新聚合,并根据实际应用的需求选择多尺度分析方法,以达到实际应用目的。     

地下爆炸各向同性源和补偿线性矢量偶极源共同作用对Rg波低谷点的影响

本文利用地震面波激发理论计算了两种震源不同相对强度、相对埋深及源时间函数情况下的Rg波频谱,研究地下爆炸中各向同性(ISO)源和补偿线性矢量偶极(CLVD)源共同激发的Rg波信号低谷点特性.结果表明,由于两种震源相对强度、相对埋深及源频谱的影响,混合信号低谷点频率与单一CLVD源激发的信号有很大差异,因此实际地下爆炸中...     

塔里木盆地塔中志留系柯坪塔格组物源示踪:碎屑锆石U-Pb年代学证据

目前对塔中志留系物源的认识仍存在不确定性.利用LA-ICP-MS分析技术对塔里木盆地塔中地区志留系柯坪塔格组2件样品开展碎屑锆石U-Pb年代学研究.结果表明塔中志留系碎屑锆石主要为岩浆结晶成因,锆石年龄主要分布在早古生代460～490 Ma、新元古代760～1000 Ma、古元古代1600～2200 Ma及新太古代晚期...     

Tonian Tectonic‐Strata Regions and their Geological Significance in China

The continent of China developed through the coalescence of three major cratons(North China, Tarim and Yangtze) and continental micro-blocks through the processes of oceanic crust disappearance and acceretionary-collision of continental crusts. The strata of the Chinese continental landmass are subdivided into 12 tectonic-strata regions. Based on the composition of geological features among the three main cratons, continental micro-blocks and other major global cratons, their affinities can be p...     

自由段先注浆对预应力锚索抗拔试验结果影响研究

为了解决无法采用已注浆锚索进行抗拔试验问题,基于界面脱黏剪切模型,利用荷载传递和弹性变形理论,考虑锚索锚固段与自由段长度比L_b/L_a的影响,建立了采用自由段已注浆锚索抗拔试验结果评价锚索抗拔性能的方法。结果表明:自由段注浆对锚索抗拔力有较大幅度的提高,尤其是当界面剪切阶段由弹性向脱黏过渡时,提高比例快速增加,并在脱黏后逐渐趋于稳定。其次,锚索自由段与锚固段交界面处剪切位移和轴力最大,并向两端逐渐降低。随着拉拔力的提高,界面剪切位移和轴力都不断增大,同时向锚索两端的衰减速度也加快。此外,弹性阶段时剪应力曲线为山峰型,而脱黏阶段为马鞍型,并随抗拔力的提高,马鞍开口逐渐扩大。最后,锚固段与自由段长度比L_b/L_a对锚索极限抗拔力的影响较小,其极限抗拔力折减系数γ_Q取值介于0.81～0.83之间,且L_b/L_a=2.5时,γ_Q计算值仅比实测结果小6.02%,验证了本文方法的可行性。     

Chemical weathering and CO2 consumption in the glaciated Karuxung River catchment,Tibetan Plateau

Climate factors play critical roles in controlling chemical weathering, while chemically weathered surface material can regulate climate change. To estimate global chemical weathering fluxes and CO₂ balance, it is important to identify the characteristics and driving factors of chemical weathering and CO₂ consumption on the Tibetan Plateau, especially in glaciated catchments. The analysis of the hydro-geochemical data indicated that silicate weathering in this area was inhibited by low temperatures, while carbonate weathering was promoted by the abundant clastic rocks with fresh surfaces produced by glacial action. Carbonate weathering dominated the riverine solute generation (with a contribution of 58%, 51%, and 43% at the QiangYong Glacier (QYG), the WengGuo Hydrological Station (WGHS), and the lake estuary (LE), respectively). The oxidation of pyrite contributed to 35%, 42%, and 30% of the riverine solutes, while silicate weathering contributed to 5%, 6%, and 26% of the riverine solutes at the QYG, WGHS, and LE, respectively. The alluvial deposit of easily weathering fine silicate minerals, the higher air temperature, plant density, and soil thickness at the downstream LE in comparison to upstream and midstream may lead to longer contact time between pore water and mineral materials, thus enhancing the silicate weathering. Because of the involvement of sulfuric acid produced by the oxidation of pyrite, carbonate weathering in the upstream and midstream did not consume atmospheric CO₂, resulting in the high rate of carbonate weathering (73.9 and 75.6 t km⁻² yr⁻¹, respectively, in maximum) and potential net release of CO₂ (with an upper constraint of 35.6 and 35.2 t km⁻² yr⁻¹, respectively) at the QYG and WGHS. The above results indicate the potential of the glaciated area of the Tibetan Plateau with pyrite deposits being a substantial natural carbon source, which deserves further investigation.     

Three dimensional numerical simulation of residential building on shrink–swell soils in response to climatic conditions

Shrink–swell soils can cause distresses in buildings, and every year, the economic loss associated with this problem is huge. This paper presents a comprehensive system for simulating the soil–foundation–building system and its response to daily weather conditions. Weather data include rainfall, solar radiation, air temperature, relative humidity, and wind speed, all of which are readily available from a local weather station or the Internet. These data are used to determine simulation flux boundary conditions. Different methods are proposed to simulate different boundary conditions: bare soil, trees, and vegetation. A coupled hydro‐mechanical stress analysis is used to simulate the volume change of shrink–swell soils due to both mechanical stress and water content variations. Coupled hydro‐mechanical stress‐jointed elements are used to simulate the interaction between the soil and the slab, and general shell elements are used to simulate structural behavior. All the models are combined into one finite element program to predict the entire system's behavior. This paper first described the theory for the simulations. A site in Arlington, Texas, is then selected to demonstrate the application of the proposed system. Simulation results are shown, and a comparison between measured and predicted movements for four footings in Arlington, Texas, over a 2‐year period is presented. Finally, a three‐dimensional simulation is made for a virtual residential building on shrink–swell soils to identify the influence of various factors. Copyright © 2015 John Wiley & Sons, Ltd.     

Landform‐oriented flow‐routing algorithm for the dual‐structure loess terrain based on digital elevation models

The loess landform in the Loess Plateau of China is with typical dual structure, namely, the upper smooth positive terrain and the lower cliffy negative terrain (P–N terrain for short). Obvious differences in their morphological feature, geomorphological mechanism, and hydrological process could be found in the both areas. Based on the differences, a flow‐routing algorithm that separately addresses the dual‐structure terrain would be necessary to encompass this spatial variation in their hydrological behaviour. This paper proposes a mixed flow‐routing algorithm to address aforementioned problems. First, the loess landform surface is divided into P–N terrains based on digital elevation models. Then, specific catchment area is calculated with the new algorithm to simulate the water flows in both positive and negative terrain areas. The mixed algorithm consists of the multiple flow‐routing algorithm (multiple‐flow direction) for positive areas and the D8 algorithm for negative areas, respectively. The approach is validated in two typical geomorphologic areas with low hills and dense gullies in the northern Shaanxi Loess Plateau. Four indices are used to examine the results, which show that the new algorithm is more suitable for loess terrain in simulating the spatial distribution of water accumulation, as well as in modeling the flow characteristics of the true surface by considering the morphological structures of the terrain. Copyright © 2013 John Wiley & Sons, Ltd.