黄土高原丘陵沟壑区切沟侵蚀与地形关系分析——以纸坊沟流域为例

沟蚀是土壤侵蚀研究的主要内容之一,地形地貌是沟蚀的一个重要影响因子。本文以安塞纸坊沟流域作为研究区域,选择土地利用方式、土壤类型、坡度坡长因子、平面曲率、坡向和地形湿度指数6个因子,通过因子内切沟所占比重/整个研究区切沟所占比重计算各个因子的权重值,通过空间叠加分析土壤侵蚀敏感性,并通过重分类的方法把土壤侵蚀敏感性分为基本无侵蚀、轻度侵蚀、中度侵蚀、强度侵蚀、剧烈侵蚀5个等级,来研究切沟侵蚀与地形的关系。结果表明：切沟多发生在坡度坡长较大、地表湿度较高的林草地区域和更容易发生侵蚀的黄绵土区域,并且多分布在阴坡的凹面;对比分析切沟侵蚀和土壤侵蚀敏感性,切沟大多分布在中等侵蚀敏感性以上的区域,约占总切沟的90%;实验权重值对验证区冲沟的响应精度为82.43%（中度侵蚀及其以后阶段）,与实际值90.53%相差不大,说明此种方法对黄土丘陵沟壑区具有一定适用性,对黄土丘陵沟壑区水土保持工作有重要意义。     

The Effect of Internal Fluid on the Response of Vortex-Induced Vibration of Marine Risers

Based on Iwan‘s wake oseillator model developed with the classical van der Pol equalion, the differential equation for the response of the vortex-induced vihration (VIV) of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The effect of the intermal flowing fluid on the response of VIV of the riser is studied by means of the Finite Element Method. The results show that the effect of the internal fluid velocity on the VIV of the riser is strong when the natural frequency of the riser is close to the vortex shedding frequency. In addition, the increase of the top tension can decrease the sensitivity of the riser to the internal fluid velocity.     

县(市)绝对地震应急能力评估方法的初步研究

县(市)地震应急能力的高低直接关系到中国整个地震应急工作的成效.从县(市)绝对地震应急能力的内涵分析出发,结合汶川地震灾区县(市)地震应急能力实地调研工作取得的认识,首先初步构建了县(市)绝对地震应急能力指标体系框架;然后以四川省县(市)为例,在遵循科学性、系统优化和可操作性原则的基础上,构建了围绕着1个目标层,设定5...     

地震作用下黄土边坡动力响应数值分析

利用FLAC3D软件对某三级黄土边坡进行了动力反应分析。首先分析了静力作用下该黄土边坡剪应变增量和坡面、坡内、坡顶不同监测点的位移;在此基础上进行动力分析,得出黄土边坡地震动力响应规律。研究结果表明,静力作用下坡面上水平向位移明显大于垂直向位移,水平向位移从坡底向上逐渐减小;坡面处位移较大,位移在每级坡坡脚稍向上一定范围内达到最大值;地震作用下黄土边坡剪应变增量由坡脚稍向上部位开始向周围扩展,范围明显增大,且随地震持时的增加剪应变增量增幅较大;塑性区变化显示该黄土边坡坡顶以拉破坏为主,坡脚稍向上开始以剪破坏为主并伴有拉破坏。黄土边坡对地震波具有临空面放大效应,地震波在坡体内传播过程中还具有滞后效应     

Analysis on the Characteristics of the Coseismic Response of Water Levels Recorded in Three Wells in Hainan,China to the Two Sumatra-Andaman Strong Earthquakes

The characteristics of seismic water level fluctuations of the two Sumatra-Andaman strong earthquakes with magnitude 8.7 and 8.5 on December 26,2004 and March 29, 2005 recorded at Jiaji well, Qionghai, Hainan were analyzed, the features of the infrequent ＂step＂ changes of well water level after the two earthquakes were also analyzed and the mechanism of the ＂step change＂ of well water level was discussed. Then the high-sample-rate digital observation data of seismically-induced water level fluctuations of the Sumatra-Andaman strong earthquakes with magnitude 8.7 and 8.5 recorded at Nanbin well, Sanya and Tanniu well, Wenchang were analyzed. The results suggest that the dominant period of the seismic well water level fluctuation in all three wells was comparatively accordant, the amplitudes of seismic water level fluctuation of the same earthquake in different wells were clearly different, the time duration of seismic water level fluctuations of different earthquakes at the same well was also clearly different.     

Little River Experimental Watershed,a keystone in understanding of coastal plain watersheds

The US Department of Agriculture-Agricultural Research Service Southeast Watershed Research Laboratory (SEWRL) initiated a hydrologic research program on the Little River Experimental Watershed (LREW) in 1967. Long-term (52 years) streamflow data are available for nine sites, including rainfall-runoff relationships and hydrograph characteristics regularly used in research on interactive effects of climate, vegetation, soils, and land-use in low-gradient streams of the US EPA Level III Southeastern Plains ecoregion. A summary of prior research on the LREW illustrates the impact of the watershed on building a regional understanding of hydrology and water quality. Climatic and streamflow data were used to make comparisons of scale across the nine nested LREW watersheds (LRB, LRF, LRI, LRJ, LRK, LRO, LRN, LRM, and LRO3) and two regional watersheds (Alapaha and Little River at Adel). Annual rainfall for the largest LREW, LRB, was 1200 mm while average annual streamflow was 320 mm. Annual rainfall, streamflow, and the ratio between annual streamflow and rainfall (Sratio) were similar (α = 0.05) across LREWs LRB, LRF, LRI, LRJ, LRK, and LRO. While annual rainfall within the 275 ha LRO3 was found to be similar to LRO and LRM (α = 0.05), annual streamflow and Sratio were significantly different (α = 0.05). Comparisons of annual rainfall, streamflow, and Sratio between LRB and the regional watersheds indicated no differences (α = 0.05). Based upon this analysis, most regional watersheds shared similar hydrologic characteristics. LRO3 was an exception, where increases in row crops and decreases in forest coverage resulted in increased streamflow. LREW data have been instrumental in building considerable scientific understanding of flow and transport processes for these stream systems. Continued operation of the LREW hydrologic network will support hydrologic research as well as environmental quality and riparian research programs that address emerging and high priority natural resource and environmental issues.     

内蒙古阿贵庙地区地质构造演化与成矿响应探讨

阿贵庙地区位于狼山造山带的西段,同狼山成矿带东段的东升庙、炭窑口、霍各乞等大型-超大型铜铅锌多金属矿区具有相似的成矿地质背景和其他有利的成矿地质条件。笔者在分析区域构造地质背景的基础上,重点研究了阿贵庙地区的地质构造演化过程与成矿作用。研究结果表明:阿贵庙地区经历了古太古代基底岩石建造的形成、太古宙晚期-古元古代早期结晶基底形成和变质与变形、中元古代陆缘裂解与接受沉积-成矿、新元古代末裂陷槽闭合、晚古生代(海西期)-中生代(印支期)以来的挤压造山变形、大量岩浆上侵、地壳增生与变形的多个构造演化阶段。在不同的构造演化阶段形成不同类型的矿床:新太古代主要形成海底火山热水沉积条带状铁矿、在中元古代主要形成了与被动陆缘裂解过程相关的热水沉积硫化物矿床、晚古生代则形成与次火山岩浆热液成矿作用相关的斑岩型铜金矿床以及其他与火山岩有关的多个铜矿点。     

高烈度区大跨刚构-连续梁桥地震响应分析

为研究大跨刚构-连续梁桥在高烈度地区的地震响应,选取羊记沟左线大桥为工程背景,利用Midas软件建立多个有限元模型,考虑纵、横桥向的水平地震波输入,比较反应谱与时程分析结果,获得结构动力响应特点,为大跨刚构-连续梁桥的抗震设计提供参考依据。结果表明:刚构-连续体系仅单墩刚构时不宜采用反应谱分析,高烈度地区桥梁进行地震响应时程分析时,选用与场地适应的地震波的同时,应考虑采用本地地震参数转化人工波作为地震激励源。桥墩不等高时,可通过改变墩截面形状及其与主梁连接方式调节内力分布,避免矮墩刚度大导致的内力集中。     

尼泊尔地震灾害及应急救援

介绍了2015年4月25日尼泊尔发生的MS8.1地震灾害、受灾国政府应急响应、国际应急响应以及我国西藏受灾区应急救援的情况。总结了尼泊尔地震灾害和应急救援的经验与教训。     

Confined aquifer as wave-guide and its responses to geo-acoustic waves

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