土工带加筋碎石土的抗剪强度特性研究

大型三轴固结排水剪切试验表明：土工带加筋后土体的破坏强度和破坏应变均得到提高。从加筋土和未加筋土的强度包线看出,加筋前后土体的强度曲线基本平行,摩擦角相等,粘聚力提高。通过分析加筋土的应力-应变关系试验曲线,研究土工带加筋素碎石土的抗剪强度特性,提出土工带加筋土的抗剪强度表达式。为进一步研究土工带素碎石土加筋机理提供试验基础。     

冻融循环作用下宽级配砾质土的渗透特性

针对西北地区特殊的气候条件和砾质土料源丰富的实际情况,提出采用宽级配砾质土代替黏土作为土工合成材料膨润土垫(GCls)的保护层共同构成垃圾填埋场复合防渗系统的构想。文中选取宁夏银川地区冲-洪积作用形成的天然砾质土料,经人工掺和制配成满足规范对GCls防渗垫保护层渗透系数要求的宽级配砾质土样,在实验室对该土样进行了冻融循环作用下的渗透性能试验研究。结果显示,随着冻融次数的逐渐增加,土样的冻胀率逐渐变大,渗透系数也相应增大,经过12次冻融循环后,渗透系数约增大1～2个数量级;冻融循环初期,冻融作用对土样的影响最为剧烈,随着冻融循环次数的增加以及时间的延续,土样性状逐渐趋于稳定。由于宽级配砾质土对冻融循环作用的敏感性小于粉质黏性土,故采用宽级配砾质土作为Cls/GM的保护层共同组成填埋场复合防渗系统是值得期待的。     

准噶尔盆地北缘山前带沉积物源及相模式研究--以哈拉阿拉特山前缘春晖探区为例

准噶尔盆地北缘山前带是我国目前油气勘探的一个重点领域.为了深入探讨山前带沉积研究中存在的疑问,以准北缘哈拉阿拉特山山前春晖探区为对象,综合利用岩芯、钻测井资料及大量沉积学实验手段,对其侏罗系八道湾组沉积特征及物源方向进行研究,证实了该区粗碎屑沉积物主要来自北西方向的哈山山区,属于典型的近源沉积.通过构造、沉积演化史分析与现代沉积考察相结合的方法,总结出了山前带近源砾石高磨圆度的两类成因,分别对应于砾石形成期的滨海环境以及再搬运沉积期的湿地扇环境,最终建立了春晖探区八道湾组湿润型冲积扇沉积相模式.     

Medium‐term fluvial island evolution in a disturbed gravel‐bed river (Piave River,Northeastern Italian Alps)

River islands are defined as discrete areas of woodland vegetation surrounded by either water‐filled channels or exposed gravel. They exhibit some stability and are not submerged during bank‐full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30‐km‐long reach of the gravel‐bed Piave River, which has suffered from intense and multiple human impacts. Plan‐form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI > 200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI > 10 years, as well as a change in the human management relating to the control of gravel‐mining activities. The narrowing trend (1960–1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands.     

基于GIS的小麦赤霉病气象等级预报系统的设计与实现

以江苏省为例,介绍了基于地理信息系统的小麦赤霉病气象等级预报系统的设计思路及核心技术。系统采用VB.Net 2005和ArcEngine做为开发平台,基于MSSQL SERVER 2005数据库查询,利用日平均相对湿度、日平均气温和日照时数3个气象要素,用两种算法来计算小麦赤霉病发生发展的气象等级,生成包含地理信息的文字产品和图形产品,实现了小麦赤霉病气象等级业务预报。系统具有功能强大,算法高效,操作简单等特点,解决了业务部门资料分析处理和赤霉病气象等级预报的相关问题,具有很好的业务应用和推广价值。     

来自东南极西福尔丘陵附近冰碛物中沉积岩砾石的碎屑锆石LA-ICP-MS U-Pb年龄及其意义

东南极西福尔丘陵东南侧分布着长约20 km带状冰碛物,这些冰碛物成分复杂,其中含有少量与该地区高级片麻岩的基岩显著不同的沉积岩砾石.根据冰川流动方向可以推测它们来自西福尔丘陵的东南侧的冰盖之下.对其中8个具有代表性的沉积岩砾石样品进行碎屑锆石LA-ICP-MS U-Pb年龄测试,其U-Pb表面年龄主要集中在2410～2...     

A two‐dimensional morphodynamic model of gravel‐bed river with floodplain vegetation

Artificially straight river channels tend to be unstable, and ultimately develop into river meanders through bank erosion and point‐bar deposition. In this paper account is taken of the effects of riparian and floodplain vegetation on bank strength, floodplain flow resistance, shear stress partitioning, and bedload transport. This is incorporated into an existing 2D hydrodynamic‐morphological model. By applying the new model to an initially straight and single‐threaded channel, the way that its planform and cross‐sectional geometry evolve for different hydraulic and floodplain vegetation conditions is demonstrated. The results show the formation and upstream migration of gravel bars, confluence scouring and the development of meandering and braiding channel patterns. In cases where the channel becomes unstable, the instability grows out of bar formation. The resulting braiding patterns are similar to analytical results. The formation of a transition configuration requires a strong influence from vegetation. Copyright © 2010 John Wiley & Sons, Ltd.     

Controls on late Quaternary incised‐valley dimension along passive margins evaluated using empirical data

Incised valleys are canyon‐like features that initially form near the highstand shoreline and evolve over geological time as rivers erode into coastal plains and continental shelves to maintain equilibrium‐gradient profiles in response to sea‐level fall. Most of these valleys flood during sea‐level rise to form estuaries. Incised‐valley morphology strongly controls the rate of creation of sediment accommodation, valley‐fill facies architecture and the preservation potential of coastal lithosomes on continental shelves, and affects coastal physical processes. Nonetheless, little is known about what dictates incised‐valley size and shape and whether these metrics can be used to explain principal formation processes. The main control on alluvial channel morphology over human time scales is discharge; this is based on numerous empirical studies and is well‐constrained because all variables are easily measured at this short time scale. Knowledge of long‐term river evolution over a complete glacio‐eustatic cycle, on the contrary, remains largely conceptual, experimental and based on individual systems because variables that are thought to drive morphological change are not easily quantified. In spite of this difficulty, existing models of incised‐valley formation at the coast suggest that valley evolution is driven largely by downstream forcing mechanisms, highlighting sea‐level and shelf gradient/morphology as the dominant controls on valley incision. Although valleys are cut by rivers, whose channels are a direct reflection of discharge, little empirical data exist in coastal areas to address the degree to which valley evolution is governed by upstream controls. The late Quaternary is the best time period to examine because it provides the most complete sedimentary record and many variables, including sea‐level, tectonics, substrate lithology and drainage network characteristics, are accurately constrained. Here, 38 late Quaternary valleys along the coast of two different passive continental margins are compared, which suggests that valley shape and size are governed primarily by upstream, intrinsic controls such as discharge. Valley width, depth and cross‐sectional area are found to be predictable at the highstand shoreline and are scaled with the size of their drainage basin, which has important implications for estimating sediment discharge to continental shelves and deep water environments during periods of low sea‐level.     

砂卵砾石层倒垂孔施工技术

针对砂卵砾石层倒垂孔施工中钻孔偏斜、孔内坍塌掉块、取心以及保护管的安装等困难问题,从钻机安装、钻具结构、设备能力、钻进技术参数等多方面采取相应的技术措施,取得了良好的施工效果。介绍了红叶电站砂卵砾石层倒垂孔的施工技术。     

探地雷达在淡水区浅水域的探测试验

通过堤防护岸水域抛石探测、水下砼格及碎石层探测、江边堆场滑坡水域探测三个案例,说明探地雷达在淡水区浅水域探测效果。重点分析了探测对象所处环境的电导率、介电常数和探测所采用天线频率对探测效果的影响。探地雷达填补了浅水域工程勘察空白,研究成果对非水域探地雷达探测与检测具有借鉴意义。