Footpath morphology and terrain sensitivity on high plateaux: the Mamore Mountains,Western Highlands of Scotland

Variations in the morphology of a high‐level footpath are characterized using a new approach that relates footpath morphology to six terrain units defined jointly by two contrasting plant communities (U7 grass–heath communities dominated by Nardus stricta and Carex bigelowii, and U10 moss–heath communities dominated by Carex bigelowii and Racomitrium lanuginosum) and by the contrasting textural characteristics of underlying mineral soils developed on schist, granite and quartzite. All six terrain units are characterized by distinct footpath morphologies. The most critical factor affecting footpath morphology is the shear strength of the vegetation mat and underlying root zone. Vegetation mat shear strength was measured using a specially constructed shear rake. On all three lithologies, median shear strengths for U7 communities significantly exceed those for U10 communities, so that pathways on the former are significantly narrower and deeper than those developed on the latter. Adjacent zones of damaged or modified vegetation cover are also wider on U10 communities. The role of mineral soil (regolith) texture and thus underlying lithology in controlling footpath morphology is more complex. For soils with abundant fines, granite soils have lower shearing resistance than schist soils, and are associated with wider footpaths. Footpaths are also wide on clast‐supported quartzite regolith, which has high shearing resistance: pathways are trapezoidal in cross‐section in areas of U7 vegetation cover, but footpaths are very broad and diffuse in areas of U10 cover. Pathway depths are limited by increasing shear and compressive strength with depth. Implications of these findings for further research and management strategies are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

泥沙起动判别标准探讨

分析了现有起动标准的不足之处。在制定起动标准时,不但要考虑水流条件,还必须考虑泥沙颗粒在床面的相对位置。对同一粒径的泥沙颗粒,其起动条件不是一个常量,而是位于一个区间,它随颗粒在床面的相对暴露度而变化。根据力学原理,推导了泥沙颗粒起动时的临界无量纲切应力公式,并对其系数取值进行了理论计算。计算结果表明,对同一粒径、在同一起动状态下,泥沙颗粒的起动临界条件并非一个常量。并从理论上分析得到了临界值的范围,对个别及少量起动,其无量纲临界切应力为0.021～0.042及0.041～0.062。     

长乐—南澳断裂带东山段剪切变形与剪切加热作用

本文在系统的有限应变测量的基础上,对闽东南长乐—南澳断裂带东山段剪切变形特征进行了分析:利用变形石英显微亚结构。(动态重结晶颗粒)估算了剪切带内古应力并(σ—σ_3):通过对剪切变形能密度分布W(x)格离散化计算,采用有限差分数值近方法,获得了剪切热数值解:最后总结了研究地区剪切变形,剪切加热与动热成岩成矿作用的相对时空关系以及长乐—南澳断裂域构造意义     

新资深大断裂变质带特征、成因及活动演化

在前人研究成果和野外调查基础上,对新资深大断裂变质带特征进行系统总结,从宏观构造、显微构造与组构、岩石矿物学、年代学和地球化学等多学科角度综合研究,分析了新资断裂带各类岩石组构成因,并建立了其活动演化期次。新资深大断裂变质带构造岩主要包括定向组构系列岩石和块状系列岩石,主要是由早期的韧性变形变质作用阶段和晚期的脆性破碎作用阶段先后作用形成。越城岭岩体西侧规模巨大的花岗片麻岩带应属新资深大断裂变质带的一部分,属早期活动的产物,其原岩为越城岭岩体,为断裂变质和动力热流变质作用形成。韧性剪切系列岩石按变形变质强度可分为高温高压韧性剪切带和中温高压韧性剪切带,表明韧性剪切作用具有多期性。新资断裂带活动演化主要经历了四个阶段,始于加里东期,至喜山期均有活动,现在的新资断裂带是经过多个阶段不同类型变质作用由东向西不断迁移和相互叠加的结果。     

赤泥的变形-强度特性与结构性关系的研究

制铝工业排出的大量固体废料?--赤泥具有较强的结构性,笔者对其结构性及变形–强度特性进行了研究。根据饱和原状赤泥样及扰动样固结排水三轴剪切试验资料,用土力学方法分析了变形–强度特性与结构性之间的关系,探讨了结构性参数随轴应变及固结压力变化的规律。研究表明：（1）对浸水反应比较迟钝的饱和赤泥,用三轴试验条件下各应变水平原状样与扰动样的主应力差之比所表示的结构性定量化参数,来研究结构性对变形强度的影响可以得到良好的规律性。（2）结构性参数对固结周围应力反应敏感,不同固结周围压力和剪切应力对结构性的影响,主要发生在低应变区段内。(3)赤泥的变形–强度特性与其在形成过程中的固结应力大小及龄期长短没有直接的规律性关系,而与其在物理化学作用下结构性的强弱相关。     

青海省大柴旦红灯沟金矿区成矿条件与成矿模式研究

通过对南祁连岛弧带红灯沟矿床的形成背景、构造演化,以及金矿化研究分析认为,红灯沟矿区位于汇聚板块边缘最重要的金矿成矿带上,矿床赋存于一右行走滑韧性剪切带中。矿体主要发生在韧性剪切带中,构造变形越强,矿化越好。成矿物质为深部来源,可能与隐伏酸性岩体的成矿作用有关。后期的张性填充石英脉是重要的成矿构造。根据矿床的成因,建立了矿区成矿模式图,指出了有利的找矿部位。     

钢筋混凝土短肢剪力墙抗震性能试验研究

通过6片1：2单层短肢墙试体的低周反复荷戴试验,研究了在低周反复荷载作用下钢筋混凝土短肢剪力墙的整体工作性能、破坏形态及滞回特性。结果表明：试件的最终破坏均是由连梁失效引起的,连梁是短肢剪力墙结构的薄弱环节,因此,连梁的混凝土强度不应低于墙肢的混凝土强度,以免连梁出现粘结破坏;有翼墙的短肢剪力墙试体其延性系数都达到了3．5以上．其耗能能力较无翼墙短肢墙好。     

长江中下游地区暖区暴雨特征分析

利用2007到2013年5-9月间常规和非常规资料以及6 h一次的NCEP 1°×1°再分析资料,将长江中下游地区暖区暴雨按天气形势划分为冷锋前暖区暴雨、暖切变暖区暴雨以及副热带高压边缘暖区暴雨三种类型。统计表明暖区暴雨一般发生在距离切变线(锋线)100~300 km的暖区内。主要结论包括:(1)冷锋型降水强度偏弱且分布均匀,集中在5、6月;暖切变型发生次数最多且强度大,主要发生在6、7月长江中下游地区的偏南部;副热带高压边缘型发生次数最少但强度较大,发生在7、8月。暖区暴雨的发生次数及强度在大别山、皖南山区较为集中。(2)暖区暴雨中短时强降水贡献大。(3)冷锋背景下的暖区暴雨一般产生在锋前低压槽中,暴雨落区与高低空急流耦合有紧密联系;暖切变型以低层暖切变线为主要天气背景,地面常有弱静止锋,暖区对流活动与中尺度急流结构、地形强迫等因素存在较高的相关性;副热带高压边缘暖区暴雨与局地的水汽积累和对流不稳定条件的发展有密切关系。据此建立三类暖区暴雨的概念模型。     

冻融循环下花岗岩剪切蠕变试验与模型研究

为探讨冻融对寒区工程岩石剪切蠕变特性的影响,以吉林省辉白隧道花岗岩为研究对象,对经历不同冻融循环次数的试样开展细观特征分析和剪切蠕变试验。试验结果表明:(1)随着冻融次数的增加,试样裂隙、孔隙不断扩展,岩石表面损伤现象愈发明显;(2)试样主要以中小孔隙为主,孔隙度随着冻融次数的增加呈非线性增长趋势;(3)随着冻融循环次数增加,蠕变变形量和蠕变速率逐渐增大,而蠕变时长、破坏应力和长期强度均呈现明显降低趋势。根据试验结果,进行冻融岩石非定常蠕变参数的表达,提出了冻融岩石损伤黏性元件,构建了花岗岩冻融剪切蠕变本构模型。将蠕变试验曲线和理论模型拟合曲线进行对比,验证了模型的正确性和适用性。通过对蠕变参数进行敏感性分析,研究了其对花岗岩蠕变变形的影响,并给出了蠕变参数随冻融循环次数的变化规律。该研究结果对于寒区岩体工程长期稳定性评价具有指导意义。     

Effect of sand on the vacuum consolidation of dredged slurry

Vacuum preloading is often used to improve the geotechnical properties of dredged slurry. Although the performance of this method has improved with rapidly developing technology, soil columns usually formed on the drainage boundary induce the decrease of permeability around the boundary, thereby limiting the further development of this method. To address this issue, this paper proposes a method for pretreating the slurry combined with sand prior to vacuum consolidation. This method partially replaces the fine particles with sand to reduce the formation of soil columns. Two groups of vacuum preloading tests were performed to investigate the effect of sand content and sand grain size on the vacuum consolidation of dredged slurry. The test results revealed that for a given sand grain size, increasing the sand content of the sand–slurry mixture increased the pore water drainage and accelerated the dissipation of pore water pressure, thereby increasing the vane shear strength. In contrast, for a constant sand content, the samples containing coarse sand exhibited increased pore water drainage and accelerated dissipation of pore water pressure, thereby increasing the vane shear strength of the soil.