High spatial resolution mapping of surface velocities and depths for shallow overland flow

Point measurements of flow rate, depth or velocity are not sufficient to validate overland flow models, particularly when the interaction of the water with the soil surface creates a complex flow geometry. In this study, we present the coupling of two techniques obtaining spatial data of flow depths and surface velocity measurements for water depths as low as 1 mm. Overland flow experiments were performed in the laboratory at various flow rates and slopes on two surfaces. The first surface was 120 cm by 120 cm showing three undulations of sinusoidal shape with an amplitude of 1 cm and a wavelength of 20 cm, while the second was a 60 cm by 60 cm moulded reproduction of a seedbed with aggregates up to 2 cm in size. Large scale particle image velocimetry (LSPIV) was used for velocity measurements with a sub‐centimetre spatial resolution. An instantaneous‐profile laser scanner was used to map flow depths with a sub‐millimetre spatial resolution. A sensitivity analysis of the image processing of the LSPIV showed good robustness of the method. Comparison with measurements performed with hot film anemometer and salt velocity gauge showed that LSPIV surface velocities were representative of the flow. Water depths measured with the laser scanner were also in good agreement with single‐point measurements performed with a dial indicator. Spatially‐distributed flow rates could be computed by combining both presented techniques with a mean relative error less than 20%. Copyright © 2012 John Wiley & Sons, Ltd.     

The proportions and variations of the light absorption coefficients of major ocean color components in the East China Sea

The East China Sea (ECS),one of the largest continental seas,has dynamic hydrology and complex optical characteristics that make ocean color remote-sensing retrieval difficult.The distributions and proportions of the light absorption coefficients of major ocean color components based on two large-scale investigations in the ECS are presented,showing these features in typical summer and winter seasons.The absorption coefficient a CDOM,a NAP and a phy of colored dissolved organic matter,non-algal particle,and pigment of phytoplankton show a decreasing trend from the coast to the outer shelf.According to the a CDOM distribution at 440 nm,the Changjiang River plume shows an abnormal southeastward transport.An extremely high a NAP value patch at 440 nm is present in the middle coast.The chlorophyll-a-specific phytoplankton pigment absorption (a phy) is much higher in winter than in summer,which may cause serious underestimated results when applying the averaged a phy into remote-sensing algorithms for chlorophyll concentration retrieval.The importance of phytoplankton size was evident in outer shelf waters.The absorption of a CDOM (440) is a dominant component accounting for over half of the total seawater absorption in summer.The a NAP (440) accounts for 64% of the absorption of the ECS coastal area in winter.     

基于粒子群双重空间聚类的城镇地价空间分异规律挖掘

城镇地价的空间分异对其动态监测片区划定具有重要的参考作用,而空间聚类则是对该问题进行分析的一种有效方法.文中在分析空间聚类本质的基础上,设计了一种基于样本数据的粒子群双重空间聚类挖掘模型,并以北海市二手房地价空间分布挖掘为实例进行了应用.结果表明:粒子群双重空间聚类在空间聚类效果上优于传统K-均值聚类法,尤其是对于任意形状聚类簇的挖掘;然而,由于标准粒子群优化算法机理的限制,其聚类效果随聚类中心的增多而呈下降趋势.总体而言,该方法能利用有限的样本挖掘质量较好的城镇地价空间分异区,可为城镇地价动态监管提供相     

Stress-strain analysis of loess triaxial shear test by PFC3D

In order to compensate for limitations of microscopic study on loess triaxial tests, taking the loess in Longxi area as an example, the authors established the loess triaxial test model by using PFC3D software and simulating tfiaxial shear test under the different confining pressures in 0 kPa, 50 kPa and 300 kPa. Compared with laboratory triaxial shear test, the numerical simulation test has a guiding role in loess mechanical strength analysis.     

主动侧向受荷桩桩周土的影像观测与数值模拟

在室内模型试验中对模型桩顶施加水平荷载,分别采用数字照相无标点变形量测系统及配套量测分析软件形象地再现了不同密实度砂土中桩周土体及地表土体水平位移分布规律。对双桩的地表水平位移分布情形进行观测分析,结合桩顶位移与水平荷载的关系研究了桩间距对桩与桩之间的相互作用的影响。应用颗粒流程序PFC2D模拟一定深度平面内桩周土体位移,揭示了主动桩桩周土的颗粒流动性状及桩间距对桩-土相互作用的影响。结果表明,主动受荷桩桩周砂土位移场呈两个纺锤体状;砂土密实度增加,桩前砂土变形范围增大;桩间距越小,相邻桩相互影响越明显。     

扩底抗拔桩桩端阻力的群桩效应研究

通过颗粒流数值模拟,从桩端阻力随上拔位移的发展与桩端周围土体颗粒位移表现等角度,研究了扩底抗拔桩端阻力的群桩效应问题。研究比较了单桩（墩）与群桩（墩）的抗拔性状以及不同墩距下中心墩与边墩阻力随上拔位移发展的情况。研究表明,在归一化上拔量 0.1时,单桩（墩）与群桩（墩）的上拔特性无明显差别;此后,随着上拔位移的发展,单桩（墩）的上拔端阻力要大于群桩中的桩（墩）的端阻力,桩（墩）周围土体颗粒的相互影响开始显现。在归一化上拔量 0.5的情况下,群桩（墩）中中心桩（墩）的端阻力要略大于边桩（墩）。在归一化上拔量 0.5的情况下,群桩中边桩的桩端阻力较中心桩的要大,而群墩中边墩的墩端阻力较中心墩要小,体现了桩身侧限对抗拔桩群中端阻力发挥的影响。随着墩距的增大,在较大的位移量以后群墩才与单墩的受力有显著差别。     

不同填充及加载路径下劈裂砂岩渗流特性研究

采用劈裂宜昌砂岩,对中细砂、粗砂及混合砂砂粒填充条件下加载路径、轴压、围压、填充物颗粒粒径及填充物厚度对渗流速度的影响规律进行探讨。研究结果表明,在不同填充物一定的应力情况下,加力路径发生变化,渗流速度也发生变化,这是工程中测量渗流数据离散的原因之一;轴压与渗流速度成线性关系,当围压?3≤1.5 MPa时,围压对渗流的影响较大,当?3＞1.5 MPa时,围压对渗流的影响极小;粒径与渗流速度呈单调递增关系,围压对无填充物的影响大于对有填充物的影响;渗流速度与填砂厚度在一定范围内呈现指数递增关系、研究中给出特定条件下轴压围压与渗流速度的定量分析公式。     

努尔苏丹樟子松人工林土壤粒度组成特征研究

为了揭示努尔苏丹不同林龄樟子松人工林对土壤粒度组成的影响,通过野外采样与室内分析相结合,分析了努尔苏丹周边不同林龄樟子松人工林土壤粒度与分形维数特征,研究了分形维数与土壤特性之间的关系.结果表明:(1)研究区土壤粒度组成以粉粒为主,砂粒次之,黏粒最少,樟子松人工林的种植能够显著提升土壤表层细颗粒物质含量.不同林龄人工林...     

轻量土及其在工程中的应用

轻量土可以分为发泡聚苯乙烯(EPS)块、发泡颗粒混合轻量土、气泡混合轻量土(FCB)和次生材料混合轻量土4种类型.根据其湿密度的不同,又可以将轻量土分为超轻量土、轻量土和准轻量土3个大类.由于轻量土具有轻量性、自立性、流动性、隔热性、耐水性、耐久性等特性,可以大幅度减小上部荷载和土压力.因此,在软土地基、山区陡峻斜坡的路基、桥涵等工程中得到了广泛的应用.在目前的实际设计和施工中,轻量土的设计可以参照国外的有关规程或手册.     

刚体地球CIP轴的极移和岁差章动

基于刚体地球极移和章动的联合动力学方程。给出了CIP轴的极移、岁差章动动力学方程,在顾及到5阶岁差章动力矩的情况下,给出了CIP轴的岁差章动表达式。通过推导发现。奇数阶引潮力位产生的岁差章动力矩使得黄经章动和交角章动出现了异向项(即：黄经章动出现了cos项,交角章动出现了sin项)。