A new model for the vibration isolation via pile rows consisting of infinite number of piles

In this study, on the basis of the Floquet transform method, a numerical model for the simulation of the vibration isolation via multiple periodic pile rows with infinite number of piles is established. By means of the fictitious pile method due to Muki and Sternberg, the second kind of Fredholm integral equations for the pile rows are developed by using the fundamental solutions for the half‐space and the compatibility conditions between the piles and half‐space. Employing the Floquet transform method, integral equations for the pile rows in the wavenumber domain are then derived. Solution of the integral equations yields the wavenumber domain solution for the pile rows. The space domain solution can then be retrieved by inversion of the Floquet transform. Numerical results show that the proposed model with the Floquet transform method is in a good agreement with those of the conventional direct superposition method. On the basis of the new model, influences of the spacing between neighboring piles, the Young's modulus of the piles, and the pile length on the vibration isolation effect of the pile rows are investigated. Numerical simulations conducted in this study show that compared with the direct superposition method, the efficiency of the proposed model for simulation of the vibration isolation via pile rows is very high. Copyright © 2012 John Wiley & Sons, Ltd.     

高阶非线性完全频散性波浪数值模型及应用

为更精确地模拟强非线性完全频散性波浪的传播,采用长波上非线性重力表面波传播高阶数学模型,综合参考此模式已有的研究成果,建立了一个高达五阶的完全频散性非线性数值模型。应用该五阶模式对斜坡地形、潜堤地形及正弦沙链地形进行模拟计算,并与已有的实验资料进行对比,结果显示五阶模式较低阶模式模拟结果的精度上有了明显提高,模拟波形与实验结果吻合度良好,证明高阶模式更适用于高频散高非线性波浪传播的数值模拟。     

Processes of the deposition and vicissitude of Mu Us Desert, China since 150 ka B.P.

“Milanggouwan stratigraphical section” named lately takes down 27 cycles of alternately evolutionary histories of desert depositions in the Mu Us area with the fluviolacustrine facies and palaeosols since 150 ka B. P. Studies show that the sedimentary form was induced by the growth and decline and confrontation each other between the winter monsoon and the summer monsoon of East Asia in the past 150 ka. Project supported by the National Natural Science Foundation of China (Grant No. 49473192).     

Variation in the vertical zonality of erodibility and critical shear stress of rill erosion in China's Hengduan Mountains

Soil erodibility is an essential parameter used in soil erosion prediction. This study selected the Liangshan town watershed to quantify variation in the vertical zonality of rill erodibility (k_r) in China's ecologically fragile Hengduan Mountains. Soil types comprised of yellow–brown (soil A), purple (soil B), and dry-red (soil C) in a descending order of occurrence from the summit to the valley, which roughly corresponds to the vertical climate zone (i.e. cool-high mountain, warm-low mountain, and dry-hot valley sections) of the study area. With elevation, vertical soil zonality varied in both soil organic matter (SOM) content and soil particle-size fractions. A series of rill erosion-based scour experiments were conducted, using water discharge rates of 100, 200, 300, 400, 500, and 600 mL min^-1. Additionally, detachment rates (Dr) were measured under three hydrological conditions (the drainage, saturation, and seepage treatments). Results show that both Dr and flow shear stress (Ʈ) values increased as discharge increased. As elevation increased, the k_r values decreased, while the vertical zonality of critical shear stress (Ʈ_c) values showed no obvious variation. The highest k_r values were observed during the seepage treatment, followed by the saturation treatment then drainage treatment, indicating that variation in vertical hydraulic gradients could significantly alter k_r values. This study also found that land-use types could also alter k_r and Ʈ_c values. Further research, however, is necessary to better quantify the effects of subsurface hydrological conditions and land-use types on k_r under different soil zonalities in China's Hengduan Mountains. © 2018 John Wiley & Sons, Ltd.     

基于区域自动站数据的兰州地区降水精细化特征

基于2012—2019年兰州地区146个区域自动气象站小时降水数据,从不同时间尺度分析兰州地区近8 a降水精细化特征。结论如下:(1)2012—2019年,兰州地区年均降水量总体呈"北少南多、外多内少"的空间分布特征;年降水量具有明显的年际变化,2018年降水异常偏多46%,而2015、2017年降水异常偏少,尤其2015年偏少30%。(2)兰州地区降水主要集中在7—8月,受环流形势影响,7—8月南部降水明显多于北部,其余月份南北降水差异不明显。(3)兰州地区降水量和降水范围分别表现为"朝少夕多"、"夜大日小"的日变化特征;受海拔高度影响,城区降水量总体比山区小,且因热岛效应,城区降水主要集中在午后至傍晚前后,多为对流性降水,而山区降水日分布较为均匀,整体日波动较小。(4)安宁区短时强降水发生频次最高,但短时强降水频发的站点出现在皋兰县六合站和永登县徐家磨村站,永登县是兰州地区短时强降水预报需重点关注的地区。     

地铁车站与横跨桥梁耦联破坏数值模拟

以典型的两层三跨形式地铁车站为研究对象,采用非线性动力时程反应分析方法,对软土场地的地铁车站与上部交叉桥梁模型进行数值模拟分析,给出了一种潜在的地铁车站-桥梁耦联破坏模式,分析了地铁车站与上部桥梁的地震动力相互作用.数值模拟结果表明:桥梁对车站的地震响应影响较小,车站发生破坏主要取决于地震作用及其本身的强度;地铁车站发...     

长江宜昌段水系沉积物镉高值带成因

应用贡献因子和富集因子等方法对长江宜昌段水系沉积物Cd的来源进行研究,结果表明：研究区内地层对宜昌段水系沉积物Cd的贡献由大到小依次为：震旦系>二叠系>泥盆系>志留系;前震旦系、寒武系、奥陶系、三叠系、侏罗系和白垩系地层则对长江宜昌段Cd高值带的形成有一定的削弱作用。利用贡献因子、富集因子和MapGIS空间分析综合研究表明,震旦系和二叠系含矿富Cd地层的风化产物是长江宜昌段Cd高值带的主要自然来源。区内锌矿、煤矿和磷矿开采过程中的尾砂、废水的堆积和排放是长江宜昌段Cd高值带的重要人为污染源。     

Paleostress Reconstruction of Micangshan Anticlinorium on the Southern Margin of the Qinling Orogenic Belts, China

Brittle structures in rock of different ages can be used to establish the tectonic evolution of an orogenic belt through paleostress calculations. Micangshan is located at the southern margin of the Qinling orogenic belt,between the SE-trending Longmenshan fold-and-thrust belt and the arcuate Dabashan thrust-and-fold belt. Structural observations revealed that the dominant structures are reverse and strike-slip faults and folds with E–W and NE–SE trends. To increase knowledge of the tectonic evolution of the Micangshan anticlinorium,faults,joints,veins,and folds were measured at more than eighty sites. On the basis of structural analysis,it emerged that the multiphase paleostress fields became established after the oblique collision between the North and South China plates. The earliest stress field with N–S compression was established during the Micangshan uplift associated with the E–W trending faults and folds. Subsequently,a N–S extension occurred when the Qinling orogenic belt collapsed. Then NW–SE compression developed,with NE trending faults and folds forming in relation to Longmenshan thrusting toward southwest on the eastern margin of the Tibetan plateau. With the development of the arcuate Dabashan orogenic belt,the compression stress orientation of the Micangshan anticlinorium altered from NE–SW to E–W.     

白河黄石板铅锌矿的热水沉积岩及找矿潜力

经过对黄石板铅锌矿含矿层展布、产态、矿化富集规律等基本特征的总结,以及对含矿层中典型热水沉积岩岩石学特征、岩石化学特征、含矿物质来源初步分析,通过热水沉积岩和盆地正常水沉积围岩的稀土元素地球化学等与南秦岭泥盆纪热水沉积岩的对比、研究,初步认为白河县黄石板铅锌矿为一较典型的热水沉积矿床。提出黄石板矿区西段高家沟一带深部仍存在隐伏矿体的可能性较大,并通过钻探验证发现较富隐伏铅锌矿体。运用热水沉积成岩成矿理论指出该地区找矿方向。     

Application of passive source surface-wave method in site engineering seismic survey

Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the passive source surface-wave method is introduced into the site engineering seismic survey and practically applied in an engineering site of Shijingshan District. By recording the ubiquitous weak vibration on the earth surface, extract the dispersion curve from the surface-wave components using the SPAC method and obtain the shear-wave velocity structure from inversion. Over the depth of 42 m underground, it totally consists of five layers with interface depth of 3.31, 4.50, 7.23, 17.41, and 42.00 m; and shear-wave velocity of 144.0, 198.3, 339.4, 744.2, and 903.7 m/s, respectively. The inversion result is used to evaluate site classification, determine the maximum shear modulus of soil, provide basis for further seismic hazard analysis and site assessment or site zoning, etc. The result shows that the passive source surface-wave method is feasible in the site engineering seismic survey and can replace boreholes, shorten survey period, and reduce engineering cost to some extent.