DEM resolution dependencies of terrain attributes across a landscape

This paper documents resolution dependencies in terrain analysis and describes how they vary across landform location. Six terrain attributes were evaluated as a function of DEM resolution—slope, plan curvature, profile curvature, north–south slope orientation, east–west slope orientation, and topographic wetness index. The research highlights the effect of varying spatial resolution through a spatial sampling/resampling scheme while maintaining sets of indexed sample points at various resolutions. Tested sample points therefore coincide exactly between two directly compared resolutions in terms of their location and elevation value. An unsupervised landform classification procedure based on statistical clustering algorithms was employed to define landform classes in a reproducible manner. Correlation and regression analyses identified sensitive and consistent responses for each attribute as resolution was changed, although the tested terrain attributes responded in characteristically different ways. These responses displayed distinguishable patterns among various landform classes, a conclusion that was further verified by a series of two‐sample, two‐tailed t‐tests.     

Reinforcement effects of ground treatment with dynamic compaction replacement in cold and saline soil regions

The mechanical property of saline soils varies with moisture and climate in the cold and salt lake region of Qinghai-Tibet Plateau, which influences project construction. In order to improve foundation reinforcement effect of the Qarhan–Golmud Highway, Qinghai Province, China, dynamic compaction replacement (DCR) composite foundation was applied in saline soils. A field experiment was conducted in this area, where strength and working mechanism of pier-soil and deformation modulus of the composite foundation was analyzed after reinforcement. This paper presents methods for determining the coefficient on the bearing capacity evaluation and deformation modulus of composite foundation with DCR. Reinforcement case of DCR is highly effective in saline soils of the salt lake regions, which helps the migration of water and salt in saline soils.     

现浇X形混凝土桩沉桩挤土效应现场试验研究

挤土型桩的挤土效应一直是工程界研究和关注的热点问题之一。结合南京长江四桥北接线段现浇X形桩软基处理工程,首次开展现浇X形混凝土桩（简称X形桩）沉桩过程现场试验,测得不同X形横截面方向、不同距离及深度处的水平位移、侧向土压力以及孔隙水压力的分布规律,研究X形桩挤土效应规律。研究结果表明,最大水平位移发生在桩顶,距离5倍等效桩径处的土体水平位移可以忽略不计;随着桩中心距的增加,挤土压力和孔隙水压力逐渐减小,并且尖角方向的挤土压力大于凹弧方向的挤土压力。现场试验数据为X形桩的布置形式以及桩间距的选择提供有力的设计参考依据。     

城市创意旅游资源空间效应及发展模式——以苏州市中心城区为例

随着创意经济的兴起和旅游者需求的变化,发展创意旅游日益成为消费热点和推动旅游业转型升级的有效途径。创意旅游资源是创意旅游发展的基础,其产生的空间效应是区域旅游研究的重要内容,对提升区域旅游竞争力具有重要意义。以苏州中心城区为例,综合运用最近邻指数、不平衡指数、核密度分析和使用者温度计量模型等方法,深入研究城市创意旅游资源空间效应。结果显示：① 创意旅游资源的融入使苏州中心城区整体和各区域的旅游资源空间分布集聚度增大,但各区域增大程度和资源空间分布状态变化不同;② 融入创意旅游资源后苏州中心城区整体旅游资源区域分布呈集中态势,且分布的均衡度降低;③ 创意旅游资源的融入促进了区域旅游资源空间效应的发挥,苏州中心城区由以姑苏区为“单核心”的“众星拱月”空间格局转变为以姑苏区—工业园区为“双核心”的“日月同辉”空间格局,从而实现苏州中心城区“双核”旅游空间发展模式。     

高立式阻沙网的阻沙效果对比

设计了高120cm的4种结构HDPE阻沙网：均匀结构阻沙网（a）、大条带上疏下密式阻沙网（b,60cm宽条带）、小条带疏密相间式阻沙网（c,20或10cm宽条带）和中条带上密下疏式阻沙网（d,40cm宽条带）,布设在塔克拉玛干沙漠腹地的垄间平地。阻沙试验结果表明：（1）4种结构阻沙网积沙纵断面的蚀积形态均呈单峰,但积沙宽度和高度不同,3种非均匀结构的阻沙网积沙高度均高于均匀结构阻沙网,积沙高度c> b> d> a。（2）4种结构阻沙网积沙量c> a> b> d,积沙量均集中在下风侧分布,但b和c阻沙网积沙在上风侧的积沙量高于a和d阻沙网。（3）不同结构阻沙网积沙量及其空间分布差异主要与阻沙网结构的特殊风场结构有关。     

文化产业空间尺度效应研究——以西安市为例

以西安市为例,利用绕城高速内文化企业空间点数据,借助ArcGIS 9.3软件创建不同尺度方格网并计算格网内文化企业点数和密度,运用基尼系数、Global Moran's I指数和Kriging插值来探讨文化产业空间尺度效应。结果表明：① 研究尺度的增大对文化企业空间集中程度具有“稀释”作用,稀释能力随着尺度的增大而减弱,这种稀释作用具有一定的尺度“阈值”;② 格网尺度超过1.5 km×1.5 km时,集中程度随尺度变化较小;③ 根据基尼系数和Global Moran's I指数的变化情况,将文化产业空间分为三个尺度层次,微观尺度（0.1 km×0.1 km~0.6 km×0.6 km）下自相关系数随尺度增大而快速增大,中观尺度（0.6 km×0.6 km~2.8 km×2.8 km）下高水平波动,宏观尺度（2.8 km×2.8 km以上）下趋于稳定;④ 从微观到宏观尺度,文化产业沿着散点—极核—轴带—团块格局演变,文化产业的尺度效应是由空间单元划分引起相邻文化密集区的空间重构造成的;⑤ 研究的实践意义在于,进行文化产业规划和制定相关政策时,应针对文化产业不同尺度的空间特征做出不同层次的安排,以利于文化产业的合理布局和健康发展。     

基于SPH-FEM耦合法的土体爆炸效应数值研究

岩土体爆炸破坏问题是岩土工程领域的研究热点,为开展小当量集团装药在不同埋置深度时的土中爆炸效应分析研究,在LS-DYNA框架内建立基于光滑粒子流体动力学-有限元耦合方法（SPH-FEM）的砂土地基爆炸效应分析模型。计算结果表明：浅埋装药时最大爆坑深度到达时刻远在最大爆坑直径之前,地基表层砂土体剪切流场对爆坑直径的发展具有决定性作用;随着药包埋置深度的增加存在一个临界爆坑直径,爆坑直径近似认为只与药包当量和埋置深度相关,经简化与经验假定之后得到的爆坑直径与埋药深度之比与比例距离近似呈直线关系;砂土中爆炸波在近区表现为强间断的冲击波形式,压缩作用是造成近区砂土大变形流动的主要因素,而在爆炸远区则转变为连续的应力波形式;土中爆炸波峰值压力随比例爆距的衰减规律与经验曲线基本一致。研究结果可以为地基工程的抗爆设计及加固提供参考。     

Analysis of the role of diffraction in topographic site effects using boundary element techniques

The role played by the diffraction field on the problem of seismic site effects is studied. For that purpose we solve and analyze simple scattering problems under P and SV in-plane wave assumptions, using two well known direct boundary-element-based numerical methods. After establishing the difference between scattered and diffracted motions, and introducing the concept of artificious and physically based incoming fields, we obtain the amplitude of the Fourier spectra for the diffracted part of the response: this is achieved after establishing the connection between the spatial distribution of the transfer function over the studied simple topographies and the diffracted field. From the numerical simulations it is observed that this diffracted part of the response is responsible for the amplification of the surface ground motions due to the geometric effect. Furthermore, it is also found that the diffraction field sets in a fingerprint of the topographic effect in the total ground motions. These conclusions are further supported by observations in the time-domain in terms of snapshots of the propagation patterns over the complete computational model. In this sense the geometric singularities are clearly identified as sources of diffraction and for the considered range of dimensionless frequencies it is evident that larger amplifications are obtained for the geometries containing a larger number of diffraction sources thus resulting in a stronger topographic effect. The need for closed-form solutions of canonical problems to construct a robust analysis method based on the diffraction field is identified.     

山东省生态地球化学调查与评价综述

自2002年开展生态地球化学调查以来,山东省生态地球化学调查已覆盖全省陆域和部分近岸海域,面积161370km2。该文介绍了山东省生态地球化学调查评价的基本情况和方法技术,并以获取的海量地球化学数据为基础,对多目标区域地球化学调查、区域生态地球化学评价成果进行了系统总结,为山东省社会经济发展提供了基础平台。