On the shape and migration speed of a proto‐dune

The shape and migration speed of a proto‐dune are mathematically discussed. The migration speed of a low dune is shown to be inversely proportional to its wind‐directional length. Proto‐dunes, whose wind‐directional lengths are about 10 m, are expected to migrate at finite speeds. Copyright © 2002 John Wiley & Sons, Ltd.     

深海浅地层剖面特征及其与多金属结核富集度的关系

对东太平洋 Ｃ Ｃ 区内 １ 万多公里的浅地层剖面探测资料进行了统计分析, 并对深海浅地层剖面特征及其与多金属结核丰度的关系作了研究, 结果表明： 多金属结核的富集度与海底声反射率呈正比关系, 影响和控制结核丰度的主要因素是海底地形。一般透明层愈厚, 结核愈富集, 但不是对应关系; 层状层或散射层发育, 则多金属结核富集, 反之则不富集     

瓦店遗址地层记录的龙山晚期古环境与人类活动

龙山晚期是中华文明酝酿形成的关键时期,位于颍河上游的瓦店遗址文化层较完整地记录了这一时期的环境特征和人类活动。文章测定了瓦店遗址龙山文化晚期遗址地层沉积物的粒度、常量元素、磁化率和木炭屑密度等环境指标;结果表明,龙山晚期的下段地层(约4.2~4.1 kaBP)的炭屑密度指标(M/F比值)处于高值区间、Cr/Cu值较低,Pb、Cu元素含量较高、粒度频率分布的细尾端为单峰曲线,表明该时期气候干旱但农业活动相对活跃,但地层沉积动力主要为洪积作用。龙山晚期的上段(约4.1~3.9 kaBP)Cr/Cu值较高,Pb、Cu含量下降,炭屑的M/F值走低,沉积物频率曲线的细粒端出现双峰现象,表明地层形成时期为湿润气候,沉积动力多元化,遗址地貌发生了变迁,人类活动的强度较早期有明显减弱。     

国土资源信息专用标准规则研究

在综述国内外信息技术领域、地理信息领域专用标准进展和列举国土资源信息专用标准构成方式的基础上,对国土资源信息专用标准的制定规则进行研究,确定了国土资源信息专用标准的基础标准构成、专用标准与基础标准的关系、专用标准的一致性要求和一致性测试及专用标准的文档结构,提出了专用标准实施中需解决的问题.     

An experimental study of the water transfer through confined compacted GMZ bentonite

GMZ bentonite has been considered as a possible material for engineered barrier in the Chinese program of nuclear waste disposal at great depth. In the present work, the hydraulic conductivity of this bentonite was determined by simultaneous profile method. A specific infiltration cell equipped with five resistive relative humidity probes was designed for this purpose. The water retention properties were studied under both confined and unconfined conditions; the results show that at high suctions (> 4 MPa) the water retention capacity is independent of the confining condition, and by contrast, at low suctions (< 4 MPa) the confined condition resulted in significant low water retention. Furthermore, the microstructure was investigated at mercury intrusion porosimetry (MIP) and Environmental Scanning Electron Microscope (ESEM) in different states: on oven-dried powder, bentonite slurry, as-compacted and wetted samples. It has been observed that the soil powder is constituted of aggregates of various sizes; these aggregates are destroyed by full saturation at a water content equal to the liquid limit; compaction at the initial water content of 11–12% and a dry density of 1.7–1.75 Mg/m³ led to a microstructure characterized by a dense assembly of relatively well preserved aggregates; saturation of the compacted sample under constant volume condition defined a non-homogeneous microstructure with the presence of well preserved aggregates. This non-homogeneous microstructure would be due to the non uniform distribution of the generated swelling pressure within the soil sample upon wetting. The hydraulic conductivity determined has been found decreasing first and then increasing with suction decrease from the initial value of about 80 MPa to zero; the decrease can be attributed to the large pore clogging due to soft gel creation by exfoliation process, as observed at ESEM.     

简易纵剖面仪及其在岩体结构面粗糙度系数研究中的应用

本文介绍了自制简易纵剖面仪的基本原理、主要部件及其操作要点。简易纵剖面仪具有原理简单、设备轻便、操作简便、实用效果好且速度快等优点。用简易纵剖面仪可快速绘制大量结构面表面轮廓曲线,以便进行JRC统计分析和结构面抗剪强度的统计估算,克服了由于样本数少而估算结果代表性差的缺陷;还可以从统计角度研究结构面JRC和抗剪强度的尺寸效应、各质异性和各向异性等问题,为客观地综合评价岩体结构面抗剪强度提供可靠依据。文末根据实用效果指出简易纵剖面仪在工程实践中的广阔应用前景。     

风廓线与测风塔资料在地面风场预报中的应用研究

运用四维同化方法将风廓线雷达和测风塔资料应用到WRF模式中,通过对比资料同化前后模式对地面风场的预报效果可知,加入风廓线雷达和测风塔资料后模式对风速的预报效果有明显提高,对风向的预报也有一定程度的改善;资料同化结束后,模式预报在49h内对地面风场预报效果仍有明显改善,但随着模式预报时间的增加,在模式积分49h以后,同化资料前后模式对地面风场的预报效果无明显变化。另外,通过对资料同化前后模式对风速预报误差的分析可知,在对模式风场预报的改进中风廓线雷达资料的贡献大于测风塔资料的贡献。     

银川断陷盆地地壳结构与构造的地震学证据

通过跨银川断陷盆地,完成了一条长68.9 km的高分辨深地震反射探测剖面,首次获得了银川盆地地壳精细结构、地堑型断陷盆地深部断裂系（黄河断裂、银川断裂、贺兰山东麓断裂）特征及深浅构造关系.结果表明：银川断陷盆地上地壳为双程走时8 s（深度约20 km）反射面以上的区域,上地壳上部地层层位丰富,地层分段连续性较好,上地壳下部地层分层特征不明显,地质构造简单;下地壳(8～13 s)反射能量较弱,反射同相轴不明显;下地壳下部壳幔过渡带（13 s附近）由一组能量较强、持续时间较长（1.5 s）的反射波组组成,厚度约4.5 km.芦花台断裂、银川断裂分别于12～12.5 km、18～19 km深处交汇于贺兰山东麓断裂,贺兰山东麓断裂于28～29 km深处交汇于黄河断裂,黄河断裂为错断Moho面的深大断裂,银川地堑为以黄河断裂为主,其他断裂为辅组合而成的负花状构造.根据贺兰山东麓断裂和银川断裂的相互关系,认为贺兰山东麓断裂对1739年平罗—银川8级地震起主要控制作用.     

Identification of steps and pools from stream longitudinal profile data

Field research on step–pool channels has largely focused on the dimensions and sequence of steps and pools and how these features vary with slope, grain sizes and other governing variables. Measurements by different investigators are frequently compared, yet no means to identify steps and pools objectively have been used. Automated surveying instruments record the morphology of streams in unprecedented detail making it possible to objectively identify steps and pools, provided an appropriate classification procedure can be developed.To achieve objective identification of steps and pools from long profile survey data, we applied a series of scale-free geometric rules that include minimum step length (2.25% of bankfull width (W_b)), minimum pool length (10% of W_b), minimum residual depth (0.23% of W_b), minimum drop height (3.3% of W_b), and minimum step slope (10° greater than the mean slope). The rules perform as well as the mean response of 11 step–pool researchers who were asked to classify four long profiles, and the results correspond well with the channel morphologies identified during the field surveys from which the long profiles were generated. The method outperforms four other techniques that have been proposed. Sensitivity analysis shows that the method is most sensitive to the choice of minimum pool length and minimum drop height.Detailed bed scans of a step–pool channel created in a flume reveal that a single long profile with a fixed sampling interval poorly characterizes the steps and pools; five or more long profiles spread across the channel are required if a fixed sampling interval is used and the data suggest that survey points should be located more frequently than the diameter of the step-forming material. A single long profile collected by a surveyor who chooses breaks in slope and representative survey points was found to adequately characterize the mean bed profile.     

唐山震区深反射剖面分析

为了进一步研究唐山地区深部地壳构造与唐山大地震孕育及发生的关系,国家地震局地球物理研究所在石油部物探局的协助下,于1985年1月在唐山震区完成了64km长的深反射剖面野外观测,获得了高分辨率的整个地壳结构的详细资料。分析结果表明,唐山震区内深度500m以上的沉积层十分破碎;结晶基底为前震旦纪地层,埋深2—7km不等,覆盖地层倾斜,且断层发育,其中陡河断裂为正断层,延深至6—7km,推断该断层为1976年唐山发震的重要构造之一。测线上大约21km深处普遍存在一反射层;莫霍面深度在31—32km左右,与该地区折射剖面得到的结果相当一致。