Hysteresis‐based analysis of overland metal transport

Introducing a concept of equivalent mass depth of flow, this study describes the phenomenon of non‐point source pollutant (metal) transport for pavement (or overland) flow in analogy with wave propagation in wide open channels. Hysteretic and normal mass rating curves are developed for runoff rate and mass of 12 dissolved and particulate‐bound metal elements (pollutants) using the rainfall‐runoff and water quality data of the 15 × 20 m² instrumented pavement in Cincinnati, USA. Normal mass rating curves developed for easy computation of pollutant load are found to be of a form similar to Manning's, which is valid for open channel flows. Based on the hysteresis analysis, wave types for dissolution and mixing of particulate‐bound metals are identified. The analysis finds that the second‐order partial‐differential equation normally used for metal transport does not have the efficacy to describe fully the strong non‐linear phenomena such as is described for various metal elements by dynamic waves. In addition, the proportionality concept of the popular SCS‐CN concept is extended for determining the potential maximum metal mass M_p of all the 12 elements transported by a rain storm and related to the antecedent dry period (ADP). For the primary metal zinc element, M_p is found to increase with the ADP and vice versa. Copyright © 2003 John Wiley & Sons, Ltd.     

A Procedure for Determining the Reaction Curve of Shotcrete Lining Considering Transient Conditions

Summary The mechanical behaviour of a shotcrete lining is analysed in this paper using the convergence-confinement approach. A calculation procedure is presented which is able to provide the reaction curve of a lining with increasing stiffness, by taking into account the variability due to time of the shotcrete stiffness and strength, as well as the face advancement rate. The proposed procedure is also able to provide the change of the safety factor of the lining in time. This results to be a very useful tool for understanding the behaviour of this widely used support and for assigning its thickness to guarantee stability (also in transient conditions), with a known safety factor, during tunnel excavation. Received May 25, 2001; accepted July 18, 2002; Published online January 21, 2003 Acknowledgements The author would like to thank Prof. S. Pelizza and Dr. S. Xu for the help given during the preparation of this paper. The help of the Editor G. Barla is also acknowledged. Authors' address: Dr. P. P. Oreste, Department of Earth Resources and Land, Politecnics di Torino, corso Duca degli Abruzzi 24, 1-10129 Torino, Italy; e-mail: oreste@polito.it     

ADVANCES IN MEASURING TECHNIQUES OF BED LOAD

I.m~UCrIONBedloadisthesedimentwhichmovesalongtheriverbedintheformofrolling,slidingandsaltation.BedloadmaycreatemanyproblemsintheoperationandmaintenanceofnavigationchannelandinthedevelOPmentofhydroelectricity.Dataofbedloaddischargearealsorequiredinthedesignofreservoir,inwhichtheinflowbedloadareallactuallytrapped.Thewaysofbedloadmotionaredifferentfordifferentsizes.Thus,itisextremelydifficulttodeterminethebedloaddischargeaccurately.Manyequationshavebeenproposedtocalculatethebedloaddischarge.H…     

饱和软土压缩曲线的“反常”现象

饱和软土压缩试验时,经常出现压缩曲线“反常”、压缩系数“倒大”的现象。它是土的原始结构发生破坏前后的不同压缩性的客观反映。饱和软土的结构力很微弱,唯质量好的原状土才能见到这种“反常”。应从成孔、取样、测试及资料整理等多个环节保证其工程意义。     

Some observations of bipolar flashes during summer thunderstorms near Warsaw

Lightning discharges monitored by the SAFIR network system in Poland have been additionally identified over the 100×100 km area near Warsaw by single-point independent recordings of electric field and Maxwell current rapid changes. The data collected in summer thunderstorm days of 2002 showed some untypical properties of the lightning discharges which are rarely observed. Especially remarkable was a number of ground multi-stroke flashes with the return strokes (RS) which transported to the earth charges of opposite signs. Bipolar flashes (BF) of this kind were mostly involved in the events in which the nearby intracloud (ic) and cloud-to-ground (c-g) discharges were very closely associated in time. Events of such a close collocation of two different types of lightning discharges, previously called the complex lightning discharge events (CLDE), were quite often observed during summer thunderstorms in Poland. The events of this kind, i.e. 8 flashes, identified by the SAFIR detection system as BF’s present the multiple stroke flashes of the mean horizontal separation distance between striking points of particular RS equal to (2.8 ± 2.1) km and of the mean time interval between strokes of (46.8 ± 74.4) ms. The time separation between the observed BF and the adjacent ic flashes was from 0.1 to 335 ms, and horizontal separation distance between them ranged from 1.8 to 14.5 km. The multiplicity of the recorded BF’s ranged from 2 to 4 strokes. Four of these BF’s followed the ic discharge, but the other three preceded the ic and one was alone with no close ic.     

曲线拟合法对路基小变形情形适用性研究

双曲线法、三点法、指数曲线法和Asaoka法等曲线拟合法在软土路基的沉降预测中已经得到广泛应用,但在路基小变形情形的应用研究尚少。结合某铁路客运专线施工现场观测的路基小变形数据,对这4种方法,探讨了时间起点和样本值的起止时间间隔对相关系数的影响,且验算后期观测值的预测效果;并综合考虑了相关系数和相对误差,研究每种方法的适用性;指出了4种拟合方法在路基小变形情形应用的优缺点。研究表明：数据的波动会造成指数曲线法无法计算;沉降数据波动较小时,双曲线法、三点法、Asaoka法的拟合效果均较好;当沉降数据波动较大时,仅三点法、Asaoka法的拟合效果较好,双曲线法较差。     

冲绳海槽千年来陆源物质输入历史与东亚季风变迁

为解决近1000年以来东海沿岸地区气候演化及其对南冲绳海槽陆源物质输入的影响, 对取自南冲绳海槽的MD05-2908孔上部(0~810cm) 共78份孢粉样品和199份有机碳同位素样品进行了分析.结果显示, 近1000年以来南冲绳海槽陆源物质输入存在着显著波动, 其中1100~1040aBP、960~880aBP和800~480aBP期间, 陆源物质输入比例增加; 1040~960aBP和480~230aBP期间, 陆源物质输入比例减少.将陆源物质输入指标与陕西佛爷洞δ13C含量记录对比分析, 发现陆源物质输入比例变化与季风的变化密切相关.当夏季风减弱时, 导致降雨带长时间集中在南部地区, 增强的降雨量提高了风化剥蚀以及沉积物向海洋搬运的能力, 使得陆源物质供应量增加.      

均质边坡稳定性极限曲线法

基于滑移线场理论,按边坡坡面变形量评价其稳定性,提出均质边坡极限曲线法。该法是求有重边坡极限荷载的逆过程,也是强度折减法的对偶过程。以特征线法差分方程组（SCM）和试验方程近似公式（CCM）求得的极限坡面曲线与坡面线相交为变形破坏准则,定义了安全度（DOS）和破坏度（DOF）2个评价指标。该方法不必假设和搜索临界滑动面。经典考题和典型算例的验算表明,随着节点的增加SCM法计算精度增加,边界步长不变时,3次样条插值求得的变形破坏准则判断值不变,说明SCM算法稳定。典型算例的计算数据和图例表明,边坡角变大时边坡稳定性降低,极限坡面曲线与坡面由无交点变为有交点,证明了变形破坏准则的正确性。由2个例题计算结果对比可知,安全系数较大时,SCM法、CCM法计算结果与其具有可比性,相对于原边界条件增加了外荷载;安全系数变小时,SCM法、CCM法偏于保守。34个样本计算正确率为安全系数法67.7%,应力状态法73.5%,CCM法79.4%,SCM法70.6%,表明SCM法和CCM法正确率较高,计算结果可靠,SCM法、CCM法因素敏感性分析结论与安全系数法完全一致。在露天矿边坡稳定性和最终边坡角的分析与计算中,SCM法、CCM法结论与原报告相同,当参数变小时CCM法更有利于实践,具有一定的工程应用价值。     

长白山地区火山碎屑粒度特征研究

长白山地区全新世火山活动活跃,发育了良好的火山空降、火山碎屑流、火山涌流和火山泥石流堆积物。这些堆积物交错堆积,野外区分较为困难。在火山碎屑地层剖面调查基础上,系统采集了各种类型的火山碎屑堆积物样品。在实验室通过粒度参数和概率累积曲线分析,对堆积物成因类型进行了判别,讨论了火山空降堆积物和火山碎屑流堆积物随着与火口距离变化的规律。首次对研究区内粒度范围为62.5～0.02μm的细火山灰进行了粒度分析,对火山碎屑流和火山碎屑涌流中细火山灰端元分布特征和地质意义进行了分析和讨论     

CX盆地露头岩样电阻率测试与分析

本次实验的主要目的是对ＣＸ地区露头完好的岩样进行电阻率测试,提出了一种利用露头岩样电阻率绘制模拟地层条件下仿真电阻率测井曲线的新方法。该方法的主要思路是：（１）在ＣＸ地区选取一条露头出露较完好的地质剖面,在野外进行详细的岩性、地层产状和厚度描述,并采集露头岩石标本。（２）对所取岩样进行常温常压下的密度、孔隙度和电阻率测试,并选部分代表一定岩性的岩样进行模拟地层环境（压力、饱和度、孔隙度）下的电阻率