A hybrid method for size characterization of coarse subsurface fluvial sediments     

Stephen P. Rice  Judith K. Haschenburger 《地球表面变化过程与地形》2004,29(3):373-389

This paper introduces and evaluates a novel method for ascertaining the grain‐size distribution of subsurface sediments that involves profoundly less sampling effort than standard methods. It is based on hybrid sampling principles previously applied to the construction of synthetic surface grain‐size distributions. The method is developed from an empirical demonstration of the approximate similarity of surface and subsurface grain‐size distributions when compared over a common range of sizes. Subsurface hybrid models are found to provide good facsimiles of grain‐size distributions de?ned using standard criteria and to yield distribution percentiles with millimetre accuracy. The technique is presented as an expedient alternative to standard methods for large, perennial gravel‐bed rivers. As this is a new technique, prudent application is advised in lieu of further investigation. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Comparison of hydraulic geometry between sand‐ and gravel‐bed rivers in relation to channel pattern discrimination     

Jiongxin Xu 《地球表面变化过程与地形》2004,29(5):645-657

A comparison has been made between the hydraulic geometry of sand‐ and gravel‐bed rivers, based on data from alluvial rivers around the world. The results indicate a signi?cant difference in hydraulic geometry among sand‐ and gravel‐bed rivers with different channel patterns. On this basis, some diagrams for discrimination of meandering and braided channel patterns have been established. The relationships between channel width and water discharge, between channel depth and water discharge, between width–depth ratio and water discharge and between channel slope and water discharge can all be used for channel pattern discrimination. The relationship between channel width and channel depth can also be used for channel pattern discrimination. However, the accuracy of these relationships for channel pattern discrimination varies, and the depth–discharge relationship is a better discriminator of pattern type than the classic slope–discharge function. The cause for this difference has been explained qualitatively. To predict the development of channel patterns under different natural conditions, the pattern discriminator should be searched on the basis of independent or at least semi‐independent variables. The relationship between stream power and bed material grain size can be used to discriminate channel patterns, which shows a better result than the discriminator using the slope–discharge relationship. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

塔河油田卡拉沙依组砂组沉积相与储层研究     

樊怀阳  陈文  刘百春 《新疆地质》2004,22(4):417-421

卡拉沙依组砂岩是塔河油田石炭系重要储层，从上到下分为4个砂组，即Ⅰ砂组、Ⅱ砂组、Ⅲ砂组及Ⅳ砂组，根据岩石组合特征、岩石粒度、分选性、以及沉积构造等特征，可得出Ⅰ砂组为较典型的扇三角洲沉积环境；Ⅱ-Ⅳ砂组为潮坪环境，其中Ⅲ砂组沉积时的古环境水动力相对最强，以潮间带下部为主，储层砂体最发育，单个砂体的厚度也最大，为纵向上最好储层段。  相似文献   

曲线铁路路基下沉病害检测与分析     

杨新安  陈春安  温国春 《岩土力学》2004,25(9):1397-1400

以阐明曲线铁路路基下沉病害检测、基床强度评估和病害成因分析方法为目标，采用轻便动力触探试验和土工试验方法对沪宁线下行k55 450-k55 500曲线路基下沉病害段进行了试验测试，根据轻便动力触探和土工试验结果，计算出曲线路基基床承载力，与曲线线路路基中总应力进行比较，评估了基床强度状况，分析出该段曲线铁路路基病害产生的成因。  相似文献   

岩层移动动态过程的离散单元法分析   总被引：2，自引：0，他引：2  

张建全  于友江 《水文地质工程地质》2004,31(2):9-13

采动覆岩动态发展过程受地质、采矿条件诸多因素的影响,是一个十分复杂的时空过程。通过离散单元法数值模拟,揭示了综放开采条件下采场上覆岩层动态发展规律,特别是覆岩离层缝隙的分布规律、发展形态、空间位置以及与地质采矿条件的关系,揭示了工作面推进过程中,采场上覆岩层中重新分布的应力大小、方向及其发展变化规律,该应力的存在和变化规律是确定井下开采方法、支护方式的依据。  相似文献   

    

Roberto Torra 《中国地球化学学报》2004,23(3):220-237

Littoral siliciclastic shallow marine horizontal conformable beds (a heterolithic succession), Middle to Late Miocene, outcropping in northeastern Argentina (Ituzaingó Formation) and overlying transitional conformable horizontal regolithic mantle-rock bed derived from them (the Pampean and Post-Pampean Formations), were geochemically analyzed. The focus of this study is placed on the application of geochemical parameter and signature analyses related with the aforementioned geological units, which are of subcontinental extension into South America. The encountered results show an outstandingly similar geochemical behaviour between them. The main conclusion is that regolithic mantle-rock beds were derived from the littoral shallow marine mudstone (silty-argillaceous) beds. This is in oposition to previous aeolian processes proposed early in the 50’s and later. These mudstone beds constitute important sections of the littoral shallow marine sequence beds (outcropping HST parasequence). Such regolitization proposed for the Pampean and Post-Pampean Formations predominantly developed in-situ during the Late Pleistocene and Holocene. The main erosional and mobilized agents were the surface free water (pluvial, fluvial and laminar water sheets) and vadose water. So, the wind flows and/or the immense air flow hurricanes are of insignificant sedimentological influence. Otherwise, there is not a proved appropiate sandy-silty reservoir for a reasonable support of the “aeolian hypothesis”, as well as clear aeolian structures settled in the regolithic mantle-rock bed. In spite of these lines of equality textural-structural evidence, the geochemical values for both major elements and trace elements, demonstrate that the Miocene heterolithic marine succession was the mother rock of the overlying regolithic mantle-rock bed, which was formed as an in-situ mantle-rock bed.  相似文献   

Beds comprising debrite sandwiched within co-genetic turbidite: origin and widespread occurrence in distal depositional environments   总被引：11，自引：0，他引：11  

P. J. Talling  L. A. Amy†  R. B. Wynn‡  J. Peakall†  M. Robinson 《Sedimentology》2004,51(1):163-194

Co‐genetic debrite–turbidite beds occur in a variety of modern and ancient turbidite systems. Their basic character is distinctive. An ungraded muddy sandstone interval is encased within mud‐poor graded sandstone, siltstone and mudstone. The muddy sandstone interval preserves evidence of en masse deposition and is thus termed a debrite. The mud‐poor sandstone, siltstone and mudstone show features indicating progressive layer‐by‐layer deposition and are thus called a turbidite. Palaeocurrent indicators, ubiquitous stratigraphic association and the position of hemipelagic intervals demonstrate that debrite and enclosing turbidite originate in the same event. Detailed field observations are presented for co‐genetic debrite–turbidite beds in three widespread sequences of variable age: the Miocene Marnoso Arenacea Formation in the Italian Apennines; the Silurian Aberystwyth Grits in Wales; and Quaternary deposits of the Agadir Basin, offshore Morocco. Deposition of these sequences occurred in similar unchannellized basin‐plain settings. Co‐genetic debrite–turbidite beds were deposited from longitudinally segregated flow events, comprising both debris flow and forerunning turbidity current. It is most likely that the debris flow was generated by relatively shallow (few tens of centimetres) erosion of mud‐rich sea‐floor sediment. Changes in the settling behaviour of sand grains from a muddy fluid as flows decelerated may also have contributed to debrite deposition. The association with distal settings results from the ubiquitous presence of muddy deposits in such locations, which may be eroded and disaggregated to form a cohesive debris flow. Debrite intervals may be extensive (> 26 × 10 km in the Marnoso Arenacea Formation) and are not restricted to basin margins. Such long debris flow run‐out on low‐gradient sea floor (< 0·1°) may simply be due to low yield strength (? 50 Pa) of the debris–water mixture. This study emphasizes that multiple flow types, and transformations between flow types, can occur within the distal parts of submarine flow events.  相似文献   

正交法在注浆材料优化设计中的应用          下载免费PDF全文

杨秀竹王星华  雷金山 《探矿工程》2004,31(3):7-9

应用正交试验设计法，对粘土固化浆液的配比进行了优化，得到了最佳配比，并将其应用于洛湛铁路益娄段岩溶路基的注浆加固，收到了很好的整治效果。  相似文献   

Channel Bed Mobility Downstream from the Elwha Dams,Washington*     

Molly Pohl 《The Professional geographer》2004,56(3):422-431

Dams are a major source of fragmentation and degradation of rivers. Although substantial research has been conducted on the environmental impacts of large structures in the United States, smaller dams have received less attention. This study evaluated the impact of two dams of moderate size, the Elwha Dams, on the downstream channel system using field data collection at river cross‐sections. The relationship of average boundary shear stress (τ_o) to critical shear stress (τ_cr) served as the basis for determining channel bed material mobility under the two‐year and ten‐year flood events. The channel had the greatest channel bed mobility at the natural cross‐section upstream from the dams, low bed mobility between the structures, and an increase in channel bed mobility in the low gradient river segment near the mouth of the river. Low bed mobility tended to be associated with a lack of channel system complexity, including reduction or loss of bars and low alluvial terraces and their associated young riparian communities. Although these run‐of‐the‐river dams do not modify streamflow greatly, the loss of sediment from the channel system has had a substantial impact on bed mobility and geomorphic and biotic complexity of the Elwha River.  相似文献   

The effect of bed mobility on resistance to overland flow     

Shixiong Hu  Athol D. Abrahams 《地球表面变化过程与地形》2005,30(11):1461-1470

When sediment grains are transported as bed load in overland flow, there is a net transfer of momentum from the flow to the grains. When these grains collide with other grains, whether on the bed or in the flow, streamwise flow velocity decreases and resistance to flow increases. Resistance to flow generated in this manner is termed bed‐load transport resistance. Resistance to flow f over a plane bed may be partitioned into grain resistance f_g and bed‐load transport resistance f_bt. We use the symbols f_btf and f_btm to denote f_bt for flows over fixed beds and over mobile beds, respectively, and we compute the effect of bed mobility on flow resistance f_mob by subtracting f_btf from f_btm. The data for this study come from 54 flume experiments with fixed beds and 38 with mobile beds. On average f_mob is approximately equal to half of f_btm, which is about one‐quarter of f. Hence, f_mob is about one‐tenth of f. Predictive equations are developed for f_btf, f_btm and f_mob using dimensional analysis to identify the relevant independent variables and regression analysis to evaluate the coefficients associated with these variables. Values of f_mob are always positive which implies that mobile beds offer greater resistance to flow than do fixed beds. Evidently bed‐load grains colliding with mobile beds lose more momentum to the bed than do grains colliding with fixed beds. In other words, grain collisions with mobile beds are less elastic than those with fixed beds. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献