Rock resistance to erosion: Some further considerations     

Paul C. Augustinus 《地球表面变化过程与地形》1991,16(6):563-569

Rock resistance to erosion is an often described factor in geomorphic studies, and is generally considered to strongly influence the shape of erosional landforms. However, the property of the rock mass that enables it to resist erosion is rarely considered, and its measurement is rarely justified and assessed adequately. Allison (1988, 1990) examined the intact strength properties of several types of carbonate rocks and considered that dynamic Young's modulus is a good indicator of rock material strength for geomorphic purposes, and cast doubts on the reliability of Schmidt hammer tests for this purpose. Alternative approaches to rock characterization from the view point of evaluating rock intact strength are considered.  相似文献   

Time-dependency of runoff velocity and erosion the effect of the initial soil moisture profile   总被引：1，自引：0，他引：1  

Gerard Govers 《地球表面变化过程与地形》1991,16(8):713-729

The paper reports on experiments carried out to evaluate the effect of the initial soil moisture profile on temporal variations in runoff erosion rate. The moisture profile was varied by applying infrared heating to the soil sample surface over various time periods, while runoff erosivity was varied by varying the slope of the flume. The experiment confirms that dry loamy soils are very erodible: on a slope length of only 4.3 m long sediment concentrations are near transporting capacity in case of a dry soil sample. It appears that temporal variations in sediment concentrations can be well simulated using a simple relationship between runoff erosion resistance and initial soil moisture content, thereby implicitly assuming that the effect of initial moisture content is persistent over the whole duration of the experiment. The implications of these findings with respect to the modelling of sediment output from larger catchments and the design of experiments on rill erodibility are discussed. The experiments also show that, under the present circumstances, mean velocities in the rills appear to be independent of slope. This finding may be of importance with respect to overland flow routing and deterministic erosion modelling.  相似文献   

On the stability of the geostatistical method     

Noel Cressie  Dale L. Zimmerman 《Mathematical Geology》1992,24(1):45-59

A thorough geostatistical analysis of spatial data, observed at given spatial locations, includes exploratory data analysis, spatial-model building, diagnosing the model fit, and inference on unknown model parameters or unobserved values (at known locations). Using results from mathematical analysis, exact and asymptotic distribution theory, and simulation studies, we argue that, when used sensibly, the geostatistical method is reassuringly stable.  相似文献   

通风参数计算的灰色建模法     

张国屏  赵云胜 《地球科学》1988,(4)

本文根据灰色建模理论,提出灰色模型群建模法。其实质是利用计算机,对一系列预报模型进行比较,输出了个最优模型。文中通风管流参数计算的灰色建模结果令人满意,说明灰色建模理论在实验数据处理中是一个有力工具。  相似文献   

Resistance to flow past deformable boundaries     

T. R. Davies  A. J. Sutherland 《地球表面变化过程与地形》1980,5(2):175-179

An hypothesis from which a general principle covering deformation of alluvial boundaries may be developed is proposed, namely—flow of fluid past a deformable boundary will deform the boundary so as to increase the resistance to flow. Upon attainment of a local maximum of resistance to flow the boundary shape will cease to change. Evidence from channel bed forms, meander geometry and armoured beds is presented to support the hypothesis. One implication of the hypothesis is that channels will adjust so that sediment movement is maximized. The authors would like geomorphologists to test this in their work on landscape evolution.  相似文献   

Characteristics of multiple-fan ventilation networks   总被引：1，自引：0，他引：1  

Y. J. Wang 《Geotechnical and Geological Engineering》1984,2(3):229-243

Summary The definitions of system pressure loss (mine head) and system resistance, which are traditionally associated with single-fan networks, are applied to multiple-fan ventilation networks. The system characteristics, relations among air power, pressure loss, air quantity and resistance, are analysed by introducing the concept of subsystems. These subsystems are associated with the fans located in a cutset of the network.For a multiple-fan network, the resistances for the subsystems and total system are dependent on the quantity ratios of the subsystems. In general the pressure loss of a subsystem or a total system does not vary as the square of the corresponding air quantity. If the quantity ratios of subsystems are all held constant, then the resistances become constant and the pressure losses are predictable from the quantities employing the square law. The system resistance has a minimum value under the natural-splitting flow pattern. Being independent of the value of system quantity, the minimum system resistance provides a basis for comparing the different networks.  相似文献   

山区卵砾石河道水流阻力计算          下载免费PDF全文

罗铭  黄尔  王协康  杨奉广 《水科学进展》2020,31(3):404-412

卵砾石河道广泛存在于山区河流中,在卵砾石河床近底层的水流流速低于上方流速,速度剖面出现拐点,类似于自由剪切流动,传统的指数型和对数型水流阻力公式计算误差偏大。将自由剪切流理论类比到山区卵砾石河道,并考虑山区河流特殊流态、流场和剪切力的影响,引入雷诺数(Re)、弗劳德数(Fr)和摩阻流速利用水槽数据进一步修正了该类水流阻力公式。筛选位于意大利南部的亚平宁山脉140条山区河流野外数据对新公式进行验证,并检验对比了已发表的多个山区河流阻力公式。结果表明:修正后的水流阻力公式Nash-Sutcliffe效率指数最接近1、均方根误差最小、相对误差最小。自由剪切流动的类比是从湍流结构角度推导河道水流阻力,能更好地阐释特殊水流结构,进而提高计算精度。  相似文献   

唐山抗震精神的形成和历史意义     

李贵  宗玉田 《国际地震动态》1996,(12):23-28

文章以丰富的第一手资料为依据，深刻地揭示唐山抗震精神产生的根源，提出中华民族的传统文化是抗震精神的直接思想来源，近代工业革命锤炼的唐山人是抗震精神的主体，伟大的抗震减灾斗争是抗震精神的实践基础，以此为基础，阐述了唐山抗震精神在抗震减灾中的作用历史意义。  相似文献   

农田N_2O通量测定方法分析   总被引：3，自引：0，他引：3  

李俊  于沪宁  于强  谢贤群 《地学前缘》2002,9(2):377-385

采用空气动力学方法、波文比 /能量平衡法及密闭箱法结合气相色谱分析对农田N2 O通量进行了测定。在夏天和秋天观测前的 1～ 2周 ,148和 10 9kgNhm-2 肥料被分别施入夏玉米田和冬小麦田。实验表明 :空气动力学法与波文比 /能量平衡法测定的N2 O通量在冬小麦田较为接近 ,在夏玉米田则相差较大。夏玉米冠层上方温湿梯度的细微变化可导致能量平衡法计算的N2 O通量发生较大离散 ,从而与空气动力学法的计算结果产生较大偏差。观测期间 ,微气象法和密闭箱法测定的农田N2 O日平均通量在夏玉米田分别为 18± 37和 8± 5ngNm-2 ·s-1;在冬小麦田分别为 43± 2 1和 6± 1ngNm-2 ·s-1。微气象法测定的农田N2 O通量高于密闭箱法的观测值 ,由此推测作物冠层可释放N2O ,其机制可能是土壤中生成的N2 O被作物的蒸腾液流输送到大气中。微气象法和密闭箱法测定的N2 O通量间的差异在冬小麦田大于夏玉米田 ,表明冬小麦释放N2 O的量大于夏玉米。这可能是冬小麦根系分布较夏玉米深的缘故。采用密闭箱法观测时 ,箱内气温发生变化 ,半小时内最高可增加10℃ ,因地温变化小 ,其对土壤中N2 O的生成并无显著影响。由于密闭箱法观测忽略或低估了植物释放的N2 O ,且箱内的边界层阻力可能高于箱外 ,其测定的地表N2 O通量偏小。  相似文献   

地震作用与风荷载的组合问题   总被引：1，自引：0，他引：1  

常宝琦  梁纪彬 《华南地震》1997,17(3):48-53

选择广州和汕头作为广东沿海地抠的典型城市，用极Ⅰ型和极值型统计了两是风压和地艇（烈度）资料，然后用弗里博斯－卡斯坦尼塔载过程模型给出两市的风荷载和地震作用的组合系数。最后利用广州市广东国际大厦和汕头市国际大酒店的抗震、抗风险算结果，作了进一步的讨论。  相似文献