Rock-avalanche dynamics: insights from granular physics experiments   总被引：1，自引：0，他引：1  

S. Julio Friedmann  N. Taberlet  W. Losert 《International Journal of Earth Sciences》2006,95(5):911-919

Rock avalanches are known to behave in extraordinary ways unlike other landslides, and their deposits in part reflect their unusual physical behavior. Recent experiments in granular physics suggest that many phenomena and features simply reflect the non-linear nature of granular flows, although some behavior cannot simply be reproduced in lab scale experiments. In a static configuration, grain–grain contact networks dominate the distribution of forces and stresses within a granular mass. During flow, granular collisions damp the system through energy dissipation, while gravitational potential drives the system. The energy distribution between static and collisional stresses within the system can change very rapidly. Threshold events dominate system response, and the challenge is to find which characterization of the static phase helps to predict failure (and thus flow) resistance. Once flowing, many “unusual” rock-avalanche phenomena are entirely consistent with the physics of flow of large granular masses, but the low energy dissipation rate required for long run-out events requires the presence of physical processes that are not involved in experimental flows in the current parameter range or in the assumptions of current models.  相似文献   

Impact of rehabilitation of Assiut barrage, Nile River, on groundwater rise in urban areas   总被引：1，自引：0，他引：1  

Mohamed A. Dawoud  Nahed E. El Arabi  Ahmed R. Khater  Jan van Wonderen 《Journal of African Earth Sciences》2006,45(4-5):395-407

To make optimum use of the most vital natural resource of Egypt, the River Nile water, a number of regulating structures (in the form of dams and barrages) for control and diversion of the river flow have been constructed in this river since the start of the 20th century. One of these barrages is the Assiut barrage which will require considerable repairs in the near future. The design of the rehabilitation of the barrage includes a headpond with water levels maintained at a level approximately 0.60 m higher than the highest water level in the headpond of the present barrage. This development will cause an increase of the seepage flow from the river towards the adjacent agricultural lands, Assiut Town and villages. The increased head pond level might cause a rise of the groundwater levels and impedance of drainage outflows. The drainage conditions may therefore be adversely affected in the so-called impacted areas which comprise floodplains on both sides of the Nile for about 70 km upstream of the future barrage. A rise in the groundwater table, particularly when high river levels impede drainage, may result in waterlogging and secondary salinization of the soil profile in agricultural areas and increase of groundwater into cellars beneath buildings in the urban areas. In addition, a rise in the groundwater table could have negative impact on existing sanitation facilities, in particular in the areas which are served with septic tanks. The impacts of increasing the headpond level were assessed using a three-dimensional groundwater model. The mechanisms of interactions between the Nile River and the underlying Quaternary aquifer system as they affect the recharge/discharge processes are comprehensively outlined. The model has been calibrated for steady state and transient conditions against historical data from observation wells. The mitigation measures for the groundwater rise in the urban areas have been tested using the calibrated mode.  相似文献   

位场正则化下延在自然电位概率成像中的应用     

阮帅  王绪本  高永才  毛利峰 《物探化探计算技术》2006,28(4):332-336

通过位场正则化向下延拓方法,弥补自然电位法对于地下全空间信息反映不足的客观缺陷,改进仅通过地表数据成像而导致的深度不灵敏状况。在模型分析中,新方案的成像结果和真实模型非常吻合。对于实测资料解释,新方案的处理结果在横向上符合实测数据的异常反映,同时还能够准确的给出地下半空间的纵向信息。  相似文献   

分布式变频调节管网系统的方案比较分析     

徐楠  王树刚 《中国勘察设计》2006,(5):46-48

随着变频枝术的发展，流体输配管网中用户分支用变频泵代替调节阀的分布式变频调节系统越来越受到关注。通过与传统设计方案相比，本文定量分析了分布式变频调节系统运行节能的原因和不同调节方式的节能差异。在所给的算例中，考虑了十种方案，包括传统设计方案、四种分布式非混水变频调节方案和五种分布式混水变频调节方案。对于非混水变频调节方案和分布式混水变频调节方案两个类型中，区别是在用户分支是否安装了变频泵。随着变频泵的增多，主循环水泵的扬程逐渐变小。用户变频泵的扬程也随着混水和非混水系统的不同，而呈现不同的变化规律。  相似文献   

Hydrogen from coal: Production and utilisation technologies   总被引：2，自引：0，他引：2  

E. Shoko  B. McLellan  A.L. Dicks  J.C. Diniz da Costa   《International Journal of Coal Geology》2006,65(3-4):213-222

Although coal may be viewed as a dirty fuel due to its high greenhouse emissions when combusted, a strong case can be made for coal to be a major world source of clean H₂ energy. Apart from the fact that resources of coal will outlast oil and natural gas by centuries, there is a shift towards developing environmentally benign coal technologies, which can lead to high energy conversion efficiencies and low air pollution emissions as compared to conventional coal fired power generation plant. There are currently several world research and industrial development projects in the areas of Integrated Gasification Combined Cycles (IGCC) and Integrated Gasification Fuel Cell (IGFC) systems. In such systems, there is a need to integrate complex unit operations including gasifiers, gas separation and cleaning units, water gas shift reactors, turbines, heat exchangers, steam generators and fuel cells. IGFC systems tested in the USA, Europe and Japan employing gasifiers (Texaco, Lurgi and Eagle) and fuel cells have resulted in energy conversions at efficiency of 47.5% (HHV) which is much higher than the 30–35% efficiency of conventional coal fired power generation. Solid oxide fuel cells (SOFC) and molten carbonate fuel cells (MCFC) are the front runners in energy production from coal gases. These fuel cells can operate at high temperatures and are robust to gas poisoning impurities. IGCC and IGFC technologies are expensive and currently economically uncompetitive as compared to established and mature power generation technology. However, further efficiency and technology improvements coupled with world pressures on limitation of greenhouse gases and other gaseous pollutants could make IGCC/IGFC technically and economically viable for hydrogen production and utilisation in clean and environmentally benign energy systems.  相似文献   

A test of the Tate equation to predict bubble size at an orifice in the presence of frother     

Jose R. Hernandez-Aguilar  Ryan CunninghamJames A. Finch 《International Journal of Mineral Processing》2006

Air bubbles of uniform size (ca. 1 mm diameter) were generated at a submerged orifice (glass capillary) under controlled frequency (down to ca. 0.06 s^− 1) in aqueous solutions of frother (Dowfroth 250). The bubbles were sized with an imaging technique. One objective was to establish whether the Tate equation (static balance between buoyancy and capillary forces) could be used as a standard sizing calibration method. Another aim was to verify whether with decreasing surface tension (due to increasing frother concentration) the anticipated decrease in bubble size agreed with the equation prediction. An effect of frother was detected compatible with the role of surface tension but divided into two concentration regions, seemingly the result of a gradual change in bubble shape and wetting: > 6 ppm the bubble holds a spherical shape and the capillary appeared to be completely wetted while at ≤ 6 ppm a degree of non-wetting and bubble distortion (neck formation just prior to detachment) were apparent, supported by qualitative observations. In addition, at > 6 ppm the Tate value was only approached by decreasing the bubble frequency but not attained. Plausible causes for the failure to reach the predicted size are discussed.  相似文献   

Generic precursors to coastal earthquakes: Inferences from Denali fault earthquake   总被引：2，自引：0，他引：2  

Ramesh P. Singh  Guido Cervone  Vijay P. Singh  Menas Kafatos 《Tectonophysics》2007,431(1-4):231

Recent research has shown evidence of strong coupling between the atmosphere and lithosphere in coastal regions, associating abnormal atmospheric phenomena to the occurrence of strong earthquakes. Surface latent heat flux (SLHF), total column water vapor (CWV), relative humidity (RH) and total ozone column (TOC), analyzed over the epicentral region of the Denali fault earthquake of November 3, 2002, exhibit anomalous behavior that could be related to the earthquake preparatory process and its occurrence. The complementary nature of the parameters provides strong support that the anomalous values were driven by lithospheric processes, rather than other atmospheric phenomena. Due to the wide availability of remote sensing observations of atmospheric parameters, the detection of anomalies can be used to mitigate the earthquake risks.  相似文献   

Modeling surface roughness degradation of rock joint wall during monotonic and cyclic shearing   总被引：2，自引：0，他引：2  

Tikou Belem  Mountaka Souley  Françoise Homand 《Acta Geotechnica》2007,2(4):227-248

  相似文献   

A GIS-based methodology for hazard mapping of small volume pyroclastic density currents     

G. P. Toyos  P. D. Cole  A. Felpeto  J. Martí 《Natural Hazards》2007,41(1):99-112

We present here a methodology implemented within a geographical information system (GIS) for hazard mapping of small volume pyroclastic density currents (PDCs). This technique is implemented as a set of macros written in Visual Basic for Applications (VBA) that run within GIS-software (i.e. ArcGIS). Based on the energy line concept, we calibrated an equation that relates the volume (V) and the mobility (ΔH/L) of single PDCs using data from Soufrière Hills volcano (Montserrat) and Arenal volcano (Costa Rica). Maximum potential run-outs can be predicted with an associated uncertainty of about 30%. Also based on the energy line concept and with data from Soufrière Hills volcano and Mt. St. Helens (USA), we were able to calibrate an equation that predicts the flow velocity as a function of the vertical distance between the energy line and the ground surface (Δh). Velocities derived in this way have an associated uncertainty of 3 m s⁻¹. We wrote code to implement these equations and allow the automatic mapping of run-out and velocity with the inputs being (i) the height and location of the vent (ii) the flow volume and (iii) a digital elevation model (DEM) of the volcano. Dynamic pressure can also be estimated and mapped by incorporating the density of the pyroclastic density current (PDC). This computer application allows the incorporation of uncertainties in the location of the vent and of statistical uncertainties expressed by the 95% confidence limits of the regression model. We were able to verify predictions by the proposed methodology with data from Unzen volcano (Japan) and Mayon volcano (The Philippines). The consistencies observed highlight the applicability of this approach for hazard mitigation and real-time emergency management.  相似文献   

Making space for unruly water: Sustainable drainage systems and the disciplining of surface runoff     

Phil Jones  Neil Macdonald 《Geoforum》2007,38(3):534-544

This paper explores the disciplining of non-human actors through the example of sustainable drainage systems (SuDS) managing surface water runoff. The lens of performativity is used to examine the move from pre-modern repressive forms of discipline, to mechanisms which attempt a more productive disciplinary engagement by finding space to reform water’s more unruly behaviours. After examining the problems with traditional disciplinary approaches to water of rapid transit and exile, the paper explores the implications of a move towards SuDS technology. This change is examined using a case study of Glasgow, Scotland, where there is an attempt to utilise less repressive disciplinary mechanisms and to find spaces in the city for surface water outside the hard drainage infrastructure. New approaches to the disciplining of urban water are conceptualised as being a performance of tension between water and those who would modify its behaviour.  相似文献