Hydro-thermal performance of multilayer capillary barriers in arid lands     

A. M. O. Mohamed  I. Shooshpasha 《Geotechnical and Geological Engineering》2004,22(1):19-42

In this study, a capillary barrier system was designed and tested for an arid land environment. To simulate arid land conditions of high temperature and sub-irrigation systems, the barrier was subjected to thermal and hydraulic gradients in opposite directions; to test the barrier system under these severe conditions, an experimental apparatus was designed and fabricated. The multilayer capillary barrier consisted of three layers made of silica sand, a mixture of sand and bentonite in equal portions, and a mixture of clay (25%) and aggregate (75%). Several one dimensional coupled heat and moisture tests were performed. Temperature variations along the thickness of the barrier were recorded as a function of time, and at the end of each test, the barrier was sliced into small sections, for the determination of volumetric water content as a function of distance from the heat source. The experimental results were discussed in view of the barrier's intended purpose of its ability to store moisture for long time durations. Coupled heat and moisture flow equations were developed and solved numerically via a finite difference method. Diffusivity parameters were calculated by using experimental results, a numerical model, and Powell's conjugate directions method of nonlinear optimization. The model was calibrated and the results were discussed. Good agreement between calculated and experimental results was obtained. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

温州世贸中心大厦钻孔灌注桩施工技术          下载免费PDF全文

詹龙和  金克柏  谢秋明 《探矿工程》2004,31(10):1-3

介绍了温州世贸中心大厦钻孔灌注桩的主要特点和施工难点，以及在生产施工中所采取的主要技术措施，特别针对该工程中风化残留体施工难度大、桩孔深的特点，介绍了相应的处理办法和注意事项。  相似文献   

GPS广播星历参数拟合算法   总被引：25，自引：2，他引：25  

崔先强焦文海  贾小林尹豫疆 《测绘学院学报》2004,21(4):244-246

介绍了GPS广播星历参数的最小二乘估计方法。推导了相应的计算公式。计算结果表明。文中给出的公式是正确的，其拟合精度以用户距离误差(URE)示时，对预报轨道的损失小于1cm。  相似文献   

郑州强对流天气成因分析   总被引：1，自引：0，他引：1  

赵培娟 吴蓁郑世林  席世平 《河南气象》2005,(4):11-13

对2004年郑州出现的7次强对流天气过程的天气形势、影响系统及稳定度的分析结果表明：华北低涡和NW气流形势下存在着低层升温、高层降温机制,使大气层结趋于不稳定,当测站高低空温差或温度平流差达到一定量值,且近地层存在辐合系统时,易出现强对流; SW气流或高压控制时,大气高温高湿,具有较强不稳定能量,若850 hPa或地面出现辐合系统时,易产生强对流;地面湿度连续数天加大或保持在某一值域,其上空温湿24 h变化呈上趋冷下趋暖或上趋干下趋湿并达到一定量值,预示强对流的发生;700～500 hPa湿度明显减小,24 h温度露点差加大4 ℃以上,或近地层θse≥350K,中低层Δθse≥26 K,θse小值位于700 hPa或500 hPa,其厚度≥2000 m,易出现强雷雨大风; 700 hPa以下t-td≤4.3 ℃,或连续4天850 hPa t-td≤7 ℃、700 hPa t-td≤5 ℃、500 hPa t-td≤9 ℃,PW≥12,可预示短时暴雨的出现.  相似文献   

内蒙古中西部地区震源参数和场地响应反演   总被引：15，自引：0，他引：15       下载免费PDF全文

高立新  郑斯华  丁风和 《地震工程学报》2005,27(2):109-114

采用Atkinson方法，基于遗传算法，利用呼和浩特数字地震台网7个子台记录的9次质量较高的地震事件资料，计算了内蒙古中西部地区的品质因子Q值和非弹性衰减系数c（f）。在所研究的频率范围内，前者和频率．厂有很好的线形关系：Q（f）=116．8f^1.000后者与频率．厂的变化关系不明显。在此基础上采用Moya方法反演了7个地震台的场地响应和地震的震源参数，并对它们之间的相互关系进行了讨论。结果显示在所研究的频率域内7个基岩台站的场地均不同程度的存在放大作用，其次震源参数间具有较好的线性关系。本文还详细介绍了Atkinson方法和Moya方法的原理和计算步骤。  相似文献   

The role of moisture cycling in the weathering of a quartz chlorite schist in a tropical environment: findings of a laboratory simulation   总被引：1，自引：0，他引：1  

Tony Wells  Philip Binning  Garry Willgoose 《地球表面变化过程与地形》2005,30(4):413-428

Long‐term weathering of a quartz chlorite schist via wetting and drying was studied under a simulated tropical climate. Cubic rock samples (15 mm × 15 mm × 15 mm) were cut from larger rocks and subjected to time‐compressed climatic conditions simulating the tropical wet season climate at the Ranger Uranium Mine in the Northern Territory, Australia. Fragmentation, moisture content and moisture uptake rate were monitored over 5000 cycles of wetting and drying. To determine the impact of climatic variables, five climatic regimes were simulated, varying water application, temperature and drying. One of the climatic regimes reproduced observed temperature and moisture variability at the Ranger Uranium Mine, but over a compressed time scale. It is shown that wetting and drying is capable of weathering quartz chlorite schist with changes expected over a real time period of decades. While wetting and drying alone does produce changes to rock morphology, the incorporation of temperature variation further enhances weathering rates. Although little fragmentation occurred in experiments, significant changes to internal pore structure were observed, which could potentially enhance other weathering mechanisms. Moisture variability is shown to lead to higher weathering rates than are observed when samples are subjected only to leaching. Finally, experiments were conducted on two rock samples from the same source having only subtle differences in mineralogy. The samples exhibited quite different weathering rates leading to the conclusion that our knowledge of the role of rock type and composition in weathering is insufficient for the accurate determination of weathering rates. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Rock albedo and monitoring of thermal conditions in respect of weathering: some expected and some unexpected results     

Kevin Hall  B. Staffan Lindgren  Peter Jackson 《地球表面变化过程与地形》2005,30(7):801-811

Broadly speaking, there is, at least within geomorphic circles, a general acceptance that rocks with low albedos will warm both faster and to higher temperatures than rocks with high albedos, reflectivity influencing radiative warming. Upon this foundation are built notions of weathering in respect of the resulting thermal differences, both at the grain scale and at the scale of rock masses. Here, a series of paving bricks painted in 20 per cent reflectivity intervals from black through to white were used to monitor albedo‐influenced temperatures at a site in northern Canada in an attempt to test this premise. Temperatures were collected, for five months, for the rock surface and the base of the rock, the blocks being set within a mass of local sediment. Resulting thermal data did indeed show that the dark bricks were warmer than the white but only when their temperatures were equal to or cooler than the air temperature. As brick temperature exceeded that of the air, so the dark and light bricks moved to parity; indeed, the white bricks frequently became warmer than the dark. It is argued that this ‘negating’ of the albedo influence on heating is a result of the necessity of the bricks, both white and black, to convect heat away to the surrounding cooler air; the darker brick, being hotter, initially convects faster than the white as a product of the temperature difference between the two media. Thus, where the bricks become significantly hotter than the air, they lose energy to that air and so their respective temperatures become closer, the albedo influence being superceded by the requirement to equilibrate with the surrounding air. It is argued that this finding will have importance to our understanding of weathering in general and to our perceptions of weathering differences between different lithologies. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Microorganisms in Lianxian lateritic gold deposit in Guangdong and their effects on leaching of heavy metals     

陈炳辉刘琥琥  毋福海徐文烈 《中国地球化学学报》2005,24(2):144-148

Microorganisms in the lateritic profiles of the Lianxian gold deposit in Guangdong were cultured, isolated and identified. The microorganisms include bacteria such as Bacillus, Enterobacter, Pseudomonas, Lactobacillus, Actinetobacter, Aeromona, Listeria, Agrobacteriura, Cotyttebacteriurn, and Moraxella, fungi such as Penicillium, Alter naria, Cladosporium, Saccharcornyces, Mucor, and the chemoautotrophic Thiobacillu.~. It is shown in a leaching experiment that the microorganisms can accelerate the leaching of Cu, Cd, Zn, and that the G- bacteria are most efficient for leaching Cu, Zn and the G^ bacteria are better for leaching Cd.  相似文献   

Saprolite Remnants as Indicators of Pre-Glacial Landform Genesis in Southeast Sweden   总被引：3，自引：0，他引：3  

Mats Olvmo  Karna Lidmar-Bergström  Kerstin Ericson  Johan M. Bonow 《Geografiska Annaler: Series A, Physical Geography》2005,87(3):447-460

Twenty‐six sites with remnants of gravelly saprolites (grus) have been located in southeast Sweden. Joint block hills (castle kopjes) and steep rock walls with weathered joints as well as rounded boulders are documented to have an origin in deep weathering and subsequent stripping of saprolites. The saprolite remnants and landforms result from the fragmentation of the re‐exposed sub‐Cambrian peneplain along fracture systems. Only shallow saprolites occur on the elevated intact parts of the sub‐Cambrian peneplain, while saprolites up to 20 m thick are encountered in areas where the sub‐Cambrian peneplain is fractured and dissected. Neogene uplift with reactivation of the weathering system is thought to be the main cause of saprolite formation. Deep weathering is thus judged to have been the major agent of landform formation in the study area, while glacial and glaciofluvial erosion has contributed mainly by stripping saprolites, detaching corestones, and plucking joint blocks along weathered joints.  相似文献   

应用遥感方法研究黄河三角洲地表蒸发及其与下垫面关系   总被引：10，自引：1，他引：10  

崔亚莉  徐映雪  邵景力  张长春 《地学前缘》2005,12(Z1):159-165

文中主要应用遥感方法计算了黄河三角洲地表蒸发量及其地表特征参数。地表特征参数及其合理组合揭示出黄河三角洲下垫面的基本特征:农田植被指数和天然植被的植被指数有不同的变化规律,下垫面覆盖度低,裸地较多,地表较湿润,蒸发量较大。蒸发量时空分布主要受下垫面条件控制,滨海裸地和受人类活动影响较大的农田等地蒸发量较大,年际平均蒸发量在570~860 mm之间。  相似文献