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891.
Eduardo E. Alonso Sarah M. Springman Charles W. W. Ng 《Geotechnical and Geological Engineering》2008,26(6):817-826
Two large-scale “in situ” demonstration experiments and their instrumentation are described. The first test (FEBEX Experiment)
involves the hydration of a compacted bentonite barrier under the combined effect of an inner source of heat and an outer
water flow from the confining saturated granite rock. In the second case, the progressive de-saturation of Opalinus clay induced
by maintained ventilation of an unlined tunnel is analyzed. The paper shows the performance of different sensors (capacitive
cells, psychrometers, TDR’s) and a comparison of fill behaviour with modelling results. The long term performance of some
instruments could also be evaluated specially in the case of FEBEX test. Capacitive sensors provide relative humidity data
during long transient periods characterised by very large variations of suction within the bentonite. 相似文献
892.
Alessandro Tarantino Andrew M. Ridley David G. Toll 《Geotechnical and Geological Engineering》2008,26(6):751-782
This paper presents a review of techniques for field measurement of suction, water content, and water hydraulic conductivity
(permeability). Main problems in the use of field tensiometers are addressed and hints on how to improve tensiometer performance
are given. Advantages and limitations of instruments for indirect measurement of suction including electrical conductivity
sensors, thermal conductivity sensors, dielectric permittivity sensors, filter paper, and psychrometer are discussed. Techniques
for water content measurement based on dielectric methods are then presented. These include time and amplitude domain reflectometry
and capacitance. Finally, a brief overview of methods for measurement of water permeability in the field is presented. 相似文献
893.
894.
895.
贵州遵义牛蹄塘组黑色岩系的硒同位素变化及其环境指示初探 总被引:4,自引:0,他引:4
西南早寒武世牛蹄塘组是分布在中国南方扬子地台的一套黑色岩系,区域上发育有典型富集多金属元素的硫化物矿化层.选取遵义松林小竹牛蹄塘组下部富硒、钼、镍等元素的黑色岩系剖面,利用Se同位素初步探讨了该剖面岩石的沉积环境和硒的可能来源.结果表明,小竹牛蹄塘组下部剖面黑色岩系的δ82/76SeSRM3149比值变化较大,下部底层含碳斑脱岩与磷块岩的变化范围在-4.35‰~ 4.11‰之间;中间镍钼层及碳质页岩、碳质碳酸盐岩的δ82/76SeSRM3149变化范围窄,平均值为0.9‰±0.23‰(n=4);上层碳质页岩为-1.24‰.结合已发表的钼同位素数据,认为中间岩石沉积于缺氧/无氧环境,但存在盆地海水与热液或充氧水团的混合;下层的岩石曾一度位于充氧与贫氧环境的边界面,局部岩石曾暴露地表经历了较强的风化和蚀变作用,海水中硒有可能来自底部富硒斑脱岩的氧化淋滤或海底热液.据此推测遵义松林小竹牛蹄塘组下部岩石的沉积环境极可能处在局限盆地靠近陆地的边缘部分,经历了充氧→贫氧→缺氧/无氧→贫氧的演化阶段. 相似文献
896.
滇西北雪鸡坪斑岩铜矿流体包裹体初步研究 总被引:11,自引:2,他引:9
雪鸡坪中型斑岩铜矿床位于三江地区义敦岛弧南端的中甸弧,成矿斑岩为石英闪长玢岩和石英二长斑岩,属于印支期产物。含矿岩体蚀变分带明显,由中心向外发育强硅化带→石英绢云母化带→粘土化-石英绢云母化带→青磐岩化带,工业矿体赋存于斑岩体中心强硅化和石英绢云母化带内。矿化类型以网脉状矿化为主,细脉浸染状矿化不发育。本文对主要矿化阶段石英脉中的流体包裹体系统进行了包裹体岩相学、显微测温学和激光拉曼谱学研究,发现与成矿有关的流体包裹体可以分为水溶液包裹体、CO2包裹体和含子矿物包裹体3类,子矿物主要为石盐、方解石、赤铁矿和少量CaCl2水合物及不透明硫化物。其中含子矿物包裹体均一温度为230~420℃,盐度为33.48%~75.40%NaCl equiv.,密度为1.01~1.09g/cm^3。激光拉曼光谱分析表明,包裹体的液相成分主要为H2O,气相成分为H2O和CO2。早期水溶液包裹体和CO2包裹体共生,其均一温度相近,以及纯CO2包裹体的发现,指示成矿流体存在不混溶现象,这种不混溶是由原始岩浆流体“二次沸腾”作用产生的。CO2相分离、温压条件降低和pH值升高是雪鸡坪斑岩铜矿硫化物沉淀的主要原因。晚期低温、低盐度的流体可能来源于大气降水与岩浆流体的混和,对矿化的意义不大。 相似文献
897.
898.
A numerical analysis of cyclotron instabilities is carried out by computing the dispersion relation for a three component cold plasma-beam system. Rates of growth and damping for various values of the stream density are calculated from the dispersion relation. The rates of growth and damping increase monotonically as the number density of the proton stream increases. It is found that the frequencies at the rates of maximum growth and the damping decrease slightly to lower frequencies and a sharp peak at these frequencies becomes blunt. The minimum e-folding times of an ion cyclotron wave for (a) σs = 10−4, σi = 10−2 and (b) σs = 10−1, σi = 10−2 are about 3·84 and 0·16 sec respectively in the vicinity of the equatorial plane at 6 Re, where σs and σi are the ratios of the beam density Ns and the helium ion (H6+) density Ni to the total positive ions in the plasma-beam system. 相似文献
899.
Considerable water leakages from reservoirs make it difficult to attain the planned storage capacity. In some cases water leakages give rise to suffusion followed by catastrophes. Until recently methods for locating water leakages were extremely imperfect. Geophysical methods offer good prospects in this direction. For solving these problems, it is effective to use streaming potential measurements, water flow rate observations and thermometry. Laboratory experiments were carried out in connection with the fact that water leakages from reservoirs are characterized by negative anomalies of natural currents; the more filtration discharge, the higher these anomalies are. As a result, the relationship governing the intensity of streaming potential and sand granulometric composition, electrolyte concentrations and other factors were revealed. To determine the velocity of water flowing to leakage sites, a special device, based on the relationship between the temperature of a heated body and its resistance, is applied. This device simultaneously makes it possible to measure the water medium temperature. Observations at reservoir sites were effected by moving along the reservoir non-polarizable potential electrodes and water velocity devices. Recordings were carried out automatically by the recording device of the logging apparatus. Under the conditions of ice cover on water surfaces, measurements were made through separate points by digging holes in the ice cover. Practical field observations were carried out at reservoir sites located in regions where fissured massive rocks as well as loose sediments predominate. In the first case field experiments were carried out in alpine reservoirs, in Armenia. The major water leakages were found to be concentrated on the right bank of the reservoir. In this connection it was not only possible to locate water leakage sites, but also to evaluate their relative intensity. These data were used for planning antifiltration measures. In the second case water leakages from a reservoir located in Uzbekistan in the submontane part of the Pamirs were studied. Streaming potential anomalies and high benthonic flow rates made it possible to discover high filtrations in the base and walls of the dam. Further perfection of these methods should not only permit the determination of water leakage sites and their relative intensity, but also filtration discharges in absolute units. 相似文献
900.