Roughness control on hydraulic conductivity in fractured rocks   总被引：1，自引：0，他引：1  

Laura Scesi  Paola Gattinoni 《Hydrogeology Journal》2007,15(2):201-211

The influence of joint roughness on the typologies of fluid flow inside fractures is well known and, thanks to experiences in the field of hydraulics, it has been studied from both a physical and mathematical point of view. Nevertheless, the formulations adopted by traditional hydraulic models are hardly applicable in the geological field, because of the difficulty encountered in the roughness parameter estimation. Normally this parameter can be estimated using the joint roughness coefficient (JRC), which considers both the asperity height and its regularity and directional trend. The main advantage in using the JRC arises from the fact that it can easily be obtained from geological-technical surveys and from comparison with the standard Barton profiles. Some relationships have been built up that allow for the estimation of the hydraulic conductivity tensor (an essential parameter for understanding water flow in fractured rock masses), not only as a function of traditional parameters like aperture, spacing, dip and dip direction, etc., but also of joint roughness, precisely expressed in terms of the roughness coefficient. These relationships have been studied initially from a theoretical point of view and then practically, through laboratory investigations.

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Resumen  Se conoce muy bien la influencia de la rugosidad de las grietas en las tipologías del flujo de fluidos a lo interior de las fracturas y gracias a las experiencias en el campo de hidráulica ha sido posible estudiarla desde puntos de vista matemáticos y físicos. Sin embargo, las formulaciones adoptadas por los modelos hidráulicos tradicionales tienen poca aplicabilidad en el campo geológico debido a la dificultad relacionada con la estimación del parámetro de rugosidad. Normalmente este parámetro puede estimarse usando el coeficiente de rugosidad de grieta (JRC) el cual considera tanto la altura de la aspereza como su regularidad y tendencia direccional. La principal ventaja de utilizar el JRC se deriva del hecho que puede obtenerse fácilmente de levantamientos técnico-geológicos y de la comparación con los perfiles Standard Barton. Se han construido algunas relaciones que permiten la estimación del tensor de conductividad hidráulica (un parámetro esencial para el entendimiento del flujo de agua en masas de roca fracturadas), no solo en función de parámetros tradicionales como apertura, espaciado, buzamiento y dirección de buzamiento, etc., sino también en función de la rugosidad de la grieta estimada con precisión en términos del coeficiente de rugosidad. Estas relaciones se han estudiado inicialmente desde un punto de vista teórico y luego de modo práctico a través de investigaciones de laboratorio.

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Résumé  L’influence de la rugosité des joints sur les types d’écoulement de fluide dans les fractures est bien connue et a été étudiée aussi bien du point de vue physique que mathématique grace à des expériences menées dans le domaine de l’hydraulique. Cependant les formulations adoptées dans les modèles hydrauliques traditionnels sont difficilement applicables dans le domaine de la géologie à cause de la difficulté rencontrée pour estimer la rugosité. Ce paramètre peut normalement être apprécié grace au coefficient de rugosité du joint (JRC), lequel prend en compte à la fois la hauteur de l’aspérité ainsi que sa régularité et sa direction. Le principal avantage dans l’utilisation du JRC réside dans le fait qu’il peut facilement être obtenu à partir d’études techniques-géologiques et par comparaison avec la classification de Barton. Des relations qui permettent une estimation du tenseur de conductivité hydraulique (un paramètre essentiel pour comprendre l’écoulement de l’eau dans les masses rocheuses fracturées) ont été élaborées, pas seulement en fonction de paramètres traditionnels tels que l’ouverture, l’espacement, l’inclinaison et la direction d’inclinaison, etc , mais aussi en prenant en compte la rugosité des joints à travers le coefficient de rugosité. Ces relations ont initialement été étudiées d’un point de vue théorique puis expérimentalement à travers des recherches en laboratoire.

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1975年8月河南省特大暴雨雨强极值的重新估算   总被引：1，自引：0，他引：1  

王兴荣  高守亭 《热带气象学报》2007,23(2):196-200

通过对云中气载液态水含量以及水汽和气载液态水之间的平衡方程的讨论,建立了改进的可降水量Ia公式。按照改进的公式,重新估算了1975年8月河南省特大暴雨7日20时雨强。结果表明,分别以遂平气象站记录的8 m/s和按物象估算的12 m/s地面风速为基础的改进的板桥水库附近8月7日20时雨强估算值Iae1=75.0 mm/h和Iae1=95.8 mm/h很接近实际的雨强极值Ioe=99.7 mm/h。  相似文献   

Errors and Correction of Precipitation Measurements in China   总被引：2，自引：0，他引：2  

任芝花  黎明琴 《大气科学进展》2007,24(3):449-458

In order to discover the range of various errors in Chinese precipitation measurements and seek a correction method, 30 precipitation evaluation stations were set up countrywide before 1993. All the stations are reference stations in China. To seek a correction method for wind-induced error, a precipitation correction instrument called the ＂horizontal precipitation gauge＂ was devised beforehand. Field intercomparison observations regarding 29,000 precipitation events have been conducted using one pit gauge, two elevated operational gauges and one horizontal gauge at the above 30 stations. The range of precipitation measurement errors in China is obtained by analysis of intercomparison measurement results. The distribution of random errors and systematic errors in precipitation measurements are studied in this paper. A correction method, especially for wind-induced errors, is developed. The results prove that a correlation of power function exists between the precipitation amount caught by the horizontal gauge and the absolute difference of observations implemented by the operational gauge and pit gauge. The correlation coefficient is 0.99. For operational observations, precipitation correction can be carried out only by parallel observation with a horizontal precipitation gauge. The precipitation accuracy after correction approaches that of the pit gauge. The correction method developed is simple and feasible.  相似文献   

航空地球物理勘查科技创新与应用     

熊盛青 《地质力学学报》2020,26(5):791-818

简要回顾了中国航空物探技术的发展历程，重点阐述了21世纪以来、尤其是"十一五"以来国内航空物探的主要技术创新与应用成果，并对今后发展趋势进行了分析与预测。为满足国家与社会需求，"十一五"以来，中国的航空物探技术，尤其是航磁多参量、矢量测量、航空重力测量和时间域航空电磁测量技术得到快速发展；在航空物探技术创新过程中，航空物探资料的综合研究和应用得到了加强，在基础地质、固体矿产勘查与评价、能源勘查与评价等方面取得了重要成果，在地下水资源调查、工程地质勘查、环境地质调查等方面显示出了良好的应用前景。为满足国家资源勘查和环境评价对航空探测技术的需求，未来中国航空物探测量系统的分辨率、稳定性和实用性将进一步提高，航空物探在加强基础地质、固体矿产勘查、能源勘查等传统领域应用的基础上，将拓展及加强在深地探测、深海探测、深部地热调查、水资源调查、地质灾害调查、军事及测绘等领域的应用。   相似文献   

On the use of microtremor recordings in seismic microzonation   总被引：4，自引：0，他引：4  

M. Bour  D. Fouissac  P. Dominique  C. Martin 《Soil Dynamics and Earthquake Engineering》1998,17(7-8):465-474

Experimental methods involving microtremor recordings are useful for determining site effects in regions of moderate seismic activity where ground motion records are few, and in urban or industrial contexts where the noise level is high. The aim of this study is to establish a microzonation by using the Nogoshi–Nakamura method,[1, 2] a simple experimental technique based on microtremor recordings. Since the physical phenomena underlying the method are only partially understood, the spectral responses obtained cannot be used alone. We, therefore, complete our experimental results by comparing them with the solutions of a one-dimensional numerical simulation (SHAKE91).[3, 4] The experimental programme was carried out on a plain near the Rhone Delta (South of France). H/V spectral ratios were calculated at 137 noise measurement points. In addition, we were able to compute the numerical transfer functions from soil columns defined by geotechnical characteristics inside the studied region. A comparison of the results obtained by the experimental and numerical methods showed that the fundamental frequencies are in good agreement, but that the amplitudes obtained by the two techniques are sometimes different. The analysis of H/V spectral ratios enabled us to establish maps to characterize the region: a resonance frequency map and maps of amplification levels as a function of frequency range, leading to a seismic microzonation for the whole of the region.  相似文献   

航空物探剖面图数据提取法     

邢俊兵 《黄金地质》1998,4(2):55-57

我国的主要成矿区带上有着丰富的航空物探资料,而这些资料多以模拟方式进行记录,所以,我们在日常工作中所收集到的资料多是平面剖面图或平面等值线图。提供一种用数字化对平面剖面图进行数据提取的方法,为平面剖面图的二次利用提供了条件。  相似文献   

A comparison of estimated and calculated effective porosity   总被引：1，自引：1，他引：0  

Daniel B. Stephens  Kuo-Chin Hsu  Mark A. Prieksat  Mark D. Ankeny  Neil Blandford  Tracy L. Roth  James A. Kelsey  Julia R. Whitworth 《Hydrogeology Journal》1998,6(1):156-165

 Effective porosity in solute-transport analyses is usually estimated rather than calculated from tracer tests in the field or laboratory. Calculated values of effective porosity in the laboratory on three different textured samples were compared to estimates derived from particle-size distributions and soil–water characteristic curves. The agreement was poor and it seems that no clear relationships exist between effective porosity calculated from laboratory tracer tests and effective porosity estimated from particle-size distributions and soil–water characteristic curves. A field tracer test in a sand-and-gravel aquifer produced a calculated effective porosity of approximately 0.17. By comparison, estimates of effective porosity from textural data, moisture retention, and published values were approximately 50–90% greater than the field calibrated value. Thus, estimation of effective porosity for chemical transport is highly dependent on the chosen transport model and is best obtained by laboratory or field tracer tests. Received, March 1997 · Revised, August 1997 · Accepted, August 1997  相似文献   

A method of searching for radial velocity anomalies in the lower mantle using interfering signals     

C. Wright  J. A. Lyons 《Pure and Applied Geophysics》1980,119(1):118-136

Radial velocity anomalies in the lower mantle that give rise to triplications in the travel-time curve for short-periodP waves will produce arrivals havingdT/d values that differe by roughly 0.2–0.5 s/deg. The first two arrivals associated with such triplications will be separated by less than one second over a distance range of 4°–10° they may not, therefore, be separable visually on single seismograms, so that their presence can only be inferred from some measurable property that depends on their mutual interference. If there are lateral variations in the regions of anomalous velocity gradients, the interfering signals will also have different azimuths of arrival. Using two synthetic wavelets we have investigated the effect of interference on bothdT/d and azimuth measurements at the Yellowknife Array. We found that if the interfering pulses have a dominant frequencyv, there is a range of time separations (0.30/v0.55/v) over which the measureddT/d and azimuth values may fluctuate by much more than the differences indT/d and azimuth between the interfering signals. We have evaluated the following empirically defined functions for three different primary signals, and for three different relative amplitudes of the interfering signals:f (t), the drift function, which expresses how the measured slownesses,p, and azimuths, , differ from the slownesses and azimuths of the primary wavelets; f(), the range function, which describes the behaviour of the upper and lower bounds ofp and as a function of the difference in arrival times of the signals, andf , studied the properties of these functions, and have outlined how these properties provide criteria based on the numerical and statistical characteristics of the arrival vectors, and on the waveform of the signal that will enable small radial velocity anomalies to be more clearly delineated.Contribution No. 863 from the Earth Physics Branch.  相似文献   

The thermal structure of the Dvurechenskii mud volcano and its implications for gas hydrate stability and eruption dynamics     

T. Feseker  T. Pape  K. Wallmann  S.A. Klapp  F. Schmidt-Schierhorn  G. Bohrmann 《Marine and Petroleum Geology》2009

The sediment temperature distribution at mud volcanoes provides insights into their activity and into the occurrence of gas hydrates. If ambient pressure and temperature conditions are close to the limits of the gas hydrate stability field, the sediment temperature distribution not only limits the occurrence of gas hydrates, but is itself influenced by heat production and consumption related to the formation and dissociation of gas hydrates. Located in the Sorokin Trough in the northern Black Sea, the Dvurechenskii mud volcano (DMV) was in the focus of detailed investigations during the M72/2 and M73/3a cruises of the German R/V Meteor and the ROV Quest 4000 m in February and March 2007. A large number of in-situ sediment temperature measurements were conducted from the ROV and with a sensor-equipped gravity corer. Gas hydrates were sampled in pressurized cores using a dynamic autoclave piston corer (DAPC). The thermal structure of the DMV suggests a regime of fluid flow at rates decreasing from the summit towards the edges of the mud volcano, accompanied by intermittent mud expulsion at the summit. Modeled gas hydrate dissociation temperatures reveal that the gas hydrates at the DMV are very close to the stability limits. Changes in heat flow due to variable seepage rates probably do not result in changes in sediment temperature but are compensated by gas hydrate dissociation and formation.  相似文献   

Field Detection of Chlorophyll-a Concentration in the Sea Surface Layer by an Airborne Oceanographic Lidar     

LIU Zhishen  MA Sen  WANG Xin  LI Zhigang 《中国海洋大学学报(英文版)》2008,7(1)

An airborne oceanographic lidar, with a frequency-tripled Q-switched Nd: YAG laser of 355 nm, has been designed to measure chlorophyll-a (Chl-a) concentration in the sea surface layer by the Ocean Remote Sensing Institute, OUC. The field experiment was carried out in the bay which is located south of the Liaodong Peninsula on the 10th of September 2005. After the flight, the raw data were processed and analyzed by the fluorescence-to-Raman ratio method with seawater attenuation coefficients calculated from signal profiles. The results of Chl-a concentration measurements by lidar are shown. The measurements in clear sea water were also compared with those of Chl-a concentration by a Moderate Resolution Imaging Spectroradiometer (MODIS).  相似文献