DEM analysis of the crack propagation in brittle clays under uniaxial compression tests   总被引：2，自引：0，他引：2  

Luis F. Vesga  Luis E. Vallejo  Sebastian Lobo‐Guerrero 《国际地质力学数值与分析法杂志》2008,32(11):1405-1415

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Numerical estimation of REV and permeability tensor for fractured rock masses by composite element method   总被引：2，自引：0，他引：2  

S.‐H. Chen  X.‐M. Feng  S. Isam 《国际地质力学数值与分析法杂志》2008,32(12):1459-1477

The Monte Carlo method is used to generate parent stochastic discrete fracture network, from which a series of fractured rock samples of different sizes and orientations are extracted. The fracture network combined with a regular grid forms composite element mesh of the fractured rock sample, in which each composite element is composed of sub‐elements incised by fracture segments. The composite element method (CEM) for the seepage is implemented to obtain the nodal hydraulic potential as well as the seepage flow rates through the fractured rock samples. The application of CEM enables a large quantity of stochastic tests for the fractured rock samples because the pre‐process is facilitated greatly. By changing the sizes and orientations of the samples, the analysis of the seepage characteristics is realized to evaluate the variation of the permeability components, the existence of the permeability tensor and the representative element volume. The feasibility and effectiveness are illustrated in a numerical example. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Biaxial test simulations using a packing of polygonal particles   总被引：1，自引：0，他引：1  

A. A. Peña  A. Lizcano  F. Alonso‐Marroquin  H. J. Herrmann 《国际地质力学数值与分析法杂志》2008,32(2):143-160

The mechanical response of cohesionless granular materials under monotonic loading is studied by performing molecular dynamic simulations. The diversity of shapes of soil grains is modelled by using randomly generated convex polygons as granular particles. Results of the biaxial test obtained for dense and loose media show that samples achieve the same void ratio at large strains independent of their initial density state. This limit state resembles the so‐called critical state of soil mechanics, except for some stress fluctuations, which remain for large deformations. These fluctuations are studied at the micro‐mechanical level, by following the evolution of the co‐ordination number, force chains and the fraction of the sliding contacts of the sample. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Flexural isostatic response of the Alps to increased Quaternary erosion recorded by foreland basin remnants,SE France     

Jean‐Daniel Champagnac  Peter Van Der Beek  Gaël Diraison  Samuel Dauphin 《地学学报》2008,20(3):213-220

We test the hypothesis that flexural isostatic compensation of the mass removed by enhanced Quaternary erosion is responsible for uplift of the Western European Alps and their forelands. We use two well‐preserved and well‐dated (1.8 Ma) abandonment surfaces of foreland basin remnants in SE France (the Chambaran and Valensole plateaux) as passive benchmarks for tilting of the foreland. Estimating their initial slope from morphometric scaling relationships, we determine bulk post‐depositional tilting of 0.5–0.8% for these surfaces. The calculated isostatic response of the Alpine lithosphere to erosional unloading, using the method recently proposed by Champagnac et al. [Geology 35 (2007) 195–198] , yields a predicted tilting of 0.3–0.4% in the considered areas, explaining approximately half of the determined post‐depositional tilting. Such long‐term deformation being insensitive to cyclic loading/unloading because of glaciations, we suspect the other half to be related to as yet undetermined long‐wavelength and long‐lived tectonic process(es).  相似文献   

GEOGRAPHIA POLONICA AND STUDIES IN GEOGRAPHY     

Huey Louis Kostanick 《The Professional geographer》1969,21(1):39-41

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Carbon dioxide partial pressures in North Pacific surface waters — Time variations     

Louis I. Gordon  P. Kilho Park  Stephen W. Hager  Timothy R. Parsons 《Journal of Oceanography》1971,27(3):81-90

Observations were made of time variations of the carbon dioxide partial pressures (Pco₂) of the atmosphere and surface sea waters in the Pacific subarctic region. Data were obtained on a cruise of the USC & GSSSURVEYOR in October, 1968 and on the TRANSPAC expedition of the CNAVENDEAVOUR in March–April, 1969. A rise in surface water Pco₂ of 18×10^–6 atm occurred in a period of 30–45 days in March–April due principally to spring warming of surface waters. An average increase of 60×10^–6 atm occurred between October, 1968 and March, 1969 as a result mainly of cessation of summer phytoplankton production and the onset of winter-storm-driven vertical mixing. Because the air-sea Pco₂ gradient not only changed appreciably in magnitude but also changed sign, there are important implications for calculations of air-sea exchange of carbon dioxide on the ocean wide scale.Data contained in this paper comprise part of a dissertation to be submitted by Louis I. Gordon in partial fulfillment of the requirements for the Ph. D. at Oregon State University.  相似文献   

Potentiometric determination of calcium and magnesium in seawater     

Jean Lebel  Alain Poisson   《Marine Chemistry》1976,4(4):321-332

Methods are described for the complexometric determination of calcium and magnesium in seawater, using an amalgamated silver electrode for end-point detection. In the presence of a small amount of mercury(II)-chelonate, the amalgamated silver electrode serves as a pM indicator during the complexometric titration, the Hg complex being stronger than Ca, Mg and Sr complexes. Calcium is determined by titration with EGTA, calcium+magnesium+strontium by titration with EDTA and magnesium is obtained by difference. Average values of 0.02120 (standard deviation 0.00004) for Ca:Cl‰ and 0.06671 (standard deviation 0.00014) for Mg:Cl‰ were obtained for samples from tropical North Atlantic Ocean.  相似文献   

An improved multiple-frequency method for measuring in situ target strengths     

Conti  Stephane G.; Demer  David A.; Soule  Michael A.; Conti  Jean H.E. 《ICES Journal of Marine Science》2005,62(8):1636-1646

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Bioaccumulation et elimination du ⁶⁵Zn par Gammarus aequicauda martimov     

Jean Pierre Baudin 《Marine environmental research》1982,7(3):227-233

Uptake of ⁶⁵Zn by Gammarus aequicauda results in a concentration factor of approximately 50 and it is characterised by a maximal accumulation level attained as early as the third day of the experiment. After ingestion by the gammarids of twenty contaminated meals which are distributed over a 45-day period, a transfer of ⁶⁵Zn between the food and the consumer can be observed but there is no sign of the biomagnification phenomenon. The retention rate of the radionuclide is only about 1·5% and the ⁶⁵Zn concentration in the gammarids remains markedly inferior to that of the ingested food.The elimination of the ⁶⁵Zn fixed directly from water takes place according to an exponential model which corresponds to the existence of three biological half-lives of the radionuclide, $\text{Tb}{}_1\text{? 0·5 day, Tb}{}_2\text{? 3·5 days and Tb}{}_3\text{? days}$. The excretion of ⁶⁵Zn accumulated from food is a simple exponential phenomenon which corresponds to only one biological half-life of approximately 17 days.  相似文献   

A sample changer for automated seawater nutrient analysis systems     

Richard D. Tomlinson  Louis I. Gordon 《Ocean Engineering》1973,2(4):179-182

An automatic sample changer based upon a commercially available 20-port rotary valve has been developed for use in automated seawater nutrient analyses. All parts exposed to seawater are of stainless steel, Teflon®, or Kel-F®. The sampler has proven to be rugged and efficient in both shore and shipboard laboratories.  相似文献