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131.
Triaxial strength of rock materials   总被引:4,自引:0,他引:4  
SummaryTriaxial Strength of Rock Materials An attempt is made to define the nature and purposes of triaxial strength criteria, also to outline some factors to be considered in their selection and use.Seven alternative empirical strength criteria are compared on the basis of their simplicity and their fit to data for some fifteen hundred rock and concrete specimens. Two of these, one linear and one curved, are then compared in detail. Use of the curved rather than the linear criterion resulted in a significant reduction in strength prediction error.Methods of fitting the criteria to strength data are described. The parameters of the two criteria are then used to compare and classify rocks on the basis of their triaxial strength behaviour. Possible alternative formulations of the two criteria are considered in an appendix.
ZusammenfassungDreiaxiale Festigkeit von Fels Es wird ein Versuch unternommen, Art und Zweck dreiaxialer Festigkeitskriterien zu bestimmen und einige derjenigen Faktoren zu ermitteln, die bei deren Auswahl und Anwendung von Bedeutung sind.Sieben verschiedene empirische Festigkeitskriterien werden nach ihrer Einfachheit und ihrer Übereinstimmung mit ungefähr 1500 Fels- und Betonproben verglichen. Zwei davon, eine linear und eine nicht linear, werden dann näher miteinander verglichen. Das nicht lineare Kriterium ergab, im Gegensatz zum linearen, eine bedeutende Verringerung des Fehlers in der Festigkeitsvorhersage.Methoden für die Anpassung der Kriterien an die Festigkeitsermittlungen werden beschrieben. Die Parameter der beiden Kriterien werden dann benützt, um Gesteine aufgrund ihres dreiaxialen Festigkeitverhaltens zu klassifizieren. Mögliche Alternativformulierungen der beiden Kriterien werden im Anhang behandelt.

RésuméRésistance triaxiale de matériaux rocheux Une tentative est faite pour définir la nature et le but des critères de résistance triaxiale et aussi pour dégager les quelques facteurs devant être considérés pour leur choix et leur utilisation.Sept critères empiriques différents de résistance sont comparés sur le plan simplicité et concordance des mesures faites sur 1500 échantillons de roche et de béton. Deux de ces critéres, l'un linéaire, l'autre curviligne, sont ensuite comparés dans le detail. L'utilisation du critère curviligne plutôt que linéaire entraine une réduction notable de l'erreur dans la prédiction des résistances.Des méthodes d'ajustement des critères aux résistances mesurées sont décrites. Les paramètres des deux critères retenus sont ensuite utilisés pour comparer et classer les roches en fonction de leur comportement triaxial. En annexe, quelques autres possibilités de formulation des deux critères sont explicitées.


With 7 Figures  相似文献   
132.
K. Aksnes  F.A. Franklin 《Icarus》1978,34(1):194-207
Using two sets of orbital elements and the radii of the Saturnian satellites 1 (Mimas) through 7 (Hyperion), we find that from October 1979 until August 1980 nearly 300 mutual eclipses and occultations involving these bodies will occur. To allow for the expected errors in the satellite ephemerides, we repeat these calculations in order to obtain the additional events that occur when all satellite radii (save Titan's) are increased by 1000 km. A third listing predicts eclipses of satellites by (the shadow of) the ring. Photometric observations of a large number of these events will add much precise information to our knowledge of the Saturnian system at a critical time.  相似文献   
133.
Carbon isotope fractionation factors associated with the aerobic consumption of methane (C1), ethane (C2), propane (C3), and n-butane (C4) were determined from incubations of marine sediment collected from the Coal Oil Point hydrocarbon seep field, located offshore Santa Barbara, CA. Hydrogen isotope fractionation factors for C1, C2 and C3 were determined concurrently. Fresh sediment samples from two seep areas were each slurried with sea water and treated with C1, C2, C3 or C4, or with mixtures of all four gases. Triplicate samples were incubated aerobically at 15 °C, and the stable isotope composition and headspace levels of C1-C4 were monitored over the course of the experiment. Oxidation was observed for all C1-C4 gases, with an apparent preference for C3 and C4 over C1 and C2 in the mixed-gas treatments. Fractionation factors were calculated using a Rayleigh model by comparing the δ13C and δD of the residual C1-C4 gases to their headspace levels. Carbon isotope fractionation factors (reported in ε or (α-1) × 1000 notation) were consistent between seep areas and were −26.5‰ ± 3.9 for C1, −8.0‰ ± 1.7 for C2, −4.8‰ ± 0.9 for C3 and −2.9‰ ± 0.9 for C4. Fractionation factors determined from mixed gas incubations were similar to those determined from individual gas incubations, though greater variability was observed during C1 consumption. In the case of C1 and C3 consumption, carbon isotope fractionation appears to decrease as substrate becomes limiting. Hydrogen isotope fractionation factors determined from the two seep areas differed for C1 oxidation but were similar for C2 and C3. Hydrogen isotope fractionation factors ranged from −319.9‰ to −156.4‰ for C1 incubations, and averaged −61.9‰ ± 8.3 for C2 incubations and −15.1‰ ± 1.9 for C3 incubations. The fractionation factors presented here may be applied to estimate the extent of C1-C4 oxidation in natural gas samples, and should prove useful in further studying the microbial oxidation of these compounds in the natural environment.  相似文献   
134.
Predictive vegetation modeling is defined as predicting the distribution of vegetation across a landscape based upon its relationship with environmental factors. These models generally ignore or attempt to remove spatial dependence in the data. When explicitly included in the model, spatial dependence can increase model accuracy. We develop presence/absence models for 11 vegetation alliances in the Mojave Desert with classification trees and generalized linear models, and use geostatistical interpolation to calculate spatial dependence terms used in the models. Results were mixed across models and methods, but in general, the spatial dependence terms more consistently increased model accuracy for widespread alliances. GLMs had higher accuracy in general.  相似文献   
135.
1 INTRODUCTIONOur sampling trip to Tanjung Piai wetland in2002 showed that the site had not been developed andrecognized yet as a wetland of international importance(Ramsar). Recently, our field trip in January 2005to the same site to collect sediment sam…  相似文献   
136.
An algorithm is described for generating stochastic three-dimensional (3D) cloud fields from time–height fields derived from vertically pointing radar. This model is designed to generate cloud fields that match the statistics of the input fields as closely as possible. The major assumptions of the algorithm are that the statistics of the fields are translationally invariant in the horizontal and independent of horizontal direction; however, the statistics do depend on height. The algorithm outputs 2D or 3D stochastic fields of liquid water content (LWC) and (optionally) effective radius. The algorithm is a generalization of the Fourier filtering methods often used for stochastic cloud models. The Fourier filtering procedure generates Gaussian stochastic fields from a “Gaussian” cross-correlation matrix, which is a function of a pair of heights and the horizontal distance (or “lag”). The Gaussian fields are nonlinearly transformed to give the correct LWC histogram for each height. The “Gaussian” cross-correlation matrix is specially chosen so that, after the nonlinear transformation, the cross-correlation matrix of the cloud mask fields approximately matches that derived from the input LWC fields. The cloud mask correlation function is chosen because the clear/cloud boundaries are thought to be important for 3D radiative transfer effects in cumulus.The stochastic cloud generation algorithm is tested with 3 months of boundary layer cumulus cloud data from an 8.6-mm wavelength radar on the island of Nauru. Winds from a 915-MHz wind profiler are used to convert the radar fields from time to horizontal distance. Tests are performed comparing the statistics of 744 radar-derived input fields to the statistics of 100 2D and 3D stochastic output fields. The single-point statistics as a function of height agree nearly perfectly. The input and stochastic cloud mask cross-correlation matrices agree fairly well. The cloud fractions agree to within 0.005 (the total cloud fraction is 18%). The cumulative distributions of optical depth, cloud thickness, cloud width, and intercloud gap length agree reasonably well. In the future, this stochastic cloud field generation algorithm will be used to study domain-averaged 3D radiative transfer effects in cumulus clouds.  相似文献   
137.
138.
This study investigates the use of KMnO4 doped geopolymers as controlled‐release materials for remedial applications. The geopolymers were prepared by mixing alkali activated Na‐silicate solutions, metakaolin, and various amounts of granular KMnO4. Samples were heat treated at 75 °C for 48 h. Concentrations of KMnO4 in samples 1, 2, and 3 were 1.40 × 10?1, 4.63 × 10?1, and 6.07 × 10?1 g/cm3, respectively. 1D column experiments showed that a high MnO4? release rate lasted for the first few hours, followed by a gradual decrease of MnO4? release. Neither cracks nor surface erosion of the geopolymers were observed throughout the experiments. Sample 1 approached exhaustion at the end of the Day 7. It took about 18 d for exhaustion of KMnO4 releases in samples 2 and 3. Modeling of the observed KMnO4 releases suggested diffusion and dissolution‐related fast transport as the most important mechanisms. This latter mechanism involves the creation of a connected secondary porosity in the geopolymers by dissolution of KMnO4 granules. The contribution of Fickian diffusion to the total release decreased as the KMnO4 content of the samples increased, and the dissolution mechanism became increasingly important.  相似文献   
139.
We show how to estimate the fluid permeability changes due to accumulated biopolymer within the pore space of a granular material using laboratory measurements of overall permeability, together with various well‐known quantitative measures (e.g., porosity, specific surface area, and formation factor) of the granular medium microstructure. The main focus of the paper is on mutual validation of existing theory and a synthesis of new experimental results. We find that the theory and data are in good agreement within normal experimental uncertainties. We also establish quantitative empirical relationships between seismic and/or acoustic attenuation and overall permeability for these same systems.  相似文献   
140.
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