This paper deals with prediction of collapse settlements due to saturation of rockfill, mainly in embankment dams. After some brief considerations about the physical basis and the practical importance of the phenomenon, a research program on this subject developed in LNEC is presented. Using non linear elastic models (and adequate loading and unloading-reloading criteria) whose parameters are quantified by laboratory tests and data from a field test, it is concluded that is possible and reliable to predict collapse settlements due to saturation of rockfill embankments. As a result of a parametric study the relative importance of the different parameters in the model is analyzed. 相似文献
Oil from the Oligocene oil sands of the Lower Ganchaigou Formation in the Northern Qaidam Basin and the related asphaltenes was analyzed using bulk and organic geochemical methods to assess the organic matter source input, thermal maturity, paleo-environmental conditions, kerogen type, hydrocarbon quality, and the correlation between this oil and its potential source rock in the basin. The extracted oil samples are characterized by very high contents of saturated hydrocarbons (average 62.76%), low contents of aromatic hydrocarbons (average 16.11%), and moderate amounts of nitrogen–sulfur–oxygen or resin compounds (average 21.57%), suggesting that the fluid petroleum extracted from the Oligocene oil sands is of high quality. However, a variety of biomarker parameters obtained from the hydrocarbon fractions (saturated and aromatic) indicate that the extracted oil was generated from source rocks with a wide range of thermal maturity conditions, ranging from the early to peak oil window stages, which are generally consistent with the biomarker maturity parameters, vitrinite reflectance (approximately 0.6%), and Tmax values of the Middle Jurassic carbonaceous mudstones and organic-rich mudstone source rocks of the Dameigou Formation, as reported in the literature. These findings suggest that the studied oil is derived from Dameigou Formation source rocks. Furthermore, the source- and environment-related biomarker parameters of the studied oil are characterized by relatively high pristane/phytane ratios, the presence of tricyclic terpanes, low abundances of C27 regular steranes, low C27/C29 regular sterane ratios, and very low sterane/hopane ratios. These data suggest that the oil was generated from source rocks containing plankton/land plant matter that was mainly deposited in a lacustrine environment and preserved under sub-oxic to oxic conditions, and the data also indicate a potential relationship between the studied oil and the associated potential source rocks. The distribution of pristane, phytane, tricyclic terpanes, regular steranes and hopane shows an affinity with the studied Oligocene Lower Ganchaigou Formation oil to previously published Dameigou Formation source rocks. In support of this finding, the pyrolysis–gas chromatography results of the analyzed oil asphaltene indicate that the oil was primarily derived from type II organic matter, which is also consistent with the organic matter of the Middle Jurassic source rocks. Thus, the Middle Jurassic carbonaceous mudstones and organic rock mudstones of the Dameigou Formation could be significantly contributing source rocks to the Oligocene Lower Ganchaigou Formation oil sand and other oil reservoirs in the Northern Qaidam Basin.
We revisit the evolution of the scale factor in a flat FLRW spacetime with a new generalized decay rule for the dynamic -term under modified theories of gravity. It analyzes certain cosmological parameters and examines their behaviours in this generalized setting which includes several decay laws in the literature. We have also obtained observational constraints on various model parameters and estimated the present values of cosmological parameters , , , and have discussed with various observational results. Finite time past and future singularities in this model are also discussed. 相似文献
The astrophysical S-factor of the experimental cross section data of the main reactions in the proton–proton chain, i.e. 3He(3He,2p)4He, 3He(4He,γ)7Be and 7Be(p,γ)8B, are reanalyzed by using the exact tunneling probability in nuclear reactions. Our goal is to test this treatment in finding the reaction rate per pair for non-resonant reactions. At low temperatures, the exact treatment is identical to the standard formalism but diverges at higher temperatures. 相似文献
In this work, a standard solar model is computed with new reaction rates that take into account the exact astrophysical S-factor, Se for the 3He(3He,2p)4He, 3He(α,γ)7Be and 7Be(p,γ)8B reactions. The exact S-factor which is valid for all energies is an improved version of the S-factor in the lower-energy approximation (Yusof and Kassim in Astrophys. Space Sci., 2009b). The effects of these new nuclear reaction rates on the solar neutrino fluxes are then discussed by comparing this model to a solar model computed with the standard NACRE reaction rates (Angulo et al. in Nucl. Phys. A. 656:3, 1999). The new reaction rates are found to decrease the neutrinos flux for 7Be and 8B by about 6% and 16%, respectively. A solar model is also computed with the reaction rates of the LUNA collaboration for 14N(p,γ)15O (Formicola et al. in Phys. Lett. B 591:61, 2004). In this case, a clear decrease of the fluxes for 13N and 15O is observed to be in good agreement with previous results (see e.g. Bahcall et al. in Astrophys. J. 621:L88, 2005). 相似文献
Four dense Scandinavian limestones were analyzed to determine their mechanical properties. The generation of dust (? 10 μm) and fines (? 90 μm) during a closed circuit vertical roller mill comminution process was correlated with the calcite crystal size distributions of each limestone. Thin sections were analyzed and by means of stereology the calcite crystal size distributions for each limestone was measured. The dust generation of limestones is governed by a surface abrasive mechanism (R2 = 0.99) and the production of fines is governed by the mechanical strength of limestones (R2 = 0.99). The overall limestone degradation mechanism is predominantly controlled by the calcite cleavage planes which reduce the power consumption during the comminution process. This study is the first step in determining the influence of limestone texture on the wear rates in heterogenous raw mixes used in closed circuit comminution equipment. 相似文献
The influence of hydroxybenzoic acids (HAHn), namely p-hydroxybenzoic acid (4-hydroxybenzoic acid, HPhbH) and protocatechuic acid (3,4-dihydroxybenzoic acid, HProtoH2), on the adsorption of europium(III) onto α,γ-Al2O3 particles is studied as a function of acid concentration. After measuring the adsorption edge of the Eu(III)/α,γ-Al2O3 binary system, and using the previously studied binary component system Eu(III)/HAHn—Moreau et al. (2015) Inorg. Chim. Acta432, 81—, and HAHn/α,γ-Al2O3—Moreau et al. (2013) Colloids Surf. A435, 97—, it is evidenced that HPhbH does not enhance Eu(III) adsorption onto α,γ-Al2O3 in the Eu(III)/HPhbH/α,γ-Al2O3 ternary system. Conversely, HProtoH2 enhances Eu(III) adsorption onto α,γ-Al2O3 in the Eu(III)/HProtoH2/α,γ-Al2O3 ternary system. Adsorption of the acids are also found higher in the Eu(III)/acid/α,γ-Al2O3 ternary systems as compared with the corresponding binary systems assessing synergetic effects. For high HPhbH concentrations, a ternary surface species involving ≡AlOH surface sites, Eu(III), and PhbH– is evidenced by time-resolved luminescence spectroscopy (TRLS). However, in the Eu(III)/HProtoH2/α,γ-Al2O3 ternary system, chemical environment of Eu(III) is found to be very close to that in the Eu(III)/HProtoH2 binary system. Ternary surface species could not be evidenced in the Eu(III)/HProtoH2/α,γ-Al2O3 ternary system with TRLS because of the very short decay time of Eu(III) in the presence of protocatechuic acid. 相似文献
The Masila Basin is an important hydrocarbon province in Yemen, but the origin of hydrocarbons and their generation history are not fully understood. In this regard, 10 crude oils from different petroleum reservoir sections in the Masila Basin were characterized by a variety of biomarker and non-biomarker parameters using GC, GC-MS and stable carbon isotope techniques. Oils from the Masila Basin display pristane/phytane (Pr/Ph) ratios ranging from 1.7 to 2.0, low sulfur content, high C35 homohopane index, relatively high C27 sterane concentrations and relatively high tricyclic terpanes suggesting a marine clay source rock that was deposited in mildly anoxic to suboxic conditions with dominantly algal organic matter. C29 20S/(20S + 20R) steranes and ββ/(ββ + αα) sterane ratios indicate that the Masila oils have reached peak oil window maturity. Another related feature of these oils is the absence of 18α (H)-oleanane, which suggests a source age older than Cretaceous. The carbon isotope compositions are similar to those of the potential source rocks, which range from −25.4‰ to −28.3‰, indicating a marine environment. The new data presented in this paper suggest that the Masila oils constitute one oil family and that the oil originated from the Upper Jurassic Madbi source rock in the basin. 相似文献
The performance of a Wells turbine with various non-uniform tip clearances was investigated using computational fluid dynamics (CFD). The investigation was performed on numerical models of a NACA0020 blade profile under steady flow conditions. The performance of turbines with uniform and non-uniform tip clearances was compared. The results were also compared with experimental results in literature. It was shown that the performance of turbine with non-uniform tip clearance is similar with that of turbine with uniform one in terms of torque coefficient, input power coefficient, and efficiency. However, the turbine with non-uniform tip clearance seems to have a preferable overall performance. An investigation on the flow-field around the turbine blade was performed in order to explain the phenomena. 相似文献
