Iron, Cu and Zn stable isotope systems are applied in constraining a variety of geochemical and environmental processes. Secondary reference materials have been developed by the Institute of Geology, Chinese Academy of Geological Sciences (CAGS), in collaboration with other participating laboratories, comprising three solutions (CAGS‐Fe, CAGS‐Cu and CAGS‐Zn) and one basalt (CAGS‐Basalt). These materials exhibit sufficient homogeneity and stability for application in Fe, Cu and Zn isotopic ratio determinations. Reference values were determined by inter‐laboratory analytical comparisons involving up to eight participating laboratories employing MC‐ICP‐MS techniques, based on the unweighted means of submitted results. Isotopic compositions are reported in per mil notation, based on reference materials IRMM‐014 for Fe, NIST SRM 976 for Cu and IRMM‐3702 for Zn. Respective reference values of CAGS‐Fe, CAGS‐Cu and CAGS‐Zn solutions are as follows: δ56Fe = 0.83 ± 0.07 and δ57Fe = 1.20 ± 0.13, δ65Cu = 0.57 ± 0.06, and δ66Zn = ?0.79 ± 0.12 and δ68Zn = ?1.65 ± 0.24, respectively. Those of CAGS‐Basalt are δ56Fe = 0.15 ± 0.07, δ57Fe = 0.22 ± 0.10, δ65Cu = 0.12 ± 0.08, δ66Zn = 0.17 ± 0.13, and δ68Zn = 0.34 ± 0.26 (2s). 相似文献
The propagation of hydraulic fracture in elastic rocks has widely been investigated. In the paper, we shall focus on numerical modeling of hydraulic fracturing in a class of porous rocks exhibiting plastic deformation. The plastic strain of porous rocks is described by a non-associated plastic model based on Drucker–Prager criterion. The plastic deformation is coupled with fluid pressure evolution described by the lubrication theory. An extended finite element method is used for modeling the propagation of fracture. The fracture propagation criterion is based on the J-integral. The proposed numerical model is validated by comparisons with numerical and analytical results. The influence of plastic deformation on fracture propagation process is investigated.
The phenomenon of moisture increase under an impervious cover in soils due to thermal gradients is defined as the pot cover effect, which may lead to an obvious soil moisture increase in the shallow soil. This paper explores a measure of laying an impervious layer at an appropriate depth in the process of foundation treatment to eliminate the potential moisture increase in the covered soil. Because the impervious cover above the soil and the impervious layer inside the soil constitute a “double pot cover” structure, the moisture migration in the covered soil with an impervious layer is generalized as the double pot cover effect. To investigate the mechanism of the double pot cover effect and further determine the optimal depth of the impervious layer, a numerical model is established to simulate this problem. Analysis results indicate that the moisture increase under the cover varies with the depth of the impervious layer. As the impervious layer is laid at a certain depth, the moisture increase reaches a minimum value. Moreover, the double pot cover effect under different boundary temperatures is further discussed. Results show that the moisture increase in the covered soil can be significantly reduced by laying the impervious layer slightly below the freezing front (0 °C).
The problem of the dynamic responses of a semi‐infinite unsaturated poroelastic medium subjected to a moving rectangular load is investigated analytical/numerically. The dynamic governing equations are obtained with consideration of the compressibility of solid grain and pore fluid, inertial coupling, and viscous drag as well as capillary pressure in the unsaturated soil, and they can be easily degraded to the complete Biot's theory. Using the Fourier transform, the general solution for the equations is derived in the transformed domain, and then a corresponding boundary value problem is formulated. By introducing fast Fourier transform algorithm, the unsaturated soil vertical displacements, effective stresses, and pore pressures induced by moving load are computed, and some of the calculated results are compared with those for the degenerated solution of saturated soils and confirmed. The influences of the saturation, the load speed, and excitation frequency on the response of the unsaturated half‐space soil are investigated. The numerical results reveal that the effects of these parameters on the dynamic response of the unsaturated soil are significant. 相似文献