The thermomechanical responses of a porous elastic medium subjected to time harmonic loads (normal force and thermal source) are investigated analytically in the context of generalised thermoelastic theory with one relaxation time. The material of the foundation, obeying Biot’s dynamic poroelastic theory, is idealised as a uniform, fully saturated poroelastic half-space stratum. The coupled governing equations are established based on Biot’s dynamic poroelastic theory and on generalised thermoelastic theory. Assuming the disturbances to be harmonically time dependent, the general solutions of stress, displacement, temperature distribution and excess pore water pressure are deduced using the Fourier transform, and the transformed solutions are numerically inverted. The differences among the coupled thermo-hydro-mechanical dynamic model (THMD), the hydro-mechanical dynamic model (HMD) and the thermo-elastic dynamic model (TMD) are discussed. In addition, the effects of the thermal loading frequency on the displacement, stress, temperature distribution and excess pore water pressure components are analysed in the numerical results. 相似文献
Vulnerability and resilience constitute different but overlapping research themes embraced by sustainability science. As practiced within this science, the two research themes appear to coalesce around one of the foundational pivots of sustainability, the coupled human–environment system. They differ in regard to their attention to two other pivots, environmental services and the tradeoffs of these services with human outcomes. In this essay I briefly review the emergence of sustainability science and the three foundational pivots relevant to vulnerability and resilience. I outline the distinctions and similarities between the two research themes foremost as practiced within sustainability science and especially in regard to the attention given to the three pivots. I conclude with the observation that improvement in the capacity of vulnerability and resilience research to inform sustainability science may hinge on their linkages in addressing tradeoffs. 相似文献
Eastward-propagating patterns in anomalous potential temperature and salinity of the Southern Ocean are analyzed in the output of a 1000-year simulation of the global coupled atmosphere–ocean GCM ECHO-G. Such features can be associated with the so-called Antarctic Circumpolar Wave (ACW). It is found that time–longitude diagrams that have traditionally been used to aid the visualization of the ACW are strongly influenced by the width of the bandpass time filtering. This is due to the masking of considerable low-frequency variability that occurs over a broad range of time scales. Frequency–wavenumber analysis of the ACW shows that the eastward-propagating waves do have preferred spectral peaks, but that both the period and wavenumber change erratically when comparing different centuries throughout the simulation. The variability of the ACW on a variety of time scales from interannual to centennial suggests that the waiting time for a sufficient observational record to determine the time scale of variability of the real world ACW (and the associated decadal time scale predictability of climate for southern landmasses) will be a very long one.Responsible Editor: Dirk Olbers 相似文献
Understanding of saline intrusion into coastal aquifer is an important issue in management and protection of groundwater resource,
which can be well achieved by groundwater modelling. To explain some phenomena of correlation between groundwater level and
salinity in observation wells in coastal area, the authors compare the migration velocity of saline particles and transmission
velocity of water pressure and derive analytical equations of these two velocities for plane and radial flows. The driving
force and resistance of saline intrusion were analysed based on the analytical modelling. The destruction and reconstruction
of the equilibrium between fresh water seepage towards sea and saline dispersion to inland were considered as an essence of
whole intrusion process. The dynamic process of seepage and dispersion at different stages of saline intrusion were analysed
under groundwater over-exploitation. The basic equations of saline intrusion were derived and the mechanism of transitional
zone movement was discussed. These constitute coupled seepage–dispersion theory of saline intrusion, which becomes an important
supplement to existing theory of saline intrusion. As a case study on saline intrusion in Guangrao County in Eastern China,
this theory was applied to predict the development of saline intrusion in the study area. 相似文献
If clays are subjected to flows of fluid, electrical charge, chemicals, or heat, in most cases, flows of different types occur simultaneously, even if only one driving force is acting. These are so-called coupled flows. Examples of coupling phenomena are streaming potential and electroosmosis, induced by the flows of fluid and electrical charge, respectively.
Since the 1960s, laboratory devices have been constructed to measure streaming potentials and/or electroosmosis in clays or clayey soils. Due to their mechanical and hydraulic properties, clays are not easy to work with. Consequently, laboratory devices have to deal with various complications. A new design for an experimental set-up is proposed. Contrary to earlier devices, the clay sample is mounted in a flexible wall permeameter, which avoids sidewall leakage caused by the possible swell or shrink of the clay. Gold-coated gauze electrodes completely cover the surfaces of the sample, which are in contact with the solution reservoirs that ensure one-dimensional flow. In addition, the thickness of the sample is monitored during the experiment. The chemical composition of the reservoir fluids is controlled during the experiment. The device is flexible with respect to changing the solutions of both reservoirs independently, applying different hydraulic gradients, and measuring or applying electrical potentials. Finally, it is possible to mount undisturbed clay samples in the set-up, keeping them in situ during the whole experiment.
With this set-up, an extensive program of measurements of coupling phenomena like streaming potentials, electroosmosis, and membrane potentials in a sodium montmorillonite is started. Preliminary results of streaming potential measurements are presented and demonstrate that the build-up of a streaming potential due to a hydraulic gradient is a reproducible process that influences the water flow through the clay, and that the extent of the streaming potential depends on the salt concentration of the permeating solution. 相似文献