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Guided circumferential waves in layered poroelastic cylinders

Shah S. A., Apsar G.

International Journal of Applied Mechanics and Engineering

2016

Vol. 21, no. 4

933--950

The present paper investigates the propagation of time harmonic circumferential waves in a two-dimensional hollow poroelastic cylinder with an inner shaft (shaft-bearing assembly). The hollow poroelastic cylinder and inner shaft are assumed to be infinite in axial direction. The outer surface of the cylinder is stress free and at the interface, between the inner shaft and the outer cylinder, it is assumed to be free sliding and the interfacial shear stresses are zero, also the normal stress and radial displacements are continuous. The frequency equation of guided circumferential waves for a permeable and an impermeable surface is obtained. When the angular wave number vanish the frequency equation of guided circumferential waves for a permeable and an impermeable surface degenerates and the dilatational and shear waves are uncoupled. Shear waves are independent of the nature of surface. The frequency equation of a permeable and an impermeable surface for bore-piston assembly is obtained as a particular case of the model under consideration when the outer radius of the hollow poroelastic cylinder tends to infinity. Results of previous studies are obtained as a particular case of the present study. Nondimensional frequency as a function of wave number is presented graphically for two types of models and discussed. Numerical results show that, in general, the first modes are linear for permeable and impermeable surfaces and the frequency of a permeable surface is more than that of an impermeable surface.

Evaluation of soil permeability from consolidation analysis based on Terzaghi’s and Biot’s theory

Dobak P., Gaszyński J.

Geological Quarterly

2015

Vol. 59, No. 2

373--381

Proper evaluation of permeability parameters has a crucial signification in multi-scale prediction of consolidation. Drainage path is connected with the time of one-dimensional consolidation in Terzaghi’s theory and numerous later solutions. That is why the evaluation of permeability factor allows to model the settlement’s time of geological layers based on results obtained on a laboratory scale. Numerous tests show a difference of the consolidation degree obtained from one-dimensional strain course and pore pressure distribution. Evaluation of consolidation coefficient cv based on a newly proposed method allows better understanding of the basic reasons of unconventional behaviour of tested soils. Unparallel characteristics of strain and pore pressure distribution show important role of soil’s skeleton creep and its relation to permeability aspects. Solutions proposed by Biot’s theory allow analysing the different velocity of strain and pore pressure distribution. The article presents a new approximated method based on Terzaghi’s theory and evaluation of parameters which are necessary in application of Biot’s one–dimensional solution. These parameters are connected with compressibility and coefficient of permeability. The goal of presented methodological studies is comparison between permeability obtained from application of Terzaghi’s and Biot’s theory. It allows trying to explain physical reasons of differences between applied models and testing results, and improving the methodology of one–dimensional consolidations tests.