Permanent Deformation Approach

The principal limitation of Wright s static displacement model is that it does not consider the accumulation of deformations due to the passage of a number of waves. This problem has been approached by Schapery and Dunlap (1978), modeling the soil as a linearly viscoelastic material. Their analysis also included the effect of energy adsorption of the seafloor on the wave characteristics. 

Lee (1974) developed a more rigorous method of estimating the permanent deformations experienced by earth structures during a dynamic loading. This method followed the basic Seed approach for calculating the F.S. and strain potential for individual elements (Seed, 1966). Differences between the two methods depend on procedures used to calculate deformations from the strain potential values. 

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Evidently a fluid polymer cannot be considered in the model the deformation approaches to a limit. For a solid polymer the model seems more appropriate, though is represents neither a spontaneous elastic deformation nor permanent flow. Therefore a combination of a Kelvin-Voigt element with a spring and with a dashpot in series is, in principle, more appropriate. 

The question of whether plastic strain is truly permanent, or merely a feature of very slow recovery processes has yet to be settled. The integral equation approach has confirmed that the existence of true stress maxima does not necessarily imply permanent deformation although... 

Another common theory was proposed by Manson (27) and is referred to as the universal slopes equation. In this model, the plastic strain or permanent deformation, is considered as a measure of the damage imposed in the material. On this basis, the true plastic strain amplitude can be used as a measure of the fatigue behavior. Moreover, the fatigue curve can be predicted in terms of the monotonic stress-strain curve. This empirical approach was initially statistically correlated with many metals and takes the following form ... 

Elastomeric systems are one of the most important classes of materials in industry because of their specific dynamic properties. Elastomers are typically crosslinked to a greater or less degree in order to improve their properties. The crosslinking process termed vulcanization prevents permanent deformation under load and ensures elastic recovery on removal of the load. The introduction of crosslinking, however, limits the ability to characterize those systems because of the insolubility of the resulting network. Additionally, the extremely low concentration of the chemically modified structures induced by the vulcanization challenge many of the traditional analytical techniques. Many approaches including physical tests and chemical analysis have... 

We note that the Voigt model predicts that strain is not a continuous function of stress that is, the element does not deform continuously with the sustained application of a constant stress. The strain approaches an asymptomatic value given by (Oq/E). The strain of the element at equilibrium is simply that of an ideal elastic solid. The only difference is that the element does not assume this strain instantaneously, but approaches it gradually. The element is shown to exhibit retarded elasticity. In creep recovery, the Maxwell element retracts instantaneously but not completely, whereas the Voigt element exhibits retarded elastic recovery, but there is no permanent set. 

Adverse local conditions, such as great level difference vast areas of woodlands, limited possibilities of permanent observations due to the lack of power supply, especially in winter and also specific character of the objects require individual approach to the organization of studies. The experience gained in the field during the studies conducted in the Polish and Czech Sudetes (Cacoh et al., 1987,1989, Kostak and Cacon, 1988) has resulted in working out a survey system and geometrical analysis and interpretation of rock deformations (stiff blocks). 

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