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Title: The stress-strain pore-pressure relationship of normally-consolidated clays
Author: Lo, Kwan Yee
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1966
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Current theories of stress-strain relationship of clays are reviewed and their inadequacies discussed. In the existing methods of predicting pore pressures, pore pressures are invariably considered as some functions of applied stresses. These "stress theories" are generalized, examined, and found to be incompatible with several important experimental observations on undisturbed clays. It is shown mathematically that the pore pressure induced by shear may be expressed as a sole function of major principal strain, obliterating the anomalies inherent in the "stress theories". Using the mechanical behaviour of contiguous particles and current ideas of the physico-chemical properties of clays as the framework, a qualitative concept is developed to explain the stress-strain-pore pressure inter-relationships of normally-consolidated clays. Different types of undrained triaxial tests were performed on various undisturbed clays. Analysis of these test results and of those published in the literature, shows that the above concept is versatile in the interpretation of experimental data, and useful in unifying the diverse observations into a self-consistent phenomenon. A unique relationship exists between the pore pressure ratio ∆us/p (where ∆us is the pore pressure induced by shear and p the consolidation pressure) and the major principal strain for a given mode of consolidation. This relationship is independent of: (a) the direction of the applied stress path, (b) time of sustained stress, (c) magnitude of consolidation pressure, (d) time of consolidation, (e) applied stress system during shear, and (f) anisotropy. Factors which may affect the maximum pore pressure ratio and principal effective stress ratio are also studied. The plausibility of extension of this work to overconsolidated clays is expounded. Some current concepts of the shear behaviour of clays are correlated with the writer's approach, and their limitations and validities defined. Applications of the theory to field problems have been presented elsewhere
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available