A study of the effects of varying rates of loading on the consolidation of soil.
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Authors
White, Robert K.
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Advisors
Date of Issue
1959
Date
Publisher
Rensselaer Polytechnic Institute
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Abstract
In order to predict more accurately the settlement of structures, many approaches to the theory of consolidation have been made. The most famous of these is the Terzaghi theory. The limitations of this theory as associated with construction loading have been recognized by Schiffman in his approach to a mathematical solution. Marron initiated investigations into the validity of Schiffman's work, and it is the purpose of this investigation to further these studies. Testing was carried out on two types of apparatus. The first one, a standard, two-position static loading device, was utilized during three series of tests including a usual incremental test, a large incremental test, and a small incremental test. The second apparatus consisted of a Conbel loading device which was operated by air pressure regulated through a valve which in turn was connected to an opening mechanism. This opening mechanism consisted of a geared-down electric motor whose output rate could be varied by a belt-and-pulley arrangement to the valve stem. Thirteen test runs at varying rates were conducted with this device. Permeability readings were conducted throughout testing by use of a constant head permeameter developed by Marron. The material used throughout testing was a pure kaolinite clay, the inclusion of which it was hoped would eliminate many of the inconsistencies encountered in a natural soil. Thus, results would be that much more easily interpreted. The results of this experimentation show that there is a definite effect upon total strain and void ratio change by imposition of different loading conditions. It can definitely be seen that large increments and more rapid loading rates cause larger deformation. For the static tests it was seen that larger permeabilities were experienced at the same porosity when large increments were applied than when small increments were applied. During the time dependent loading tests, the results failed to show any definite relationship between permeability and porosity, though the fact that there was a spread of values leads to speculation that further, more intensive study along this line would be warranted. It is concluded that as far as the scope of this study has investigated, Schiffman's approach to the consolidation of soil under conditions of time-dependent loading and varying permeability is valid.
Type
Thesis
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Series/Report No
Department
Civil Engineering