Meaning, measurement, and practical application of swelling pressure
Pakbaz, Mohammad Cyrus
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Permalink
https://hdl.handle.net/2142/19456
Description
Title
Meaning, measurement, and practical application of swelling pressure
Author(s)
Pakbaz, Mohammad Cyrus
Issue Date
1991
Doctoral Committee Chair(s)
Mesri, Gholamreza
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Language
eng
Abstract
Magnitude of swelling pressure and time-rate of swelling pressure development for Taylor shale material were investigated. A total of 227, 2.5 inch and 1.77 inch diameter Taylor shale specimens oriented both perpendicular as well as parallel to the bedding planes were tested in three types of loading frames, using four different methods of measurement of swelling pressure. A number of specimens were also tested after they were exposed to different drying environment in order to broaden the understanding of magnitude of swelling pressure and time-rate of swelling pressure development. Taylor shale material tested included M-1 Taylor shale with natural water content of 12 to 16% and plasticity index of 24 to 43%, M-0 Taylor shale with natural water content of 19 to 43% and plasticity index of 49 to 203%, and weathered Taylor shale with natural water content of 14 to 34% and plasticity index of 40 to 70%.
It has been determined that swelling pressure of Taylor shale at specimen void ratio, $\sigma\sb{si}$, is directly related to swelling index and indirectly related to degree of fissuration of shale specimen. Furthermore, swelling pressure of Taylor shale specimen is found to be directly related to modulus of deformation of specimen. The effect of method of measurement on the magnitude of swelling pressure of Taylor shale material has been also established.
Time-rate of swelling pressure development of Taylor shale has been determined to be influenced by the presence of micro-fissures. The study also included development of methods for predicting mobilized swelling pressure and time-rate of mobilized swelling pressure development around a circular tunnel and investigation of factors which affect the magnitude of mobilized swelling pressure and time-rate of mobilized swelling pressure development. The solution of predicting time-rate of swelling pressure development around a circular tunnel developed in this study seems to agree well with an actual case in London clay.
An important factor which determines the magnitude of mobilized swelling pressure in the field is undrained deformations that occur due to an excavation as a result of opening of fissures and joints. In spite of the limitation of the analysis and the assumption that are made in predicting undrained strains both in the laboratory and in the field, it seems that Taylor shale specimens have been subjected to the same degree of fissuration as the shale mass around a tunnel. This implies that magnitude of swelling pressure in the field is expected to be similar to that measured in the laboratory at specimen void ratio.
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