NEHRP Clearinghouse
- Title
- NGI (Norwegian Geotechnical Institute) Direct Simple Shear Tests on Concord Blue Clay.
- File
- PB80209810.pdf
- Author(s)
- Kopal, D. J.; Zimmie, T. F.
- Source
- National Science Foundation, Washington, DC. Engineering and Applied Science., December 1979, 108 p.
- Abstract
- A laboratory study investigated the dynamic behavior of clay soils on an effective stress basis. Emphasis was placed on high strain cyclic loading that occurs during earthquakes and storm wave loads. A direct simple shear device of the Norwegian Geotechnical Institute (NGI) was used to test the consolidated constant volume static and cyclic strength characteristics. Laboratory tests were conducted on Concord Blue Clay having two different consolidation histories (consolidation refers to the application of vertical normal stress to the soil sample). The first set of tests cyclically loaded normally consolidated clay and the second set cyclically loaded over-consolidated clay. Stress-controlled cyclic tests conducted to maintain constant cyclic shear levels measured lateral shear strains and effective vertical stresses as a function of the number of loading cycles. Static load tests provided a comparison with cyclic loading tests. It was demonstrated that clay strength degradation can be affected by cyclic shear stress levels, effective stresses, consolidation ratios, and number of loading cycles. Clay degradation was examined by employing the Ramberg-Osgood model. A correlation between experimental and mathematical modeling results was developed to determine the accuracy of the Ramberg-Osgood model. A literature review, equipment descriptions, testing procedures, and test results are included.
- Keywords
- Shear properties; Dynamic response; Earthquake engineering; Clays; Concord blue clay; Shear tests; Soil properties; Cyclic loads; Soil mechanics; Earthquakes