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Browsing University of Delaware Open Access Articles by Subject "Clays"
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Item Measuring "Fast" Shear Strengths Along Slickensided Surfaces in the Bromhead Ring Shear(ASTM International, 2008) Meehan, Christopher L.; Brandon, Thomas L.; Duncan, J. M. (James Michael); Meehan, C. L., Brandon, T. L., Duncan, J. M.; Meehan, Christopher L. (orcid.org/0000-0002-9721-6275)Fast and slow ring shear tests were performed in the Bromhead ring shear device to examine the effect of the displacement rate on the shear strength measured along slickensided discontinuities in Rancho Solano Fat Clay. For each test, initial drained shearing was performed at a displacement rate of 0.018 mm/min, fast shearing was performed at a rate of 44.5 mm/min, and drained shearing was recommenced at a displacement rate of 0:018 mm/min. Significant variations in measured post-peak shear strengths were observed, and problems with the pore pressure response in the soil surrounding the slickensided plane are discussed. As a result of these problems, it was concluded that fast Bromhead ring shear tests may not be suitable for evaluating the effects of fast shearing on the strengths of slickensided surfaces.Item Measuring Drained Residual Strengths in the Bromhead Ring Shear(ASTM International, 2007) Meehan, Christopher L.; Brandon, Thomas L.; Duncan, J. M. (James Michael); Meehan, C. L., Brandon, T. L., Duncan, J. M.; Meehan, Christopher L.(orcid.org/0000-0002-9721-6275)A series of Bromhead ring shear tests were conducted to measure the drained residual strength of Rancho Solano Fat Clay. Tests conducted using different test procedures demonstrate the significant effect that wall friction can have in the Bromhead ring shear device. This problem was addressed by beveling the top loading platen, which led to measurements of drained residual strength that were 21–23 % lower than those measured with the unmodified platen. Using the modified platen, similar test results can be achieved independent of the details of the test procedure that is followed, giving greater confidence in the measured residual shear strength.