The Effect of Relative Density and Confining Stress on Shear Properties of Sands with Varying Grading |
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| Authors: | Ogbonnaya Igwe Hiroshi Fukuoka Kyoji Sassa |
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| Institution: | 1. Department of Geology, Faculty of Physical Sciences, University of Nigeria, Nsukka, Enugu State, Nigeria
2. Research Centre on Landslides, Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan
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| Abstract: | The research investigated the influence of grain size distribution on the shear behavior of sand specimen in loose, medium and dense states. The investigation aimed at understanding the extent or degree at which static shear strength of soil is affected by its density. A standard indicator (coefficient of uniformity) was used in constituting four (4) different sand specimens—narrowly graded (NAG), intermediately graded (ING), well graded (WG) and gap graded (GAG). Different normal stress values were applied during the testing program. The specimens were sheared using a ring shear apparatus until a residual value of shear stress was obtained. Result obtained from the analysis shows two remarkable stress paths. Medium dense to dense specimens show dilative stress path while loose (less dense) specimens show contractive stress path. At loose state, WG specimens show higher peak and residual shear strengths than poorly graded ones. Of importance was the fact that all the NAG specimens underwent complete liquefaction but WG specimens did not undergo complete liquefaction. This was interpreted as strong inter-particle contacts/forces binding the grains which enhanced high shear resistance. The research also showed that increase in relative density leads to higher shear strength, particle size distribution notwithstanding. Also, result of the analysis showed that WG specimens in medium-and dense states have higher peak but lower residual strength than ING and NAG specimens-this phenomenon was termed reverse behavior by the author(s). GAG specimens when sheared have the lowest peak and residual strength at any given value of relative density. |
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