Sid Nadukuru Article Published in Géotechnique
Sid Nadukuru (Georgia) co-authored an article entitled "Maturing of the contacts and ageing of silica sand" that was published in the journal Géotechnique on June 16, 2017.
In "Maturing of the contacts and ageing of silica sand," Sid discusses nominal inter-granular contact evolving. This contact causes ageing of silica sand. He also talks about the demonstration of micro-morphology of silica sand grains and how the process works. The tests conclusions were equivalent to the hypothesis.
Sid's co-authors were R. L. Michalowski, and Z. Wang.
AbstractA typical surface texture of silica sand grains is rich in asperities and mineral debris. Consequently, a nominal inter-granular contact is composed of many "contact points'. Associated with the contact loading process is micro-fracturing of the textural features, causing the contact to evolve. Even under a constant load, the process of micro-fracturing continues, although with a decreasing frequency. This static fatigue at contacts (or contact maturing) under a constant load is considered to be a major contributor to ageing of silica sand. The rich surface micro-morphology of silica sand grains is demonstrated using scanning electron microscopy and atomic force microscopy. Grain-scale tests indicate time-dependent deflection under constant load, attributed to delayed fracturing of textural features at grain contacts. The process is greatly dependent on the initial roughness of the surfaces. The rate of the deflection for a grain with large initial roughness (root mean square of grain surface elevation (RMS) = 621 nm), loaded with 2·4 N, was found to be 17·6 nm/h at the end of the first day after loading, whereas for a grain with approximately half the initial roughness (RMS = 321 nm) it was only about 2 nm/h. A consequence of the contact maturing process in grain assemblies is a time-dependent increase in macroscopic stiffness, and a resulting alteration of the stress state in a confined sand. This was confirmed in soft-ring oedometer tests on specimens subjected to constant load. The temporal scale of the radial stress increase in the oedometric samples was about the same as that in convergence tests on single grains. Contact maturing is accelerated by the presence of moisture and pressure dissolution, and this was manifested in tests on samples saturated with pore fluid. The results of both grain-scale and sand specimen tests are consistent with the hypothesis indicating contact maturing as the major contributor to time-dependent effects in silica sand.
For more information regarding the paper, visit: https://doi.org/10.1680/jgeot.16.P.321.
To learn more about Sid see his profile at: https://www.linkedin.com/in/nadukurus/.