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Research project on Atterberg limits using Casagrande and fall cone methods


Students conduct Atterberg limits tests, liquid and plastic limits, on the same soil using two types of techniques; (1) Casagrande apparatus (commonly used in the U.S.) and (2) fall cone apparatus (used in Europe and Asia). The students share data from all groups (typically 10) and analyze in ways of their choice. They are graded based on the quality and depth of their analyses (e.g. statistical analysis on repeatability of results, is one method better than the other, operator dependence) and written quality of their technical paper. The project is worth 5 percent of the total course grade.

The purpose of this exercise, other than obtaining a greater knowledge of test methods and the Atterberg limits, is to understand that test results should not be accepted blindly. Traditional laboratory exercises on this subject have students obtain liquid and plastic limits for the purpose of soil classification. The tests are performed once, and the limits are taken by the students as absolute values without regard for the possibility of operator or experimental error. This traditional laboratory exercise is still done in the beginning of the semester with the research project as a follow-up project. This shows students that there are multiple methods for obtaining the limits, and that care should be taken in following experimental standards (e.g. ASTM) to obtain accurate and repeatable results. Most importantly, this exercise brings students through the process of collecting multiple sets of data, analyzing and presenting the data, as well as discussing and concluding meaning from the data. The project is relatively simple to conduct, so additional time can be devoted to writing the research paper in the ASCE conference format, which takes time because students find it quite different than writing a traditional laboratory report.

   


Last modified June 11 2010 04:39 PM

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