Browsing by Author "Maregesi, Gerald Roosevelt"

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    Development of mathematical model for computing plastic limit from liquid limit cone penetrometer flow curve
    (University of Dar es Salaam, 2007) Maregesi, Gerald Roosevelt
    The current plastic limit determination is a very subjective test. A pert from the fact that test is standardized in AASHTO T90-94, ASTM and BS 1377: Part 2, the testing procedure is still very subjective. The test result depends largely on the operator`s judgments on the crumbling moisture content of the soil and diameter of soil thread. In this dissertation, conceptualized mathematical model which defines the liquid limit cone penetrometer flowcurve up to zero moisture content has been developed. The developed models were calibrated and validated using 185 Atterberg limit test results collected from various site laboratories and the accuracy of the model was found to be within the reproducibility range given in AASHTO T90-94 (85% of the results were within the range). The develop mathematical models gives unique opportunity for computing/ predicting the cone penetration of the soil even at very low moisture content at which, due to practical limitation it is impossible to determine the soil penetration. Furthermore, it was established that sometime the soil thread, but in actual fact the soil possesses some plasticity but can not be quantified by the conventional method of determining the plastic limit. It has been proved that in most cases the soil is classified as non plastic when its actual plasticity index is within the range of #10.