Predicting the value of CBR from DCP for Addis Ababa Red clay
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Date
2014-11
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Addis Ababa University
Abstract
The research attempts to introduce the Dynamic cone penetration (DCP) to replace CBR test in preliminary design stage. DCP is a simple test device, portable and easy to operate and a repeated test can be conducted as much as desired to achieve a better and reliable design parameter.
Field DCP test with in situ density test were conducted. Disturbed and undisturbed samples were taken to the laboratory with which natural moisture content, Atterberg limits, grain size analysis, free swell, standard proctor density test and CBR were conducted.
After looking thoroughly the scatter diagrams, it is found out that DCPI is influenced by in situ moisture content and bulk density however it is not influenced by Atterbeg limits. It is also found out that there is good relationship between DCPI and CBR.
Different techniques are used to find an expression that best suits to find the value of CBR from DCP and other parameters. The final accepted one is the expression developed by using two stage residual inclusion estimation using liquidity index as variable The result gives the following equation with N=36 and adjusted coefficient of determination of 0.633.Predicted DCPI=0.207*LI + 22.571
CBR=-0.142*DCPI-0.18(DCPI-Predicted DCPI) +7.701
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Keywords
Addis Ababa Red clay, CBR, DCP