COMPARISON OF CBR AND DCPI CORRELATIONS ON SOILS USING ASTM

Abstract

California Bearing Ratio (CBR) plays a pivotal role in the design of flexible pavement as it
indicates the strength of pavement subgrade material and decides pavement thickness. It is
cumbersome to evaluate CBR value proximately every time. Development of correlations
between CBR and Dynamic Cone Penetration Index (DCPI) on soils will ease the testing work of
highway design engineers in evaluation of subgrade CBR value. Research is being in
progression to test the reliability of this correlation. The present study is focused to bring out the
reliability of CBR and DCPI correlation on Indian soils such as black cotton soils and murrum
soils. The correlations published in ASTM-D-6951 were considered for comparison of the test
results. Dynamic cone penetrometer tests were conducted for three different soils like black
cotton soil, murrum and sandy soil along with laboratory CBR tests. A comparison study is made
between laboratory CBR and CBR values obtained from the DCPI value and also, between CBR
values obtained by using the correlations published in ASTM D 6951. Percentage reduction in
CBR value obtained from ASTM is compared with that of laboratory CBR value. The percentage
change in CBR of clay showed more compared to the granular soils. The correlations developed
are verified and proposed for sustainable engineering practice point of view.