Determining correlation between CBR, UCS and Triaxial test value of different subgrade soils

Abstract

Efficient transportation network is essential for safe, timely and economic conveyance of goods and
passenger. In this regard’s highway construction is very important activity for development of any region.
Different types of vehicles are moving on the same right of way of highway section. The design of pavement
section is mainly depending on repetition of heavy loaded vehicles like, trucks (single axle& multi axle). The
overall thickness of pavement section also depends on strength of subgrade soil. IRC recommended California
bearing ratio (CBR) test for subgrade soiling flexible pavement design CBR gives a penetration resistance value of
subgrade soil.
Which represents indirectly shear strength of soil but this test is time consuming. However rutting failure in sub
grade soil is due to excessive shear strain under wheel load. Hence evaluation of shear strength of sub grade soil is
necessary for different moisture contents. This strength of sub grade soil may be obtained for unconfined i.e. for
only axial loading and for confined i.e. for axial loading with lateral a fining pressure, means triaxial loading. The
unconfined compressive strength (UCS) test of subgrade soil is one of the fastest and cheapest methods of
measuring shear strength. Whereas triaxial testing determine modulus of deformation from stress-strain curves.
This test also determines the required thickness of pavement layers. It is interesting to know whether there is any
relation between CBR value, UCS value and Triaxial test value or not. Looking at the above this study is aimed to
determine correlation between CBR (California bearing ratio) value, UCS (unconfined compressive strength)
value and Triaxial test value on different types of soils available near by the Himmatanagar laboratory
investigations will be carryout for the individual soil types and for the combination(mixing) of different soils. This
relationship may be useful to estimate the CBR value &triaxial test value from the UCS (unconfined compressive
strength) value of given soil sample.