BEHAVIOUR OF OVER CONSOLIDATED CLAYS

Abstract

The determination of the in situ over consolidation ratio (OCR = ratio of preconsolidation pressure to effective overburden stress) of clays from standard one-dimensional CONSOLIDATION tests is not always straightforward. An alternative and independent evaluation of the OCR can be made from the results of laboratory strength tests, in particular undrained triaxial (CIU/CAU). In the present paper an attempt has been made to study the over consolidation behaviour in Lab. by conducting triaxial undrained test, i.e. CIU-isotropically consolidated undrained test and Direct simple shear (DSS) test. In this investigation, efforts have been made to simulate the in situ conditions in the Laboratory for the two clayey soils viz. Dhanauri clay and Yamuna clay. The tests have been carried out on the remoulded samples, which were prepared at optimum moisture content. A number of samples were tested to know their index and engineering properties. Detailed results of the various properties are given in the main text. Studies show that in addition to undrained strength, the OCR affects the lateral stress coefficient (Ko), soil modulus (E), pore pressure parameter at failure (Af), low strain shear modulus (G), coefficient of consolidation (Cu) etc. This study has been useful and enlightening for the author who hopes that it will be useful to others and will make some contribution to the application of over consolidated soils in this country.