In this study, a total of 30 clayley soil samples have been collected from various locations in Miri. A number of tests have been conducted including the determination of index properties, moisture content and shear strength. From the data obtained, a few relationships between the physical and mechanical properties were established. An empirical formula for the relationship between liquidity index and undrained shear strength is presented as Cu=95.724e^-4.180912.  This makes it possible for an evaluation of the shear strength of clayley soils by using their liquidity index value. It has been experimentally verified that the plasticity index of soils can be defined as a range of water contents producing a 66-fold variation in undrained shear strength. This has led to the establishment of the plastic limit as the water content at which undrained shear strength is around 95.7kN/m2. Undrained shear strength of a soil at the liquid limit can be considered to be around 1.42kN/m2.