T. S. Nagaraj

Prediction of the Preconsolidation Pressure and Recompression Index of Soils

Based on the generalized compressibility equation a procedure is given to estimate the preconsolidation pressure and the recompression index of stress and time dependent overconsolidated soils. This is based on knowledge of (1) the in-situ void ratio, (2) the liquid limit of the soil, (3) the in-situ overburden pressure, and (4) the specific gravity of the soil solids. Estimates of these consolidation parameters, which often are sufficiently accurate, can be obtained without carrying out consolidation tests. The estimated values for specific soils are compared with published data.

Liquid Limit Determination—Further Simplified

In recent years the cone penetration method to determine liquid limit of soils has gained popularity and acceptance. This paper advances two more specific potentials of this method by which (1) the liquid limit can be determined almost instantaneously and (2) the liquid limit of soils, also having particles coarser than 425 µm can be directly determined. The interrelation between water content and bulk density at known degree of saturation and specific gravity of soil solids has been used to compute the water content. In the cone penetrometer method, availability of a cup of standard volume is shown to be helpful in determining the bulk density of the soil for different penetration values. In the range of water contents around liquid limit it is further shown that the degree of saturation of the bulk soil in the cup is around 98%. Using this, the water content at different penetrations can be computed. The floating matrix concept has been used to demonstrate the ability of this method to determine the liquid limit of soils also having particles coarser than 425 µm. The limiting size and percent of coarse particles have been indicated.