Evaluation of Swelling Control Parameters for Stabilized Expansive Soil Buffer Layers under Pavement Embankment

Abstract

Flexible Pavements constructed on expansive soils like Black Cotton (B.C.) soils, suffer extensive damages due to volume changes and the resulting swelling pressures. The magnitude of the swelling pressure depends on various parameters but the moisture content variation which occurs during different seasons is the major cause of volume changes. To control this moisture variation, present study suggests to lay a lime stabilized buffer layer below the road embankment. This layer will be underlain by a mechanically stabilized layer with vertical cut-offs on either side. For the success of this methodology, it is necessary that, the swelling pressures of the stabilized layers of B.C. soil should be first lowered. The success of this protective methodology will also be depending upon the of moisture content at which these layers are to be compacted and also on the estimation of optimum percentage of lime to be used for stabilization. A combination of measures can be used to minimize the replacement of BC soil and its resulting impact on overlying structures especially pavements. The aim of the present work is to study these two parameters. Subsequently these properties will be used in recommending a combination of measures to minimize detrimental effects on overlying flexible pavements. Therefore, it is necessary to find out the relation between swelling pressure and those standard reference moisture contents such as Shrinkage Limit (SL) and Optimum Moisture Content (OMC) which being the properties of any given soil, will not vary with time. In the present study, therefore, SL and OMC are considered as the reference moisture contents for the soil and the variation in swelling pressures of the soil is studied at SL, OMC-2%, OMC and OMC+2%. The present study also, attempts to find out the possibility of using Shrinkage Limit value as a parameter in finding the optimum percentage of lime. X-Ray Diffraction tests were also carried out to study the effect of mineralogy on the observed swelling behaviour of the soils.