Effects of Capillary Rise Saturation on Properties of Sub Grade Soil

Abstract

Design of the pavement layer to be laid over the subgrade soil can start with the estimation of subgrade strength or capacity and the volume of traffic to be carried. Various pavement layers are very much dependent on the strength of subgrade soil over which they are going to be laid. The subgrade soil can be subjected to change in moisture or saturation level due to capillary rise/saturation (h_c). The hydraulic conductivity of subgrade soil can be strongly dependent on the texture (contents), grain size, densities and voids of the soil. Change in moisture level in subgrade soil causes change in subgrade properties, strength or capacity and it can be quite essential for engineers to understand the effects of capillary rise on the variation of moisture in subgrade soil and effects on the strength properties. The strength properties of subgrade soil is mostly expressed in terms of CBR (California Bearing Ratio) and understanding the dependence of the CBR strength of subgrade soil on water content (moisture variation) will contribute better towards the design and maintenance practices. The strength of subgrade soil may vary largely on the amount of saturation in it, i.e. the amount of water exposed in the subgrade soil. Hence in this research an attempt has been made are to determine or estimate hydraulic conductivity of the subgrade soil at varies densities, Saturation level due to capillary rise/height at varies degree of soaking (time of saturation) from day (0) to day (4) and study the effects of capillary saturation on the properties of subgrade soil, including CBR at different level of saturation through the purposive sampling in each five stations. It observed that for each four stations subgrade soils, the strength properties reduced, i.e. the CBR values reduced from the un soaked condition to soaked condition. For sample 1 subgrade soils, the CBR values reduced by 82% to the un soaked condition or no change in moisture and provide a subgrade soil with non-susceptible to hydraulic conductivity which can reduces flow of water through them.