摘要：AbstractStrength of subgrade affects the thickness of pavement layers placed over it. Stronger subgrade results in reduction in design thickness of the pavement layers placed over the subgrade. For a given project site, the existing subgrade may not always be strong, hence may require upgradation in terms of improvement of strength. On the other hand, due to rapid industrialization throughout the world, large amount of waste materials are generated. This creates environmental hazard. So utilization of waste materials as an additive to poor subgrade soil can be a feasible solution. It will help to utilize those materials by reducing the environmental pollution. Additionally, geogrid mesh may be introduced in the soil to increase the strength of the poor soil. The present study was undertaken with this objective. In the experimental study, Soil (S) is collected from nearby field of Bengal Engineering and Science University (BESU), Shibpur campus which is mainly silty clay. This soil is mixed with the waste material i.e. pondash (P) and rice husk ash (R). Lime (L) is added as an admixture. The mix composition ratios are taken as S: P (2:3), S: R (5:1 and 4:1), S: P: R (10:15:2) and S: P: L (50:75:1, 50:75:2, 50:75:3). The unsoaked and soaked California bearing ratio (CBR) values are of these mixes are observed to increase by 1.16 to 2.06 times and 1.22 to 3.72 times respectively with respect to the parent soil. Further, for attaining better strength geogrids are inserted at half and one-third height (both from top and bottom of the sample) of the mould. The unsoaked CBR values did not show any significant change but the soaked CBR value showed substantial increase. The unsoaked and soaked CBR value of S: P (2:3) is increased by 1.44 and 1.08 times than parent soil for the inserted geogrid at the half height of mould. From the soaked CBR value, S: P: R (10:15:2) and S: P: L (50:75:1) are preferred mix after inserting the geogrid at one third of height (at two places).
