Coefficient of permeability of treated soils

Abstract

Effects of lime and fly ash content on the permeability of treated soils were investigated. Two types of soils (clay with low plasticity and fine sand) were selected. One of the samples was collected from Porsha of Rajshahi (clay) and other one was collected from Mirpur of Dhaka (fine sand). After collecting these soil-mass from the field, they were dried and cleaned. Samples were prepared by mixing additives with a percentage of 1%, 3% and 5% (by weight). Water was mixed with it for reaction to occur and then a sufficient time was allowed to complete hydration. Afterwards, the sample was subjected to permeability test. Permeability of sandy soils was determined by performing constant head permeability tests on the respective samples, while for clay soil falling head permeability tests were performed. Index tests indicated that plastic limit increased with increasing lime content and fly ash content while liquid limit and plasticity index reduced with the increase in lime content and fly ash content. The results are in agreement with those reported in Ahmed (1984) and IRC (1976). In the research scheme, lime and fly ash content was varied up to 5% and the reaction time was varied up to 14 days, i.e., after mixing a particular soil with a definite percent of lime, fly ash and sufficient water, the mixture was allowed for complete hydration at room temperature for 3, 7 and 14 days before testing. Test results show that decrease of permeability for both sandy and clayey soil with the increase of lime and fly ash content. Void ratio of treated soil was influenced by the addition of lime and fly ash content. For soils having substantial amount of fines were observed that void ratio decreased with the increase of lime and fly ash content. The permeability characteristic also changed accordingly. Aging had no affect on the permeability and void ratio of untreated soils. But the void ratio and hence permeability of lime and fly ash treated soil were slightly changed with the reaction time.