Effect of the Grain Size of Sand on Expansive Soil

Abstract

The interest in expansive soils goes as far as they were considered as a new phase of soil mechanics. Problems associated with potential volume change of soils occur worldwide, mainly in the arid and semi-arid climatic region, as is the case of the country of this research. These problems are particularly existed in regions where the variation in the moisture content can cause a potential expansiveness of the soil. In fact, Bentonite/Sand mixture represents one of the available answers for the geotechnical engineering problems such as heaves, cracks and other damages caused by swelling and shrinkage. This mixture may be used to 1) reduce the settlement time of structures, and 2) increase the permeability of soils. The main target of the present work is to demonstrate the influence of adding sand on an expansive soil (bentonite) behavior. This includes an investigation to the effect of the amount and the particles size of sand on the physical properties of the expansive soil. The reduction in swelling and swelling pressure of the expansive soil by the addition of different percentages and different particles size of sand and the consequent effect on strength characteristic were also studied. Thirteen samples of Bentonite/sand mixture were used in this study to evaluate the effect of the sand percentages on the swelling behavior. To implement the laboratory program, many tests were used which were sieve analysis, Atterberg’s limits, compaction, and free swelling test with swelling pressure test. The results indicated a reduction in the liquid limit of around 55% and in the plastic limit of around 54%, where the increase in the maximum dry density was 46%. On the other hand, the reduction in the swelling pressure was 87.5%.