physical specifications and mechanical behavior of swelling gypsiferous soils

swelling soils which are outspread all over the world cause irrecoverable damages to buildings. this type of problematic soils exits in south west of mashhad and seems to be the main reason of some damages including cracks in buildings and pavements. the soil profile in this region is mainly gypsum and fine which can be classified as…sm and cl. however, in some parts course aggregates are observed. the present research is an attempt to identify the characteristics and swelling property of gypsum soil of this region. to examine this issue, 10 samples containing different gypsum percent were taken from various places in this region. the geotechnical properties of the samples including gypsum content, atterberg limits, natural unit weight, dry unit weight and density were investigated. the influence of gypsum amount on swelling potential was then studied. all samples were moulded with identical moisture content and unit weight. the impacts of some other factors such as compaction and cycles of dry and wetting on swelling potential were also investigated.the results of the present research indicate with increasing gypsum content and degree of compaction, swelling potential increases rapidly. it is also shown that with increasing number of cycles the magnitude of maximum swelling potential increases so that after a few cycles remains mainly constant.