رفتار خاك هاي گچي و اثرات سيكل هاي تر و خشك شدن و بارگذاري و باربرداري بر خواص آنها

Mechanical Behavior of Gypsum Soils and the Effects of Cycles of Wetting and Drying and Cycles of Loading and Unloading on their Properties

The soils, when saturated, swell or settle are referred as problematic soils. Due to the complicated behavior, such these soils damage to the structures. Gypsum soils are generally porous due to the presence of gypsum and apply huge settlement, in proportion w ith degree of porosity, to the structures. The present research is an effort to identify the soils of South East of Mashhad city, which naturally contain relatively high gypsum and have a special behavior. In this regard, so many samples with different magnitudes of gypsum were gathered and classified to seven samples with different magnitudes of gypsum. Preliminary tests reveal that with increasing of gypsum, plasticity index and unit weight decrease, which in turn increase settlement. In order to investigate the influence of degree of compaction, all samples were compacted with different unit weight and the swelling potential and swelling pressure were measured after saturation. The results show that with increasing unit weight and gypsum, swelling potential increases. Cycles of wetting and drying and also cycles of loading and unloading were performed to investigate their influence on gypsum soils.