Settlement and Collapse of Gypseous Soils

The work in this research presents an experimental, theoretical and field study in order to investigate the settlement of Gypseous soils and the effect of water percolation on co llapsibility of this soil. In this research, more than five sites where chosen to extract the gypseous soil samples with different gypsum content;  the  sites  located  in  different  regions  in  Salah  Aldeen  Governorate.  In  order  to  estimate  the settlement and collapse of gypseous soils, field tests consist of standard penetration test for depths (1m to 5m) for each site and plate load test were conducted in dry and soaked cases.The results show that the settlement of gypseous soils in dry condition is less than the same soils that have  low  values  of  gypsum  in  its  formation,  the  settlement  value  of  lightly  gypseous  soils  can  be evaluated from the basic equations depending on data of SPT. In soaking case with short term flooding, gypseous soils shows compressible  and they are sufficiently reliable soil base, while in the case of long term flooding settlement develops due to dissolution of salts and  gypsum. The  magnitude  and  the  rate  of  the  settlement  depend  on  initial  gypsum  content,  relative amount of leached salts, the mineralogy and type of soil and soil properties and acting load. The standard penetration test does not use in calculating the settlement for the soils that have gypsum in its formation in soaking condition.