N. Janbu, L. Bjerrum, and B. Kjaernsli, “Methods of Determining Elastic Settlement under Undrained Conditions” NGI Publication No. 16 Norwegian Geotechnical Institute, Oslo, 1956.
 J. H. Schmertmann, “Static Cone to Compute Static Settlement over Sand”, ASCE Journal of Soil Mechanics & Foundations Division, 96 (3), pp. 1011- 1043., 1970.
 K. Terzaghi, and R.B. Peck, “Soil Mechanics in Engineering Practice”, John Wiley and Sons, New York, 512p., 1948.
 R. B. Peck and A. Bazarra, Discussion of “Settlement of Spread Footings on Sands”, by D’Appolonia and Brisette, Journal of Soil Mechanics and Foundations Division, ASCE, 95(3), pp. 905–909, 1969.
 G.G. Meyerhof, “Ultimate Bearing Capacity of Footing on Sand Layer Overlying Clay”. Canadian Geotechnical Journal, vol. 11, pp. 223-229, 1974.
 Z. M. Mansour, Z. Chik, and M. R. Taha, “On Soil Collapse Potential Evaluation”, Asian Network for Scientific Information, Journal of Applied Sciences, Vol.8, No.23, pp. 4434-4438, 2008.
Tikrit Journal of Engineering Sciences (2016) 23(1) 20- 31
Settlement and Collapse of Gypseous Soils
|Ahmed A. H. Al-Obaidi||Ibtihal H. S. Al-Mafragei|
|Civil Eng. Dept., Tikrit University, Iraq|
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 collapsibility 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.
Keywords:Gypseous soils, Settlement, Collapsibility, SPT, PLT.