Unsaturated behaviour of gypseous sand soils using a modified triaxial test apparatus

ABSTRACT

This paper presents laboratory experiments on the effect of matric suction on the compressibility of unsaturated gypsum sand soil. The samples were obtained from Al-Najaf city in Iraq with gypsum contents of 14%, 22%, and 29%. Two series of laboratory tests were conducted. The first one is loading-path likes when a building is constructed on these soils in a specific degree of saturation (specific matric suction). Four matric suctions were adopted; 100, 60, 30, and zero percentages of initial matric suction under two confining stresses; 100 kPa and 200 kPa. Also, two saturated tests (CD) were performed under the aforementioned confining stresses. The second method is wetting-path, likes when a structure has been constructed and the degree of saturation of a foundation soil increases (decreasing in matric suction). The results from both paths revealed that the volumetric strains were increased by decreasing the matric suction and increasing the gypsum content..

KEYWORDS:

• Al-Najaf
• gypsum sand soil
• modified triaxial cell
• volumetric strains
• matric suction

Acknowledgments

The research described in this paper was supported by laboratory of Ferdowsi University of Mashhad (FUM). Special thanks are due to the staff of the soil mechanic laboratory. I am especially grateful for the efforts of my friend Rasouli who helped me to complete this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Declaration

No conflict of interest.

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Notes on contributors

Mustafa Abdalhusein

Dr Mustafa Abdalhusein is the department head of Civil Engineering of Almaaqal University and a geotechnical designer. He received his bachelor’s and master’s degrees from the University of Kufa and earned his Ph.D. degree from Ferdowsi University of Mashhad in Geotechnical Engineering. His area of interest is soil mechanics and hydraulic structures. Besides, soil testing, unasturated state, soil improvement, soil interaction modeling using geotechnical software are his major research interests.

Ali Akhtarpour

Dr Ali Akhtarpour was graduated from Polytechnic University of Tehran in BSc of civil engineering, MSc (Under supervision of Dr Abbas Soroush) and PhD (Under supervision of Dr Ali Khodaii) of geotechnical engineering in 2000, 2003 and 2011 respectively. Now he is a staff member (Assistant Prof.) of engineering faculty in the Ferdowsi University of Mashhad. Also he has some experiences on the embankment dam design, monitoring and numerical modelling for more than 18 years. His research interests include geotechnical earthquake engineering and numerical investigations into geotechnical problems with regard to infrastructure such as dams, foundations , excavations and unsaturated soil. You can also find more about publications and interesting subject area in his personal homepage as below:http://akhtarpour.profcms.um.ac.ir/

Mohammed Mahmood

Prof. Dr. Mohammed Sh. Mahmood was graduated from University of Babylon, Iraq in BSc of civil engineering, 1995. MSc and PhD from ‘University of Technology, Iraq, 2000, 2007 respectively and both under supervision of Prof. Dr. Namir Kh. Al- Al-Saoudi.Now he is a faculty member of faculty of engineering in the University of Kufa, Iraq. You can find more about publications and interesting subject area in his personal homepage: http://staff.uokufa.edu.iq/en/index.php?mohammedsh.alshakarchi