Document Type : Research Paper


Civil Engineering Dept., University of Technology-Iraq, Alsina’a street, 10066 Baghdad, Iraq.


This study aims to increase the bearing capacity of the soil by using geosynthetics in a single, double, or triple distribution pattern. The gypseous soil samples were brought from a site near Sawa Lake in Al-Muthanna Governorate with a gypsum content of about (37%), the Soil-Model apparatus of dimensions (60 × 60 × 50) cm with the proposed square footing of dimensions (10 × 10) cm are used in the experimental program of this study. To achieve this goal, a series of (48) different model tests were used on gypseous soil subjected to vertical stress in both dry and wet (saturation) conditions. Depending on the results of load-settlement curves relationships, the ultimate bearing capacity of dry and wet gypseous soil models was determined using the Two Tangent Intersection technique. The results also showed that the number of geotextile layers and the relative density of the gypseous soil samples significantly impact the improvement of the bearing capacity of gypseous soil models. Furthermore, the results showed that the improvement ratio in bearing capacity (BCR%) for gypseous soil models tested after being reinforced with geotextile layer for dry and wet (saturation)  at relative density (RD) of 30% and  60%  in single, double and triple distribution pattern. The percentage of the improvement in the wet case was higher than in the dry case. It was 143 % in the wet case when using triple-layer geotextile at different depths of reinforcement, while it was 96 % in the dry case.

Graphical Abstract


  • The bearing capacity ratio of gypseous soil was improved using different geotextile reinforcement patterns.
  • The maximum degree of improvement of gypseous model soil was achieved using a triple-layer at depth (0.5B+1B+1.5B)  of geotextile reinforcement with the wet case.
  • Increasing the number of geotextile reinforcement layers increases the ultimate bearing capacity values of for Gypseous Soil model.


Main Subjects

[1] Q. A.J.  Al-Obaidi, Hydro-Mechanical Behaviour of Collapsible Soils”, Ph.D. thesis, Ruhr-Universität Bochum, Germany, (2014).
[2] A. A Al-Mufty, Effect of gypsum dissolution on the mechanical behavior of gypseous soils, Ph.D. thesis University of Baghdad, Iraq, (1997).
[3] S.S. Razouki, Al- Omari, R.R., Nashat, I.H., Razouki H.F. and Khalid, S. (1994), The problems of Gypsiferous Soils in Iraq Proc Symposium on Gypseous Soils and their Effects on Structures,  NCCL, Baghdad.
[4] S. H. Abid-Awn, Improvement of gypseous soils using locally manufactured reinforcement materials, Ph. D Thesis,  Building and Construction Department, University of Technology, Baghdad, Iraq, (2004).
[5] A. El Howayek, , Identification and Behavior of Collapsible Soils,  Joint Transportation Research Program, report, Indiana. Engineering,  Journal of Boston Society of Civil Engineers.,  19 (2011) 168-209. doi: 10.5703/1288284314625
[6] ASTM D 2216,  Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil,  Rock and Soil-Aggregate Mixtures,(1998).
[7] . ASTM D 422, Standard test method for particle size analysis of soils, (ASTM International, West Conshohocken, PA, United States, (2000).
[8] ASTM D 854, Standard test methods for specific gravity of soil solids by water Pycnometer, (ASTM International, West Conshohocken, PA, United States, (2002).
[9] ASTM D 1557, , Standard test methods for laboratory compaction characteristics of soil using modified effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3)),  (ASTM International, West Conshohocken, PA, United States, 2000).ASTM D 4254, Standard Test Method for Minimum Index Density and Unit Weight of Soils and Calculation of Relative Density, American Society of Testing and Materials,(2000).
[10] ASTM D3080, Standard Test Method for Direct Shear Test of Soils under Consolidated Drained Conditions, American Society of Testing and Materials, (1998) .
[11] J. Han, principle and practice of ground improvement,  John. Wiley and Sons, Inc, Hoboken, New Jersey, 2015.
[12] S. K. Pokharel, Experimental study on geocell-reinforced bases under static and dynamic loading,   Doctoral dissertation, University of Kansas,  2010.
[13] M. K. Bera, , J. Song, K. Kakushima, P. Ahmet, K. Tsutsui, N. Sugii, and H. Iwai, Electrical Properties of Lanthanum-scandate Gate Dielectric Directly Deposited on Ge, E.C.S Transactions., 25(2009) 67-77.
[14] S. Alamshahi, N. Hataf , Bearing capacity of strip footings on sand slopes reinforced with geogrid and gridanchor, Geotextiles and Geomembranes ., 27(2009) 217– 226.
[15] Tg, S., and Sireesh, S, Behavior of Embedded Footings Supported on Geogrid Cell Reinforced Foundation Beds,Geotechnical Testing Journal., 28 (2012) 452-463.
[16] R. J.Bathurst, D. J.Benjamin, and P. M Jarrett, , Laboratory study of geogrid reinforced soil wall In Symposium on Geosynthetics for Soil Improvement,  ASCE ConventionAmerican Society of Civil Engineers (No. Geotechnical Special), (1998).
[17]  H. J Yang, S. K. Pokharel, Manandhar, C., Parsons, R. L., Leshchinsky, D., and Halahmi, I., “  Accelerated pavement testing of unpaved roads with geocell-reinforced sand bases’’,   Geotextiles and Geomembranes, 32(2012) 95-103.