In this paper, we consider the stability of a slope of 10 meters in silty gravel soils with modeling in the Geostudio Software. we intend to use the parameters of the volumetric water content and suction dependent permeability and provides relationships and graphs using the parameters obtained from gradation tests and Atterberg’s limits. Also, different conditions of the soil will be investigated, including: checking the factor of safety and deformation rates and pore water pressure in drained, non-drained and unsaturated conditions, as well as the effect of reducing the water level on other parameters. For this purpose, it is assumed that the groundwater level is at a depth of 2 meters from the ground. Then, with decreasing water level, the safety factor of slope stability was investigated and it was observed that with decreasing water level, the safety factor increased.
 Zhang, L. M., and Chen, Q, “Predicting bimodal soil-water characteristic curves,” J. Geotech. Geoenviron. Eng., 2005, 131(5), 666 670.
 X. Li, L. M. Zhang, and J. H. Li. “Development of a Modified Axis Translation Technique for Measuring SWCCs for Gravel Soils at Very Low Suctions,” Geotechnical Testing Journal, 2009, Vol. 32, No. 6.
 Fredlund DG, Xing A, Fredlund MD, Barbour SL. “The relationship of the unsaturated soil shear strength to the soil– water characteristic curve,” Can Geotech J., 1995, 33:440–8.
 Kamal Mohamed, “Effect of percentage of low plastic fines on the unsaturated shear strength of compacted gravel soil,” Ain Shams Engineering Journal., 2015, 6, 413–419.
 Fredlund, D. G. and Rahardjo, H., “Soil Mechanics for Unsaturated Soils,” JohnWiley and Sons, 1993, NewYork.
 Fetter, C. W. “Contaminant Hydrogeology,” Macmillan, 1995, New York.
 Ng, C. W. W., and Shi, Q. “Numerical investigation of the stability of unsaturated soil slopes subjected to transient seepage,” Computers and Geotechnics. ,1998, 22(1):660 1-28.
 Tsaparas, I., Rahardjo, H., Toll, D. G., and Leong, E. C. “Controlling parameters for rainfall-induced landslides,” Computers and Geotechnics., 2002, 29(1): 1-27.
 Rahardjo, H., Ong, T. H., Rezaur, R. B., and Leong, E. C. “Factors controlling instability of homogeneous soil slopes under rainfall,” Journal of Geotechnical and Geoenvironmental Engineering., 2007, 133(12): 1532-1543.
 Zhang, L. L., Fredlund, D. G., Zhang, L. M., and Tang, W. H. “Numerical study of soil conditions under which matric suction can be maintained,” Canadian Geotechnical Journal., 2004, 41(4): 569-582.